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This extension comes with MediaWiki 1.35 and above. Thus you do not have to download it again. However, you still need to follow the other instructions provided.
MediaWiki extensions manual
Release status: stable
ImplementationTag, API
DescriptionAllows to store, retrieve and visualise information about templates
Author(s)Timo Tijhof, Moriel Schottlender, James Forrester, Trevor Pascal, Bartosz Dziewoński, Marielle Volz, ...
Latest version0.1.2 (Continuous updates)
Compatibility policySnapshots releases along with MediaWiki. Master is not backward compatible.
Database changesNo
LicenseGNU General Public License 2.0 or later
DownloadDownload extension
Git [?]:
  • $wgTemplateDataSuggestedValuesEditor
  • $wgTemplateDataUseGUI
Hooks used
Translate the TemplateData extension if it is available at translatewiki.net
Check usage and version matrix.
IssuesOpen tasks · Report a bug
The TemplateData extension introduces a
tag and an API which together allow editors to specify how templates should be invoked. This information is available as a nicely-formatted table for end-users, and as a JSON API, which enables other systems (e.g. VisualEditor) to build interfaces for working with templates and their parameters. See Help:TemplateData for in-depth help.
Editing data
The TemplateData extension works through having a
tag defined in the wikitext of a template page (optionally it can be transcluded from a different page as well). This is designed to be compatible with the common layout many wikis have of transcluding template documentation from a separate page (but is not required). This content of the
tag must be valid JSON using the format described below; note that all descriptions must be in plain text (no wikitext is accepted inside the template data).
When a
block is included on a page, the TemplateData extension performs the following checks when the page is being saved:
  1. The contents must be valid JSON;
  2. Each item within the JSON structure must be of the expected type as specified below (e.g. object, array, or a primitive); and
  3. For those items which have a specified list of possible values (e.g. params.yourParameterName.type​), the value in the JSON object must match one of those values.
If any of these checks fails, the server will not be permitted saving and an error message will be displayed above the edit page.
For autovalue items, bug 2700 prevents subst: from working in any template that is added inside a
, including
tags. The TemplateData block will save correctly, but the resulting wikitext will not be parsed correctly when the template is used.
Note that  you cannot use {{#tag:templatedata}} in lieu of
The below is a visualised version of the JSON data as defined on the template page enclosed by
tags. The formal specification is available in the TemplateData repository. Refer to Specification.md for the latest version.
TemplateData object
The TemplateData object is a JSON root element enclosed in a
element on the template page.
descriptionInterfaceText or nullA brief description of the template. It must be in plain text. Once filled, it can be displayed as caption when editing a single template and perhaps in search results when users pick one of many. The default is null.
paramsObject containing Param objectsAn object that maps each parameter name of the template to a corresponding Param object describing the properties of that parameter.
paramOrderArray containing parameter name stringsThe logical order in which parameters should be displayed. The array contains each parameter key exactly once. Each string must be a valid key in the params object.
setsArray containing
Set objects
An array containing set specifications. A set is a group of parameters that should be used together. The default is []. Note that the sets functionality is still in development.
formatstring, either inline or blockHow the template's wikitext representation SHOULD be laid out. The default is inline. See #Custom_formats for other custom formats.
mapsA Maps objectAn object that maps a simplified name of a third party consumer of the template data (i.e. Citoid, Special:MyLanguage/Wikidata​, etc.) to an object that in turn maps a name of a consumer parameter to one or more corresponding names of template parameters.
Param object
labelInterfaceTextnullA (very) brief name for the parameter. Try to keep under 20-ish characters.
descriptionInterfaceTextnullA brief description of the parameter, for users to know which to pick from an option list.
requiredbooleanfalseWhether the parameter is required for the template to work (true if this parameter must be specified).
suggestedbooleanfalseWhether the parameter is suggested for the template to be useful (true if this parameter should be specified).
deprecatedboolean or stringfalseWhether the parameter is deprecated. The value can be a string of instructions giving the user guidance what instead can be done, or be simply true.
aliasesArray containing strings[]List of aliases. An alias is an alternative name for the parameter that may be used instead of (not in addition to) the primary name. Aliases are not documented in a separate Parameter object. If they need more information, they should be in their own property marked "deprecated".
defaultInterfaceTextnullThe default value used by the template if no value is assigned to the parameter, or a description thereof.
autovaluestringnullA dynamically-generated default value in wikitext, such as today's date or the editing user's name; this will often involve wikitext substitution, such as {{subst:CURRENTYEAR}}​.
exampleInterfaceTextnullAn example text for the parameter, to help users fill in the proper value.
typestring"unknown"The type of the parameter, for (soft) type hinting. One of:
String ValueType of Parameter
"unknown"Assumed type if not set
"number"Any numerical value (without decimal points or thousand separators)
"string"Any textual value. May contain line breaks.
"line"Short text field – use for names, labels, and other short-form fields. This is supposed to be text that is not expected to contain line breaks.
"boolean"A boolean value ('1' for true, '0' for false, '' for unknown), see three-valued logic.
"date"A date in ISO 8601 format, e.g. "2014-05-09" or "2014-05-09T16:01:12Z"
"url"A URL, including protocol, e.g. "http://www.example.org", "https://example.org", or "//example.org".
"wiki-page-name"A valid MediaWiki page name for the current wiki. Doesn't have to exist, but if not, should be a valid page name which could be created.
"wiki-file-name"A valid MediaWiki file name for the current wiki. Doesn't have to exist, but if not, should be a valid file name which could be uploaded. Should not include the namespace (e.g. "Foo.svg" not "File:Foo.svg" or "Bild:Foo.svg").
"wiki-template-name"A valid MediaWiki Template name for the current wiki.
"wiki-user-name"A valid MediaWiki user name for the current wiki. Doesn't have to exist, but if not, should be a valid user name which could be created. Should not include the namespace (e.g. "Foo" not "User:Foo" or "Usario:Foo").
"content"Page content in wikitext, such as text style, links, images, etc.
"unbalanced-wikitext"Raw wikitext that should not be treated as standalone content because it is unbalanced – for example, templates concatenating incomplete wikitext as a bigger whole, such as {{echo|before=<u>|after=</u>}}
The name key of another parameter (must be a valid key in the params object). The current Parameter Object will inherit properties from the specified Parameter Object, with local properties overriding the inherited ones.
Set object
KeyObject or primitive typeDescription
labelInterfaceTextA (very) brief name for the parameter set. Try to keep under 20-ish characters.
paramsArray of stringsOne or more names of parameters to include in the set (each must be a valid key in the params object). A parameter may be in multiple sets. Not every parameter must be in a set.
Maps object
name of consumerobject{}An object that maps a name of a consumer to an object that in turn maps a name of a consumer parameter to one or more corresponding names of template parameters.
The names of the template parameters can be specified either as a string (one name), an array of strings (several names), or an array of arrays of strings (several sets of names); each of these strings must be a valid key in the params object elsewhere in the same template's TemplateData.
A specific template parameter may be in multiple maps, and it may be used in the values of multiple keys in a given map, but not every template parameter must be in a map.
A shortened example from English Wikipedia's Template:Cite_news#TemplateData illustrates the structure of a maps object.
{ "proveit": { "main": "title", "textarea": [ "quote" ] }, "citoid": { "title": "title", "url": "url", "publisher": "publisher", "publicationTitle": "work", "date": "date", "ISSN": [ "issn" ], "ISBN": [ "isbn" ], "contributor": "others", "author": [ [ "first", "last" ], [ "first2", "last2" ], [ "first9", "last9" ] ], "editor": [ [ "editor-first", "editor-last" ] ] } }
InterfaceText (string or object)
A free-form plain-text string (i.e. no wikitext or HTML) in the content-language of the wiki, or an object containing those strings keyed by language code.
The default value for all InterfaceText fields is null.
String type
If it is a string, it must contain a non-localized string in the content language of the local wiki.
Object type
If it is an object, the object must have this mapping:
Wikipedia language codestringLocalized string for use on the Wikipedia corresponding to the given language code.
Example of object mapping:
"en""Welcome to Wikipedia"
"de""Willkommen bei Wikipedia"
"fe""Bienvenue sur Wikipédia"
"nl""Welkom op Wikipedia"
"it""Benvenuti su Wikipedia"
"es""Bienvenidos a Wikipedia"
"ru""Добро пожаловать в Википедию"
An example TemplateData structure as specified within wikitext on a template page.
<templatedata>{ "description": "Label unsigned comments in a conversation.", "params": { "user": { "label": "User's name", "type": "wiki-user-name", "required": true, "description": "User name of person who forgot to sign their comment.", "aliases": ["1"] }, "date": { "label": "Date", "suggested": true, "description": { "en": "Timestamp of when the comment was posted, in YYYY-MM-DD format." }, "aliases": ["2"], "autovalue": "{{subst:#time:Y-m-d}}" }, "year": { "label": "Year", "type": "number" }, "month": { "label": "Month", "inherits": "year" }, "day": { "label": "Day", "inherits": "year" }, "comment": { "required": false } }, "sets": [ { "label": "Date", "params": ["year", "month", "day"] } ], "maps": { "ExampleConsumer": { "foo": "user", "bar": ["year", "month", "day"], "quux": [ "date", ["day", "month"], ["month", "year"], "year" ] } }}</templatedata>
Below is how the above example would be displayed on the template page:
Label unsigned comments in a conversation.
Template parameters
User's nameuser1User name of person who forgot to sign their comment.Userrequired
Timestamp of when the comment was posted, in YYYY-MM-DD format.
Auto value
Yearyearno descriptionNumberoptional
Monthmonthno descriptionNumberoptional
Daydayno descriptionNumberoptional
commentcommentno descriptionUnknownoptional
See the generated help at Special:ApiHelp/templatedata​. A sample invocation (formatted for human readability) is:

api.php​?​action=templatedata​&​titles=Template:Cite%20web​&​format=json [try in ApiSandbox]

This returns the template data for Template:Cite web. The
block for this template is on its transcluded template documentation page, en:Template:Cite web/doc.
Additions and changes to JSON as received from the API
The JSON structure provided in response to an API HTTP get request is significantly different than that which is defined in the
block. In response to the API request, extension TemplateData makes the following changes to the JSON object:
Visualised differences in a TemplateData JSON object delivered by the API
Wrapper objects added to JSON delivered by API
These are not defined in the JSON object enclosed by the
tags on the template page.
pagesPage ObjectThe Page object (contains one key which is the page number). If multiple pages were requested at one time there will be multiple Page Objects.

Page Object
(page number)
The TemplateData Object containing the information payload. The key is a static page number for the template page from which the JSON data was requested.

TemplateData Object (added by API)
The following key is added to the root of the JSON object which is enclosed in
tags on the template page.
titlestringThe page name of the template (e.g. "Template:Cite web").
This key is not contained in the JSON structure on the template page. It is added to the structure by the MediaWiki software in route to delivery via the API.
setsArray containing Set ObjectsAn array containing set specifications. A set is a group of parameters that should be used together.
If this does not exist on the template page it is added as an empty array to the structure provided by the API.

Parameter Objects from API
labelInterfaceTexttranslated to InterfaceText object, if not already in that format.
requiredbooleanIf not defined, default value of false added.
descriptionInterfaceText or nullIf defined as a string, converted to a InterfaceText object. If not defined, key is added with a null value.
deprecatedboolean or stringIf not defined, default value of false added.
aliasesArray of stringsIf not defined, a default empty array is assigned (i.e. [] ).
defaultstringIf not defined, default of "" is assigned.
typestringIf not defined, default of "unknown" is assigned.
inherits(removed)This key is removed and all inherited keys are added. Keys defined for the current parameter take precedence and any keys not defined on either the current param, or the one from which it inherits are given the default value.

InterfaceText (Object or null):
An object containing strings keyed by language code.
KeyObject or
primitive type
(containing localized strings by Wikipedia language code)
If a TemplateData field on the template page contains a string, not an object with localized strings, MediaWiki translates it into an InterfaceText Object with a string assigned to the key name of the source Wikipedia Wikipedia language code. The default for all InterfaceText fields is null.
(Wiki language code)stringLocalized string for use on the Wikipedia corresponding to the Wikipedia language code.
Example of JSON object provided by API
The response to an API request for the TemplateData structure in the Example section (above) can be seen:

Experimental dialog interface to edit templatedata JSON
See also
This extension is being used on one or more Wikimedia projects. This probably means that the extension is stable and works well enough to be used by such high-traffic websites. Look for this extension's name in Wikimedia's CommonSettings.php and InitialiseSettings.php configuration files to see where it's installed. A full list of the extensions installed on a particular wiki can be seen on the wiki's Special:Version page.
Last edited on 19 September 2021, at 11:17
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