# Gerrit Code Review - REST API

version v2.8.3-3-gb9d00b0

Gerrit Code Review comes with a REST like API available over HTTP. The API is suitable for automated tools to build upon, as well as supporting some ad-hoc scripting use cases.

See also: REST API Developers' Notes.

## Endpoints

/access/

  Access Right related REST endpoints

/accounts/

  Account related REST endpoints

/changes/

  Change related REST endpoints

/config/

  Config related REST endpoints

/groups/

  Group related REST endpoints

/plugins/

  Plugin related REST endpoints

/projects/

  Project related REST endpoints

## Protocol Details

### Authentication

By default all REST endpoints assume anonymous access and filter results to correspond to what anonymous users can read (which may be nothing at all).

Users (and programs) may authenticate using HTTP authentication by supplying the HTTP password from the user’s account settings page. Gerrit by default uses HTTP digest authentication. To authenticate, prefix the endpoint URL with `/a/`. For example to authenticate to `/projects/` request URL `/a/projects/`.

### Preconditions

Clients can request PUT to create a new resource and not overwrite an existing one by adding `If-None-Match: *` to the request HTTP headers. If the named resource already exists the server will respond with HTTP 412 Precondition Failed.

### Output Format

Most APIs return pretty printed JSON by default. Compact JSON can be requested by setting the `Accept` HTTP request header to include `application/json`, for example:

      GET /projects/ HTTP/1.0
      Accept: application/json

JSON responses are encoded using UTF-8 and use content type `application/json`.

To prevent against Cross Site Script Inclusion (XSSI) attacks, the JSON response body starts with a magic prefix line that must be stripped before feeding the rest of the response body to a JSON parser:

      )]}'
      [ ... valid JSON ... ]

The default JSON format is pretty, which uses extra whitespace to make the output more readable for a human. Producing (and parsing) the non-pretty compact format is more efficient so tools should request it by using the `Accept: application/json` header or `pp=0` query parameter whenever possible.

Responses will be gzip compressed by the server if the HTTP `Accept-Encoding` request header is set to `gzip`. This may save on network transfer time for larger responses.

### Timestamp

Timestamps are given in UTC and have the format "yyyy-mm-dd hh:mm:ss.fffffffff" where "ffffffffff" indicates the nanoseconds.

### Encoding

All IDs that appear in the URL of a REST call (e.g. project name, group name) must be URL encoded.

### Response Codes

HTTP status codes are well defined and the Gerrit REST endpoints use them as described in the HTTP spec.

Here are examples for some HTTP status codes that show how they are used in the context of the Gerrit REST API.

#### 400 Bad Request

`400 Bad Request` is used if the request is not understood by the server due to malformed syntax.

E.g. `400 Bad Request` is returned if JSON input is expected but the Content-Type of the request is not application/json or the request body doesn’t contain valid JSON.

`400 Bad Request` is also used if required input fields are not set or if options are set which cannot be used together.

#### 403 Forbidden

`403 Forbidden` is used if the operation is not allowed because the calling user has no sufficient permissions.

E.g. some REST endpoints require that the calling user has certain global capabilities assigned.

`403 Forbidden` is also used if `self` is used as account ID and the REST call was done without authentication.

#### 404 Not Found

`404 Not Found` is returned if the resource that is specified by the URL is not found or is not visible to the calling user. A resource cannot be found if the URL contains a non-existing ID or view.

#### 405 Method Not Allowed

`405 Method Not Allowed` is used if the resource exists but doesn’t support the operation.

E.g. some of the `/groups/` endpoints are only supported for Gerrit internal groups, if they are invoked for an external group the response is `405 Method Not Allowed`.

#### 409 Conflict

`409 Conflict` is used if the request cannot be completed because the current state of the resource doesn’t allow the operation.

E.g. if you try to submit a change that is abandoned, this fails with `409 Conflict` because the state of the change doesn’t allow the submit operation.

`409 Conflict` is also used if you try to create a resource but the name is already occupied by an existing resource.

#### 412 Precondition Failed

`412 Precondition Failed` is used if a precondition from the request header fields is not fulfilled as described in the Preconditions section.

#### 422 Unprocessable Entity

`422 Unprocessable Entity` is returned if the ID of a resource that is specified in the request body cannot be resolved.

Part of Gerrit Code Review