title: " Gerrit Code Review - REST API" sidebar: restapi_sidebar permalink: rest-api.html

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.


Protocol Details


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) can authenticate with HTTP passwords by prefixing the endpoint URL with /a/. For example to authenticate to /projects/, request the URL /a/projects/. Gerrit will use HTTP basic authentication with the HTTP password from the user’s account settings page. This form of authentication bypasses the need for XSRF tokens.

An authorization cookie may be presented in the request URL inside the access_token query parameter. XSRF tokens are not required when a valid access_token is used in the URL.


Cross-site scripting may be supported if the administrator has configured site.allowOriginRegex.

Approved web applications running from an allowed origin can rely on CORS preflight to authorize requests requiring cookie based authentication, or mutations (POST, PUT, DELETE). Mutations require a valid XSRF token in the X-Gerrit-Auth request header.

Alternatively applications can use access_token in the URL (see above) to authorize requests. Mutations sent as POST with a request content type of text/plain can skip CORS preflight. Gerrit accepts additional query parameters $m to override the correct method (PUT, POST, DELETE) and $ct to specify the actual content type, such as application/json; charset=UTF-8. Example:

    POST /changes/42/topic?$m=PUT&$ct=application/json%3B%20charset%3DUTF-8&access_token=secret HTTP/1.1
        Content-Type: text/plain
        Content-Length: 23

        {"topic": "new-topic"}


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

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

By default most APIs return pretty-printed JSON, which uses extra whitespace to make the output more readable for humans.

Compact JSON can be requested by setting the pp=0 query parameter, or by setting the Accept HTTP request header to include application/json:

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

Producing (and parsing) the non-pretty compact format is more efficient, so tools should request it whenever possible.

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 ... ]

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.

Input Format

Unknown JSON parameters will simply be ignored by Gerrit without causing an exception. This also applies to case-sensitive parameters, such as map keys.


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


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

Response Codes

The Gerrit REST endpoints use HTTP status codes as described in the HTTP specification.

In most cases, the response body of an error response will be a plaintext, human-readable error message.

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

400 Bad Request

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

403 Forbidden

403 Forbidden” is returned if the operation is not allowed because the calling user does not have sufficient permissions.

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

403 Forbidden” is also returned 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 returned 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 returned 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 returned if you try to create a resource but the name is already occupied by an existing resource.

412 Precondition Failed

412 Precondition Failed” is returned 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