This describes the details of the requests and responses you can expect from the addons.mozilla.org API.


All requests should be made with the header:

Content-type: application/json


Status Codes

There are some common API responses that you can expect to receive at times.

GET /api/v3/...
Status Codes:
  • 200 OK – Success.
  • 201 Created – Creation successful.
  • 202 Accepted – The request has been accepted for processing. This usually means one or more asyncronous tasks is being executed in the background so results aren’t immediately visible.
  • 204 No Content – Success (no content is returned).
  • 400 Bad Request – There was a problem with the parameters sent with this request.
  • 401 Unauthorized – Authentication is required or failed.
  • 403 Forbidden – You are not permitted to perform this action.
  • 404 Not Found – The requested resource could not be found.
  • 500 Internal Server Error – An unknown error occurred.
  • 503 Service Unavailable – The site is in maintenance mode at this current time and the operation can not be performed.

Bad Requests

When returning a HTTP 400 Bad Request response, the API will try to return some information about the error(s) in the body of the response, as a JSON object. The keys of that object indicate the field(s) that caused an error, and for each, a list of messages will be provided (often only one message will be present, but sometimes more). If the error is not attached to a specific field the key non_field_errors will be used instead.


    "username": ["This field is required."],
    "non_field_errors": ["Error not linked to a specific field."]

Unauthorized and Permission Denied

When returning HTTP 401 Unauthorized and HTTP 403 Permission Denied responses, the API will try to return some information about the error in the body of the response, as a JSON object. A detail property will contain a message explaining the error. In addition, in some cases, an optional code property will be present and will contain a constant corresponding to specific problems to help clients address the situation programmatically. The constants are as follows:

Value Description
ERROR_INVALID_HEADER The Authorization header is invalid.
ERROR_SIGNATURE_EXPIRED The signature of the token indicates it has expired.
ERROR_DECODING_SIGNATURE The token was impossible to decode and probably invalid.

Translated Fields

Fields that can be translated by users (typically name, description) have a special behaviour. The default is to return them as an object, with languages as keys and translations as values:

    "name": {
        "en-US": "Games",
        "fr": "Jeux",
        "kn": "ಆಟಗಳು"

However, for performance, if you pass the lang parameter to a GET request, then only the most relevant translation (the specified language or the fallback, depending on whether a translation is available in the requested language) will be returned as a string.

    "name": "Games"

This behaviour also applies to POST, PATCH and PUT requests: you can either submit an object containing several translations, or just a string. If only a string is supplied, it will only be used to translate the field in the current language.

Cross Origin

All APIs are available with Cross-Origin Resource Sharing unless otherwise specified.