API:Errors and warnings

This page is part of the MediaWiki Action API documentation.

If something goes wrong in an API request, an error or a warning will be thrown (although the HTTP response will usually still be 200 OK). Warnings are thrown for non-fatal conditions such as invalid parameters, whereas errors are only thrown for fatal conditions.

Warnings

Warnings are grouped by the name of the module that caused them. Multiple warnings from the same module are separated by a newline. In the legacy error formatting mode (see below), which is the default, warnings are output in the following format:

"warnings": {
    "modulename": {
      "*": "warning text"
    }
  }

(* will be replaced by warnings when formatversion=2 is used.)

When a non-legacy error formatting option is used, warnings are output in the same format as errors. E.g. with errorformat=wikitext the format will be:

"warnings": [
    {
        "code": "warning message key",
        "*": "text of warning",
        "module": "API module which caused the warning"
    }
]

(* will be replaced with text when formatversion=2 is used.)

Warning messages

Type	Description	Warning message(s)
Disabled submodule	The `action=query` submodule has been disabled in the wiki. To check if a module is available before invoking it, see How do I check if an API module is available? in the FAQ.	The submodulename module has been disabled.
Missing submodule	The `list`, `prop` or `meta` submodule is not present in the wiki, for example if it is implemented by an extension that isn't loaded.	Unrecognized value for parameter list=submodule.
Parameter validation	Warnings thrown when validating parameters of any API module. paramname is replaced by the name of the parameter.	Too many values supplied for parameter paramname: the limit is limit. Unrecognized value for parameter paramname: value. Unrecognized values for parameter paramname: value1, value2, value3

Errors

Error formats

Since MediaWiki 1.29 errors are localizable, and available in multiple formats. An error (or warning) is expected to consist of a message, an error code (an arbitrary string, usually generated from the message key; see also #Standard error messages below), and optional extra data (an associative array). An API response with errors will look like this:

{
    "errors": [
        {
            "code": "error-code",
            /* ...error message..., */
            "data": [ /* ...any extra data... */ ],
            "module": "path to the API module that generated the error"
        },
        /* ...more errors... */
    ],
    "docref": "human-readable message on where to find help"
}

The data key in the output above will be missing if there is no extra data to display.

The way the error message in the output above is returned to the client is controlled by the errorformat API parameter. The various error formats available are:

Format	Description	Output
html	Intended for human display in HTML-capable clients. MediaWiki will ensure that the HTML is safe; it is just as trustworthy as article content (both are parsed Wikitext).	"html": "the message, interpreted as wikitext and parsed into HTML"
wikitext		"text": "the message as-is, with parameter substitution but without any parsing"
plaintext	Intended for human display in HTML-incapable clients. Plaintext conversion is a minimal, best-effort transformation to make the message (assumed to contain wikitext) more readable: tags are removed, HTML entities are replaced, certain HTML tags are intelligently replaced with punctuation.	"text": "the message, like wikitext, but with added plaintext conversion"
raw	Intended as a machine-readable format (note that the error key is more unique than the error code). Parameters can themselves be objects with `key` and `params` fields.	"key": "message key", "params": [ /* ...message parameters... */ ]
none	No message information at all.
bc	The default, for backward compatibility. There’s no point in specifying this value, use one of the non-legacy formats instead.	See #Legacy format

For the formatting modes which involve message lookup (html, wikitext and plaintext) the API parameter errorlang can be used to set the language (only needed when different from the content language) and errorsuselocal to set whether the MediaWiki: namespace can be used to override default error messages.

Error codes are also returned in the MediaWiki-API-Error response HTTP header, separated by commas when there are multiple errors.

For an example error response or to test your client's error handling, visit https://en.wikipedia.org/w/api.php?action=blah&errorformat=plaintext&format=jsonfm&formatversion=2

API responses can contain multiple errors. For an example, try adding the lines the abusefilter will block this and the abusefilter will also block this to a Test Wikipedia page as API sandbox (if you are logged in, go to the action=edit tab and click Auto-fill the token first before making the request).

When errorformat is not set (or set to bc), errors will be displayed in the legacy format instead.

Legacy format

In the legacy error format, there is always at most one error; additional ones are discarded. The response looks like this:

{
    "error": {
        "code": "error-code",
        "info": "the message as-is, with parameter substitution but without any parsing",
        /* ...any extra data... */
    }
}

The extra data in the output above is spliced into the object instead of being under the data key.

Error messages in documentation

Error messages are documented in this wiki as shown below, which corresponds to the json error response in #Legacy format above:

Code	Info
errorcode	error message

The various error messages are:

Type	Description	Error message(s)
Type	Description	Code	Info
Disabled module	The action module has been disabled in the wiki. To check if a module is available before invoking it, see How do I check if an API module is available? in the FAQ.	moduledisabled	The modulename module has been disabled.
Missing module	The action module is not present in the wiki, for example if it is implemented by an extension that isn't loaded	unknown_action	Unrecognized value for parameter action: modulename.
Parameter validation	Errors thrown when validating parameters of any API module. paramname is replaced by the name of the parameter.	multival_paramname	Only one of 'value1', 'value2', 'value3' is allowed for parameter 'paramname'
		unknown_paramname	Unrecognized value for parameter `paramname`: value.
		paramname	`paramname` may not be less than min (set to value).
		paramname	`paramname` may not be over max (set to value) for bots or sysops.
		paramname	`paramname` may not be over max (set to value) for users.
		badtimestamp_paramname	Invalid value "value" for timestamp parameter `paramname`.
		baduser_paramname	Invalid value "value" for user parameter `paramname`.
		invalidparammix	The parameters param1, param2, param3 cannot be used together
		missingparam	One of the parameters param1, param2, param3 is required
		_badcontinue	Invalid continue param. You should pass the original value returned by the previous query

Standard error messages

Some generic error messages are shared among modules. If a module can throw these errors, that's explicitly mentioned in its Possible errors section.

Code	Info
unknownerror	Unknown error: This usually means something crazy like a rare race condition occurred. If you get this error, retry your request until it succeeds or returns a more informative error message
unknownerror	Unknown error: "errorcode".
unknownerror-nocode	Unknown error.
unsupportednamespace	Pages in the Special namespace can't be edited
protectednamespace-interface	You're not allowed to edit interface messages
protectednamespace	You're not allowed to edit pages in the "namespace" namespace
customcssjsprotected	You're not allowed to edit custom CSS and JavaScript pages
cascadeprotected	This page is fully protected because it is included in the following pages, which are fully protected with the "cascading" option turned on: list of cascade-protected pages
protectedpage	The "right" right is required to edit this page
permissiondenied	Permission denied.
confirmemail	You must confirm your email address before editing pages. Please set and validate your email address through your user preferences.
blocked	You have been blocked from editing
autoblocked	Your IP address has been blocked automatically, because it was used by a blocked user
ratelimited	You've exceeded your rate limit. Please wait some time and try again
readonly	The wiki is currently in read-only mode
badtoken	Invalid token (did you remember to urlencode it?)
missingtitle	The page you requested doesn't exist
mustbeposted	Type of your HTTP request message must be POST
hookaborted	The modification you tried to make was aborted by an extension hook
nosuchpageid	There is no page with ID id
nosuchrevid	There is no revision with ID id
nosuchrcid	There is no change with rcid "id"
nosuchuser	The user you specified doesn't exist
invalidtitle	Bad title "title"
invaliduser	Invalid username "username"
assertbotfailed	"assert=bot" has been used, but logged in user is not a bot
assertuserfailed	"assert=user" has been used, but user is not logged in
readapidenied	You need read permission to use this module
noapiwrite	Editing of this wiki through the API is disabled. Make sure the `$wgEnableWriteAPI=true;` statement is included in the wiki's LocalSettings.php file

Additional notes

All error and warning outputs above use format=json&formatversion=2. For formatversion=1, the field docref will be replaced by *.

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