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JSON Meta Application Protocol (JMAP)

This document specifies the core protocol for synchronising JSON-based data objects efficiently, with support for push and out-of-band binary data upload/download.

This is then built upon to provide mail, contacts and calendar synchronisation protocols.

Introduction

JMAP is a generic protocol for synchronising data, such as mail, calendars or contacts, between a client and a server. It is optimised for mobile and web environments, and aims to provide a consistent interface to different data types.

This specification is for the generic mechanism of authentication and synchronisation. Further specifications define the data models for different data types that may be synchronised via JMAP.

JMAP is designed to make efficient use of limited network resources. Multiple API calls may be batched in a single request to the server, reducing round trips and improving battery life on mobile devices. Push connections remove the need for polling, and an efficient delta update mechanism ensures a minimum of data is transferred.

JMAP is designed to be horizontally scalable to a very large number of users. This is facilitated by the separate end points for users after login, the separation of binary and structured data, and a shared data model that does not allow data dependencies between accounts.

Notational Conventions

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [@!RFC2119].

The underlying format used for this specification is JSON. Consequently, the terms “object” and “array” as well as the four primitive types (strings, numbers, booleans, and null) are to be interpreted as described in Section 1 of [@!RFC7159].

Some examples in this document contain “partial” JSON documents used for illustrative purposes. In these examples, three periods “…” are used to indicate a portion of the document that has been removed for compactness.

Types signatures are given for all JSON objects in this document. The following conventions are used:

The Number datatype

The JSON datatypes are limited to those found in JavaScript. A Number in JavaScript is represented as a signed double (64-bit floating point). However, except where explicitly specified, all numbers used in this API are unsigned integers <= 2^53 (the maximum integer that may be reliably stored in a double). This implicitly limits the maximum length of message lists in queries and the like.

The Date datatypes

Where a JMAP API specifies Date as a type, it means a string in [@!RFC3339] date-time format, with the time-offset component always Z (i.e. the date-time MUST be in UTC time) and time-secfrac always omitted. The “T” and “Z” MUST always be upper-case. For example, "2014-10-30T14:12:00Z".

JSON as the data encoding format

JSON is a text-based data interchange format as specified in [@!RFC7159]. The I-JSON format defined in [@!RFC7493] is a strict subset of this, adding restrictions to avoid potentially confusing scenarios (for example, it mandates that an object MUST NOT have two properties with the same key).

All data sent from the client to the server or from the server to the client (except binary file upload/download) MUST be valid I-JSON according to the RFC, and is therefore case-sensitive and encoded in UTF-8 ([@!RFC3629]).

Terminology

User

A user represents a set of permissions relating to what data can be seen. To access data in JMAP, you first authenticate as a particular user.

Accounts

An account is a collection of data.

All data, other than the Account objects themselves, belong to a single account. A single account may contain an arbitrary set of data, for example a collection of mail, contacts and calendars. Most operations in JMAP are isolated to a single account; there are a few explicit operations to copy data between them. Certain properties are guaranteed for data within the same account, for example uniqueness of ids within a type in that account.

An account is not the same as a user, although it is common for the primary account to directly belong to the user. For example, you may have an account that contains data for a group or business, to which multiple users have access. Users may also have access to accounts belonging to another user if that user is sharing some of their data.

Data types and records

JMAP provides a uniform interface for creating, retrieving, updating and deleting various types of objects. A data type is a collection of named, typed properties, just like the schema for a database table. Each instance of a data type is called a record.

Ids

All object ids are assigned by the server, and are immutable. They MUST be unique among all objects of the same type within the same account. Ids may clash across accounts, or for two objects of different types within the same account.

Ids are always Strings. An id MUST be a valid UTF-8 string of at least 1 character in length and maximum 256 bytes in size, but MUST NOT start with the # character, as this is reserved for doing back references during object creation (see the setFoos description).

The JMAP API model

JMAP uses HTTP [@!RFC7230] to expose API, Push, Upload and Download resources. Implementations MUST support HTTP/1.1, and MAY support later versions. Support for common HTTP mechanisms such as redirection and caching are assumed.

Clients SHOULD understand and be able to handle standard HTTP status codes appropriately.

All data exchanges are authenticated using an access token. Authentication is covered in section 2.

An authenticated client may exchange data with the server using four different mechanisms:

  1. The client may make an API request to the server to get or set structured data. This request consists of an ordered series of method calls. These are processed by the server, which then returns an ordered series of responses. This is described in section 3.
  2. The client may download binary files from the server. This is detailed in section 4.
  3. The client may upload binary files to the server. This is specified in section 5.
  4. The client may connect to a push channel on the server, to be notified when data has changed. This is explained in section 6.

Authentication

When connecting to any JMAP server, the client must first gain an access token. It cannot just use a username/password directly. This allows the server to know (and show the user) which clients currently have access to the account, and to be able to revoke access individually.

The server may support multiple different mechanisms for authenticating a user to gain the access token. It is expected that further types may be added in future extensions to the JMAP specification.

Service autodiscovery

To begin authentication, the client needs to know the authentication URL for the JMAP server.

There are two standardised autodiscovery methods in use for internet protocols:

A JMAP-supporting host for the domain example.com SHOULD publish a SRV record _jmaps._tcp.example.com which gives a hostname and port (usually port 443). The authentication URL is then https://${hostname}[:${port}]/.well-known/jmap (following any redirects).

If the client has a username in the form of an email address, it MAY use the domain portion of this to attempt autodiscovery of the JMAP server.

To support clients that are unable to do SRV lookups, the server SHOULD make the hostname the same domain as the username if possible.

Getting an access token

Authorization always starts with the client making a POST request to the authentication URL (found either via service autodiscovery or manual entry). The request MUST be of type application/json and specify an Accept: application/json header. The body of the request MUST be a single JSON object, encoded in UTF-8, with the following properties:

The server may use the client/device information to help identify the login to the user in a login log or other security reporting. Although hopefully unnecessary, they may also be helpful for working around client bugs in the future.

The server will respond with one of the following HTTP status codes:

200: Success, but more authorization required.

The response body will be a single JSON object with the following properties.

This is the standard response to an initial request. Note, a server may return this even if the username is not actually active, to prevent enumeration. The client should then pick one of the methods from the list in the response to continue with authentication (if no methods supported by the client are in the list, it will not be able to get an access token).

An AuthMethod object MUST have a type property. This is a String representing the method of authentication. For some types, there may be other values required on the AuthMethod object in addition; see the description of types below. The following types are currently defined, but more may be added in the future. A client SHOULD offer the user the option to choose any of the method types returned that the client supports. The client MUST ignore any types it does not understand:

If not using "oauth", the user will at some point indicate to the client to continue authentication (after inputing any required token/code/password dependent on the auth method chosed). At this point the client submits a POST request to the same URL as before, with the body being a single JSON object with the following properties:

Note: The client SHOULD NOT store any password/code the user has entered beyond what is required to submit it to the server in this step.

The server will then return one of the same set of responses as before, which should be handled the same (for example, if two-factor authentication is required, a 200 response may be returned again and TOTP/U2F prompted for).

If the user chooses to authenticate using SMS, they may need to request the server to send the code to a particular number before they can submit a code. To do this, the client submits a POST request to the same URL as before, with the body being a single JSON object with the following properties:

The server SHOULD send the code to the given phone if the phone id is valid. If the code has already been sent, it is server-dependent whether it is sent again or ignored. The server MUST return one of the same set of responses as before, which should be handled the same (in most cases this will be a 200 response identical to before except that the isCodeSent property for the phone will now be true).

201: Authentication is complete, access token created.

The response body will be a single JSON object with the following properties.

URLs are returned only after logging in. This allows different URLs to be used for users located in different geographic datacentres within the same service.

Note, if authentication is done via IP or mobile subscriber ID or some similar mechanism, a 201 response MAY be returned in response to the initial request (with just the username and client info).

400: Malformed request

The request is of the wrong content type, or does not contain data in the expected format. The client MUST NOT retry the same request. There is no content in the response.

403: Authentication step failed, but client may try again

Returned in response to a continuation request which failed (e.g. the password entered was not correct, or the out-of-band step was not completed successfully). The response body will be a single JSON object with the same properties as the 200 response, and the client may try again.

404: Not found

The JMAP authentication server is not available at this address. The client needs to rediscover the authentication URL. There is no content in the response.

410: Restart authentication

The login attempt has failed permanently. This may be due to a password being incorrect, the login id expiring, or any other reason. The client MUST restart authentication (go back to sending the username and client info to the server). There is no content in the response.

429: Rate limited

Returned if the server is temporarily blocking this IP/client from authenticating. This may be due to too many failed password attempts, or detected username enumeration attempts, or any other reason. (Legitimate) clients should wait a while then try again. There is no content in the response.

500: Internal server error

Something has gone wrong internally, and the server is in a broken state. Don’t automatically retry. There is no content in the response.

503: Service unavailable

The server is currently down. Try again later with exponential backoff. There is no content in the response.

Refetching URL endpoints

A server MAY (although SHOULD NOT) move end points for any services other than authentication at any time. If a request to the API/file upload/event source endpoint returns a 404, the client MUST refetch the URL endpoints. To do this, it should make an authenticated GET request to the authentication URL (see below for how to authenticate requests).

For OAuth logins, this is how the URLs may be fetched initially as well.

The server MUST respond with one of the following status codes:

201: Authentication is complete, access token created.

The request was successful. The response will be of type application/json and consists of a single JSON object containing the following properties:

403: Restart authentication

The Authorization header was missing or did not contain a valid token. Reauthenticate and then retry the request. There is no content in the response.

404: Not found

The JMAP server is no longer here. There is no content in the response.

500: Internal server error

Something has gone wrong internally, and the server is in a broken state. Don’t automatically retry. There is no content in the response.

503: Service unavailable

The server is currently down. Try again later with exponential backoff. There is no content in the response.

Revoking an access token

The validity of an access token is determined by the server. It may be valid for a limited time only, or expire after a certain time of inactivity, or be valid indefinitely etc. If an access token expires, it MUST NOT be resurrected. The client MUST restart the authentication process to get a new access token.

For OAuth, see the provider’s documentation on revoking access tokens.

Otherwise, a client may revoke an access token at any time by making an authenticated DELETE HTTP request to the authentication URL (the one used to get the token in the first place). The response from the server will be one of the following:

204: Success

The access token has now been revoked. There is no content in the response.

401: Unauthorized

Failed due to missing Authorization header, or the Authorization header did not contain a valid access token. As per the HTTP spec, the response MUST have a WWW-Authenticate: Bearer header. There is no content in the response.

Authenticating HTTP requests

All HTTP requests other than to the authentication URL must be authenticated. To do this, the client MUST add an Authorization header to each request.

Once authenticated, the client will have an access token. This is used with the Bearer scheme as specified in [@!RFC6750] to authenticate HTTP requests.

For example, if user@example.com successfully logged in and the client received an accessToken of abcdef1234567890, to authenticate requests you would add the following header:

Authorization: Bearer abcdef1234567890

Signed GET requests

Sometimes, particularly in the browser context, authenticating a GET request using the usual Authorization header is not easily implemented. In such situations, a client may use a signed request instead.

Instead of the Authorization header, a signed request has an access_token query parameter, the value of which is an [@!RFC7519] JSON Web Token constructed as follows:

To verify, a server MUST:

The server MAY choose to only allow tokens to be valid for a limited amount of time after the client created it, as determined by the iat claim.

Structured data exchange

The client may make an API request to the server to get or set structured data. This request consists of an ordered series of method calls. These are processed by the server, which then returns an ordered series of responses.

Making an API request

To make an API request, the client makes an authenticated POST request to the API resource; see the Authentication section of the spec for how to discover this URL and how to authenticate requests.

The request MUST have a content type of application/json and be encoded in UTF-8.

If successful, the response will be of type application/json and consist of the response to the API calls, as described below.

The structure of an API request

The client initiates an API request by sending the server a JSON array. Each element in this array is another array representing a method invocation on the server. The server will process the method calls and return a response consisting of an array in the same format. Each method call always contains three elements:

  1. The name of the method to call, or the name of the response from the server. This is a String.
  2. An Object containing named arguments for that method or response.
  3. A client id: an arbitrary String to be echoed back with the responses emitted by that method call (as we’ll see lower down, a method may return 1 or more responses, as some methods make implicit calls to other ones).

Example query:

[
  ["method1", {"arg1": "arg1data", "arg2": "arg2data"}, "#1"],
  ["method2", {"arg1": "arg1data"}, "#2"],
  ["method3", {}, "#3"]
]

The method calls MUST be processed sequentially, in order. Each API request (which, as shown, may contain multiple method calls) receives a JSON response in exactly the same format. The output of the methods MUST be added to the array in the same order as the methods are processed.

Example response:

[
  ["responseFromMethod1", {"arg1": 3, "arg2": "foo"}, "#1"],
  ["responseFromMethod2", {"isBlah": true}, "#2"],
  ["anotherResponseFromMethod2", {
    "data": 10,
    "yetmoredata": "Hello"
  }, "#2"],
  ["aResponseFromMethod3", {}, "#3"]
]

Use of null

Unless otherwise specified, a missing property in the arguments object of a request (from the client), or a response (from the server) MUST be intepreted exactly the same as that property having the value null.

Unless otherwise specified, a missing property in a data object MUST be interpreted in the following ways:

For network efficiency when fetching, the server and client may make use of the above and omit properties which have the default value for the data type.

Errors

If the data sent as an API request is not valid JSON or does not match the structure above, a 400 Bad Request error will be returned at the HTTP level.

Possible errors for each method are specified in the method descriptions. If a method encounters an error, the appropriate error response MUST be inserted at the current point in the output array and, unless otherwise specified, further processing MUST NOT happen within that method call.

Any further method calls in the request MUST then be processed as normal.

An error response looks like this:

["error", {
  type: "unknownMethod"
}, "client-id"]

The response name is error, and it has a type property as specified in the method description. Other properties may be present with further information; these are detailed in the method descriptions where appropriate.

Any method MAY return an error of type serverError if an unexpected or unknown error occurs during the processing of that call. The state of the server after such an error is undefined.

If an unknown method is called, an unknownMethod error (this is the type shown in the example above) MUST be inserted and then the next method call MUST be processed as normal.

If an unknown argument or invalid arguments (wrong type, or in violation of other specified constraints) are supplied to a method, an invalidArguments error MUST be inserted and then the next method call MUST be processed as normal.

Vendor-specific extensions

Individual services will have custom features they wish to expose over JMAP. This may take the form of extra datatypes and/or methods not in the spec, or extra arguments to JMAP methods, or extra properties on existing data types (which may also appear in arguments to methods that take property names). To ensure compatibility with clients that don’t know about a specific custom extension, and for compatibility with future versions of JMAP, the server MUST ONLY expose these extensions if the client explicitly opts in. Without opt-in, the server MUST follow the spec and reject anything that does not conform to it as specified.

Security

As always, the server must be strict about data received from the client. Arguments need to be checked for validity; a malicious user could attempt to find an exploit through the API. In case of invalid arguments (unknown/insufficient/wrong type for data etc.) the method MUST return an invalidArguments error and terminate.

Concurrency

Each individual method call within a request MUST be serializable; concurrent execution of methods MUST produce the same effect as running them one at a time in some order.

This means that the observable ordering may interleave method calls from different concurrent API requests, such that the data on the server may change between two method calls within a single API request.

Standard methods and naming convention

JMAP provides a uniform interface for creating, retrieving, updating and deleting objects of a particular type. For a Foo data type, records of that type would be fetched via a getFoos call and modified via a setFoos call. Delta updates may be fetched via a getFooUpdates call. These methods all follow a standard format as described below.

Methods with a name starting with get MUST NOT alter state on the server.

getFoos

Objects of type Foo are fetched via a call to getFoos.

It takes the following arguments:

The response to getFoos is called foos. It has the following arguments:

The following error may be returned instead of the foos response:

accountNotFound: An accountId was explicitly included with the request, but it does not correspond to a valid account.

accountNotSupportedByMethod: The accountId given corresponds to a valid account, but the account does not support this data type.

requestTooLarge: The number of ids requested by the client exceeds the maximum number the server is willing to process in a single method call.

invalidArguments: One of the arguments is of the wrong type, or otherwise invalid. A description property MAY be present on the response object to help debug with an explanation of what the problem was.

getFooUpdates

When the state of the set of Foo records changes on the server (whether due to creation, updates or deletion), the state property of the foos response will change. The getFooUpdates call allows a client to efficiently update the state of its Foo cache to match the new state on the server. It takes the following arguments:

The response to getFooUpdates is called fooUpdates. It has the following arguments:

If a maxChanges is supplied, or set automatically by the server, the server MUST ensure the number of ids returned across changed and removed does not exceed this limit. If there are more changes than this between the client’s state and the current server state, the update returned SHOULD generate an update to take the client to an intermediate state, from which the client can continue to call getMessageUpdates until it is fully up to date. If it is unable to calculate an intermediate state, it MUST return a cannotCalculateChanges error response instead.

If a Foo record has been modified AND deleted since the oldState, the server SHOULD just return the id in the removed response, but MAY return it in the changed response as well. If a Foo record has been created AND deleted since the oldState, the server SHOULD remove the Foo id from the response entirely, but MAY include it in the removed response.

The following errors may be returned instead of the fooUpdates response:

accountNotFound: An accountId was explicitly included with the request, but it does not correspond to a valid account.

accountNotSupportedByMethod: The accountId given corresponds to a valid account, but the account does not support this data type.

invalidArguments: The request does not include one of the required arguments, or one of the arguments is of the wrong type, or otherwise invalid. A description property MAY be present on the response object to help debug with an explanation of what the problem was.

cannotCalculateChanges: The server cannot calculate the changes from the state string given by the client. Usually due to the client’s state being too old, or the server being unable to produce an update to an intermediate state when there are too many updates. The client MUST invalidate its Foo cache.

Maintaining state to allow calculation of getFooUpdates can be expensive for the server, but always returning cannotCalculateChanges severely increases network traffic and resource usage for the client. To allow efficient sync, servers SHOULD be able to calculate changes from any state string that was given to a client within the last 30 days (but of course may support calculating updates from states older than this).

setFoos

Modifying the state of Foo objects on the server is done via the setFoos method. This encompasses creating, updating and destroying Foo records. This has two benefits:

  1. It allows the server to sort out ordering and dependencies that may exist if doing multiple operations at once (for example to ensure there is always a minimum number of a certain record type).
  2. A single call can make all the changes you want to a particular type. If the client wants to use ifInState to guard its changes, it is only possible for it to make one call that modifies any particular type per request, since it will need the new state following that call to make the next modification.

The setFoos method takes the following arguments:

Each creation, modification or destruction of an object is considered an atomic unit. It is permissible for the server to commit changes to some objects but not others, however it is not permissible to only commit part of an update to a single record (e.g. update a name property but not a count property, if both are supplied in the update object).

The final state MUST be valid after the setFoos is finished, however the server may have to transition through invalid intermediate states (not exposed to the client) while processing the individual create/update/destroy requests. For example, suppose there is a “name” property that must be unique. A single method call could rename an object A => B, and simultaneously rename another object B => A. The final state is valid, so this is allowed, however if processed sequentially there will be an internal state where temporarily both objects have the same name.

If a create, update or destroy is rejected, the appropriate error MUST be added to the notCreated/notUpdated/notDestroyed property of the response and the server MUST continue to the next create/update/destroy. It does not terminate the method.

If an id given cannot be found, the update or destroy MUST be rejected with a notFound set error.

Some record objects may hold references to others (foreign keys). When records are created or modified, they may reference other records being created in the same API request by using the creation id prefixed with a #. The order of the method calls in the request by the client MUST be such that the record being referenced is created in the same or an earlier call. The server thus never has to look ahead. Instead, while processing a request (a series of method calls), the server MUST keep a simple map for the duration of the request of creation id to record id for each newly created record, so it can substitute in the correct value if necessary in later method calls.

Creation ids are scoped by type; a separate creation id -> id map MUST be kept for each type for the duration of the request. Foreign key references are always for a particular record type, so use of the same creation key in two different types cannot cause any ambiguity. Creation ids sent by the client SHOULD be unique within the single API request for a particular data type. If a creation id is reused for the same type, the server MUST map the creation id to the most recently created item with that id.

The response to setFoos is called foosSet. It has the following arguments:

A SetError object has the following properties:

The following SetError types are defined and may be returned for set operations on any record type:

Other possible SetError types MAY be given in specific method descriptions. Other properties MAY also be present on the SetError object, as described in the relevant methods.

The following errors may be returned instead of the foosSet response:

accountNotFound: An accountId was explicitly included with the request, but it does not correspond to a valid account.

accountNotSupportedByMethod: The accountId given corresponds to a valid account, but the account does not support this data type.

accountReadOnly: The account has isReadOnly == true.

requestTooLarge: The total number of objects to create, update or destroy exceeds the maximum number the server is willing to process in a single method call.

invalidArguments: One of the arguments is of the wrong type, or otherwise invalid. A description property MAY be present on the response object to help debug with an explanation of what the problem was.

stateMismatch: An ifInState argument was supplied and it does not match the current state.

getFooList

For data sets where the total amount of data is expected to be very small, clients can just fetch the complete set of data and then do any sorting/filtering locally. However, for large data sets (e.g. multi-gigabyte mailboxes), the client needs to be able to perform a query on the server for the data type.

A query on the set of Foos in an account is made by calling getFooList. This takes a number of arguments to determine which records to include, how they should be sorted, and which part of the result should be returned (the full list may be very long). The result is returned as a list of Foo ids. Optionally, the records themselves may be fetched at the same time.

A call to getFooList takes the following arguments:

The response to a call to getFooList is called fooList. It has the following arguments:

The following errors may be returned instead of the fooList response:

accountNotFound: An accountId was explicitly included with the request, but it does not correspond to a valid account.

accountNotSupportedByMethod: The accountId given corresponds to a valid account, but the account does not support this data type.

invalidArguments: The request does not include one of the required arguments, or one of the arguments is of the wrong type, or otherwise invalid. A description property MAY be present on the response object to help debug with an explanation of what the problem was.

getFooListUpdates

The getFooListUpdates call allows a client to efficiently update the state of any cached foo list to match the new state on the server. It takes the following arguments:

The response to getFooListUpdates is called fooListUpdates It has the following arguments:

The result of this should be that if the client has a cached sparse array of foo ids in the list in the old state:

fooIds = [ "id1", "id2", null, null, "id3", "id4", null, null, null ]

then if it splices out all foos in the removed array:

removed = [ "id2", … ];
fooIds => [ "id1", null, null, "id3", "id4", null, null, null ]

and splices in (in order) all of the foos in the added array:

added = [{ fooId: "id5", index: 0, … }];
fooIds => [ "id5", "id1", null, null, "id3", "id4", null, null, null ]

then the foo list will now be in the new state.

The following errors may be returned instead of the fooListUpdates response:

accountNotFound: An accountId was explicitly included with the request, but it does not correspond to a valid account.

accountNotSupportedByMethod: The accountId given corresponds to a valid account, but the account does not support this data type.

invalidArguments: The request does not include one of the required arguments, or one of the arguments is of the wrong type, or otherwise invalid. A description property MAY be present on the response object to help debug with an explanation of what the problem was.

tooManyChanges: There are more changes the the client’s maxChanges argument. Each item in the removed or added array is considered as one change. The client may retry with a higher max changes or invalidate its cache of the foo list.

cannotCalculateChanges: The server cannot calculate the changes from the state string given by the client. Usually due to the client’s state being too old. The client MUST invalidate its cache of the foo list.

Binary data

Binary data is referenced by a blobId in JMAP, and uploaded/downloaded separately to the core API. A blobId does not have a name inherent to it, but this is normally given in the same object that contains the blobId. The data represented by a blobId is immutable.

Any blobId that exists within an account may be used when creating/updating another object in that account. For example, an Email type may have a blobId that represents the RFC5322 representation of the message. A client could create a new Email object with an attachment and use this blobId, in effect attaching the old message to the new one. Similarly it could attach any existing existing attachment of an old message without having to download and upload it again.

When the client uses a blobId in a create/update, the server MAY assign a new blobId to refer to the same binary data from the new/updated object. If it does so, it MUST return any properties that contain a changed blobId in the created/updated response so the client gets the new ids.

A blob that is not referenced by a JMAP object (e.g. as a message attachment), MAY be deleted by the server to free up resources. Uploads (see below) are initially unreferenced blobs. To ensure interoperability:

Uploading binary data

There is a single endpoint which handles all file uploads, regardless of what they are to be used for. To upload a file, the client submits an authenticated POST request to the file upload resource (see the authentication section for information on how to obtain this URL). The Content-Type MUST be correctly set for the type of the file being uploaded. The request MAY include an X-JMAP-AccountId header, with the value being the account to use for the request. Otherwise, the default account will be used.

A successful request MUST return a single JSON object with the following properties as the response:

If identical binary content to an existing blob in the account is uploaded, the existing blobId MAY be returned.

Downloading binary data

After completing authentication, the client will receive a downloadUrl as part of the response. This is in [@!RFC6570] URI Template (level 1) format. The URL MUST contain a variable called blobId, MAY contain a variable called accountId, and SHOULD contain a variable called name.

The client may use this template in combination with an accountId (if required in the URL template) and blobId to download any binary data (files) referenced by other objects. Since a blob is not associated with a particular name, the template SHOULD allow a name to be substituted in as well; the server will return this as the filename if it sets a Content-Disposition header.

To download the data the client makes an authenticated GET request to the download URL with the appropriate variables substituted in, and then follows any redirects. The client SHOULD send an Accept header with the content type they would like the server to return for the file. The Content-Type header of a successful response SHOULD be set to the type as requested in the Accept header by the client, or application/octet-stream if unknown and no Accept header given.

In situations where it’s not easy to authenticate the download request (e.g.: when downloading a file through a link in a HTML document), the client MAY use a signed GET request (see the authentication chapter for how to issue a signed request). Instead of specifying an Accept header, the client SHOULD add an accept query parameter to the signed URL, with the value being the content type to use for the response.

Push

Push notifications allow clients to efficiently update (almost) instantly to stay in sync with data changes on the server. In JMAP, push notifications occur out-of-band (i.e. not over the same connection as API exchanges), so that they can make use of efficient native push mechanisms on different platforms.

The general model for push is simple and sends minimal data over the push channel. The format allows multiple changes to be coalesced into a single push update, and the frequency of pushes to be rate limited by the server. It doesn’t matter if some push events are dropped before they reach the client; it will still get all changes next time it syncs.

The StateChange object

When something changes on the server, the server pushes a StateChange object to the client. A StateChange object has the following properties:

PushSubscription

A push subscription is a message delivery context established between the client and a push service. A PushSubscription object has the following properties:

Clients may register the push subscription with the JMAP server, which will then make a POST request to the associated push endpoint whenever an event occurs.

The POST request MUST have a content type of application/json and contain the utf-8 JSON encoded StateChange object as the body. The request MUST have a TTL header, and MAY have Urgency and/or Topic headers, as specified in section 5 of [@!RFC8030].

If the response code is 503 (Service Unavailable), the JMAP server MAY try again later, but may also just drop the event. If the response code is 429 (Too Many Requests) the JMAP server SHOULD attempt to reduce the frequency of pushes to that URL. Any other 4xx or 5xx response code MUST be considered a permanent failure and the push subscription should be deregistered (not tried again even for future events unless explicitly re-registered by the client).

The use of this push endpoint conforms with the use of a push endpoint by an Application Server as defined in [@!RFC8030]. A client MAY use the rest of [@!RFC8030] in combination with its own Push Server to form a complete end-to-end solution, or MAY rely on alternative mechanisms to ensure the delivery of the pushed data after it leaves the JMAP server.

setPushSubscription

Each session may only have a single push subscription registered. The push subscription is tied to the access token used to create it. Should the access token expire or be revoked, the push subscription MUST be removed by the JMAP server. The client MUST re-register the push subscription after reauthenticating to resume callbacks.

To set the push subscription, make a call to setPushSubscription. It takes the following argument:

The response to setPushSubscription is called pushSubscriptionSet. It has no arguments.

The following errors may be returned instead of the pushSubscriptionSet response:

invalidUrl: Returned if the URL does not begin with https://, or is otherwise syntactically invalid or does not resolve.

forbidden: Returned if the URL is valid, but for policy reasons the server is not willing to connect to it.

getPushSubscription

To check the currently set push subscription (if any), make a call to getPushSubscription. It does not take any arguments. The response is called pushSubscription and it has a single argument:

Event Source

Clients that can hold open TCP connections can connect directly to the JMAP server to receive push notifications via a text/event-stream resource, as described in http://www.w3.org/TR/eventsource/. This is a long running HTTP request down which the server can push data.

When a change occurs in the data on the server, it pushes an event called state to any connected clients, with the StateChange object as the data.

The server SHOULD also send a new event id that encodes the entire server state visible to the user immediately after sending a state event. When a new connection is made to the event-source endpoint, a client following the server-sent events specification will send a Last-Event-ID HTTP header with the last id it saw, which the server can use to work out whether the client has missed some changes. If so, it SHOULD send these changes immediately on connection.

The client MAY add a query parameter called closeafter with value state to the event-source resource URL when requesting the event-source resource. If set, the server MUST end the HTTP response after pushing a state event. This can be used by clients in environments where buffering proxies prevent the pushed data from arriving immediately, or indeed at all, when operating in the usual mode.

The client MAY add a query parameter called ping, with a positive integer value representing a length of time in seconds, e.g. ping=300. The server MAY modify the value given to be subject to a minimum and/or maximum value. For interoperability, servers MUST NOT have a minimum allowed value higher than 30 or a maximum allowed value less than 300.

If set, the server MUST send an event called ping whenever this time elapses since the previous event was sent. This MUST NOT set a new event id. The data for the event MUST be a JSON object containing an interval property, the value (type Number) being the interval in seconds the server is using to send pings (this may be different to the requested value if the server clamped it to be within a min/max value).

Clients can monitor for the ping event to help determine when the closeafter mode may be required.

Refer to the Authentication section of this spec for details on how to get the URL for the event-source resource. Requests to the resource must be authenticated.

A client MAY hold open multiple connections to the event-source resource, although it SHOULD try to use a single connection for efficiency.

Security Considerations

JSON parsing

The security considerations of [@!RFC7159] apply to the use of JSON as the data interchange format.

Denial of service

A small request may result in a very large response, and require considerable work on the server if resource limits are not enforced. JMAP provides mechanisms for advertising and enforcing a wide variety of limits for mitigating this threat, including limits on number of objects fetched in a single method call, number of methods in a single request, number of concurrent requests, etc.

JMAP servers MUST implement sensible limits to mitigate against resource exhaustion attacks.

Push encryption

When data changes, a small object is pushed with the new state strings for the types that have changed. While the data here is minimal, a passive man-in-the-middle attacker may be able to gain useful information. To ensure confidentiality, if the push is sent via a third party outside of the control of the client and JMAP server the client MUST specify encryption keys when establishing the PushSubscription.

The privacy and security considerations of [@!RFC8030] and https://tools.ietf.org/html/draft-ietf-webpush-encryption-09 also all apply to the use of the PushSubscription mechanism.