wagtail/docs/advanced_topics/api/v2/usage.rst

==========================
Wagtail API v2 Usage Guide
==========================

The Wagtail API module exposes a public, read only, JSON-formatted API which
can be used by external clients (such as a mobile app) or the site's frontend.

This document is intended for developers using the API exposed by Wagtail. For
documentation on how to enable the API module in your Wagtail site, see
:doc:`/advanced_topics/api/v2/configuration`

.. contents::

Fetching content
================

To fetch content over the API, perform a ``GET`` request against one of the
following endpoints:

 - Pages ``/api/v2/pages/``
 - Images ``/api/v2/images/``
 - Documents ``/api/v2/documents/``

.. note::

    The available endpoints and their URLs may vary from site to site, depending
    on how the API has been configured.

Example response
----------------

Each response contains the list of items (``items``) and the total count
(``meta.total_count``). The total count is irrespective of pagination.

.. code-block:: text

    GET /api/v2/endpoint_name/

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": "total number of results"
        },
        "items": [
            {
                "id": 1,
                "meta": {
                    "type": "app_name.ModelName",
                    "detail_url": "http://api.example.com/api/v2/endpoint_name/1/"
                },
                "field": "value"
            },
            {
                "id": 2,
                "meta": {
                    "type": "app_name.ModelName",
                    "detail_url": "http://api.example.com/api/v2/endpoint_name/2/"
                },
                "field": "different value"
            }
        ]
    }

.. _apiv2_custom_page_fields:

Custom page fields in the API
-----------------------------

Wagtail sites contain many page types, each with their own set of fields. The
``pages`` endpoint will only expose the common fields by default (such as
``title`` and ``slug``).

To access custom page fields with the API, select the page type with the
``?type`` parameter. This will filter the results to only include pages of that
type but will also make all the exported custom fields for that type available
in the API.

For example, to access the ``published_date``, ``body`` and ``authors`` fields
on the ``blog.BlogPage`` model in the :ref:`configuration docs <apiv2_page_fields_configuration>`:

.. code-block:: text

    GET /api/v2/pages/?type=blog.BlogPage&fields=published_date,body,authors(name)

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": 10
        },
        "items": [
            {
                "id": 1,
                "meta": {
                    "type": "blog.BlogPage",
                    "detail_url": "http://api.example.com/api/v2/pages/1/",
                    "html_url": "http://www.example.com/blog/my-blog-post/",
                    "slug": "my-blog-post",
                    "first_published_at": "2016-08-30T16:52:00Z"
                },
                "title": "Test blog post",
                "published_date": "2016-08-30",
                "authors": [
                    {
                        "id": 1,
                        "meta": {
                            "type": "blog.BlogPageAuthor",
                        },
                        "name": "Karl Hobley"
                    }
                ]
            },

            ...
        ]
    }

.. note::

    Only fields that have been explicitly exported by the developer may be used
    in the API. This is done by adding a ``api_fields`` attribute to the page
    model. You can read about configuration :ref:`here <apiv2_page_fields_configuration>`.

This doesn't apply to images/documents as there is only one model exposed in
those endpoints. But for projects that have customised image/document models,
the ``api_fields`` attribute can be used to export any custom fields into the
API.

Pagination
----------

The number of items in the response can be changed by using the ``?limit``
parameter (default: 20) and the number of items to skip can be changed by using
the ``?offset`` parameter.

For example:

.. code-block:: text

    GET /api/v2/pages/?offset=20&limit=20

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": 50
        },
        "items": [
            pages 20 - 40 will be listed here.
        ]
    }

.. note::

    There may be a maximum value for the ``?limit`` parameter. This can be
    modified in your project settings by setting ``WAGTAILAPI_LIMIT_MAX`` to
    either a number (the new maximum value) or ``None`` (which disables maximum
    value check).

Ordering
--------

The results can be ordered by any field by setting the ``?order`` parameter to
the name of the field to order by.

.. code-block:: text

    GET /api/v2/pages/?order=title

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": 50
        },
        "items": [
            pages will be listed here in ascending title order (a-z)
        ]
    }

The results will be ordered in ascending order by default. This can be changed
to descending order by prefixing the field name with a ``-`` sign.

.. code-block:: text

    GET /api/v2/pages/?order=-title

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": 50
        },
        "items": [
            pages will be listed here in descending title order (z-a)
        ]
    }

.. note::

    Ordering is case-sensitive so lowercase letters are always ordered after
    uppercase letters when in ascending order.

Random ordering
^^^^^^^^^^^^^^^

Passing ``random`` into the ``?order`` parameter will make results return in a
random order. If there is no caching, each request will return results in a
different order.

.. code-block:: text

    GET /api/v2/pages/?order=random

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": 50
        },
        "items": [
            pages will be listed here in random order
        ]
    }

.. note::

    It's not possible to use ``?offset`` while ordering randomly because
    consistent random ordering cannot be guaranteed over multiple requests
    (so requests for subsequent pages may return results that also appeared in
    previous pages).

Filtering
---------

Any field may be used in an exact match filter. Use the filter name as the
parameter and the value to match against.

For example, to find a page with the slug "about":

.. code-block:: text

    GET /api/v2/pages/?slug=about

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": 1
        },
        "items": [
            {
                "id": 10,
                "meta": {
                    "type": "standard.StandardPage",
                    "detail_url": "http://api.example.com/api/v2/pages/10/",
                    "html_url": "http://www.example.com/about/",
                    "slug": "about",
                    "first_published_at": "2016-08-30T16:52:00Z"
                },
                "title": "About"
            },
        ]
    }

Filtering by tree position (pages only)
---------------------------------------

Pages can additionally be filtered by their position of the tree. For this,
there are two parameters you can use: ``?child_of`` and ``?descendant_of``.

The ``?child_of`` filter takes the id of a page and filters the list of results
to contain only direct children of that page.

For example, this can be useful for constructing the main menu, by passing the
id of the homepage to the filter:

.. code-block:: text

    GET /api/v2/pages/?child_of=2&show_in_menus=true

    HTTP 200 OK
    Content-Type: application/json

    {
        "meta": {
            "total_count": 5
        },
        "items": [
            {
                "id": 3,
                "meta": {
                    "type": "blog.BlogIndexPage",
                    "detail_url": "http://api.example.com/api/v2/pages/3/",
                    "html_url": "http://www.example.com/blog/",
                    "slug": "blog",
                    "first_published_at": "2016-09-21T13:54:00Z"
                },
                "title": "About"
            },
            {
                "id": 10,
                "meta": {
                    "type": "standard.StandardPage",
                    "detail_url": "http://api.example.com/api/v2/pages/10/",
                    "html_url": "http://www.example.com/about/",
                    "slug": "about",
                    "first_published_at": "2016-08-30T16:52:00Z"
                },
                "title": "About"
            },

            ...
        ]
    }

The ``?descendant_of`` filter also takes the id of a page but includes all
descendants (children of children) instead of just directly children.

Search
------

Passing a query to the ``?search`` parameter will perform a full-text search on
the results.

The query is split into "terms" (by word boundary), then each term is normalised
(lowercased and unaccented).

For example: ``?search=James+Joyce``

Search operator
^^^^^^^^^^^^^^^

The ``search_operator`` specifies how multiple terms in the query should be
handled. There are two possible values:

 - ``and`` - All terms in the search query (excluding stop words) must exist in
   each result
 - ``or`` - At least one term in the search query must exist in each result

The ``or`` operator is generally better than ``and`` as it allows the user to be
inexact with their query and the ranking algorithm will make sure that
irrelevant results are not returned at the top of the page.

The default search operator depends on whether the search engine being used by
the site supports ranking. If it does (Elasticsearch), the operator will default
to ``or``. Otherwise (database), it will default to ``and``.

For the same reason, it's also recommended to use the ``and`` operator when
using ``?search`` in conjunction with ``?order`` (as this disables ranking).

For example: ``?search=James+Joyce&order=-first_published_at&search_operator=and``

Fields
------

By default, only a subset of the available fields are returned in the response.
The ``?fields`` parameter can be used to both add additional fields to the
response and remove default fields that you know you won't need.

Additional fields
^^^^^^^^^^^^^^^^^

Additional fields can be added to the response by setting ``?fields`` to a
comma-separated list of field names you want to add.

For example, ``?fields=body,feed_image`` will add the ``body`` and ``feed_image``
fields to the response.

This can also be used across relationships. For example,
``?fields=body,feed_image(width,height)`` will nest the ``width`` and ``height``
of the image in the response.

All fields
^^^^^^^^^^

Setting ``?fields`` to an asterisk (``*``) will add all available fields to the
response. This is useful for discovering what fields have been exported.

For example: ``?fields=*``

Removing fields
^^^^^^^^^^^^^^^

Fields you know that you do not need can be removed by prefixing the name with a
``-`` and adding it to ``?fields``.

For example, ``?fields=-title,body`` will remove ``title`` and add ``body``.

This can also be used with the asterisk. For example, ``?fields=*,-body``
adds all fields except for ``body``.

Removing all default fields
^^^^^^^^^^^^^^^^^^^^^^^^^^^

To specify exactly the fields you need, you can set the first item in fields to
an underscore (``_``) which removes all default fields.

For example, ``?fields=_,title`` will only return the title field.

Detail views
------------

You can retrieve a single object from the API by appending its id to the end of
the URL. For example:

- Pages ``/api/v2/pages/1/``
- Images ``/api/v2/images/1/``
- Documents ``/api/v2/documents/1/``

All exported fields will be returned in the response by default. You can use the
``?fields`` parameter to customise which fields are shown.

For example: ``/api/v2/pages/1/?fields=_,title,body`` will return just the
``title`` and ``body`` of the page with the id of 1.

Default endpoint fields
=======================

Common fields
-------------

These fields are returned by every endpoint.

.. glossary::

    ``id``  (number)

        The unique ID of the object

        .. note::

            Except for page types, every other content type has its own id space
            so you must combine this with the ``type`` field in order to get a
            unique identifier for an object.

    ``type`` (string)

        The type of the object in ``app_label.ModelName`` format

    ``detail_url``  (string)

        The URL of the detail view for the object

Pages
-----

.. glossary::

    ``title``  (string)
    ``meta.slug``  (string)
    ``meta.show_in_menus``  (boolean)
    ``meta.seo_title``  (string)
    ``meta.search_description``  (string)
    ``meta.first_published_at``  (date/time)

        These values are taken from their corresponding fields on the page

    ``meta.html_url``  (string)

        If the site has an HTML frontend that's generated by Wagtail, this
        field will be set to the URL of this page

    ``meta.parent``

        Nests some information about the parent page (only available on detail
        views)

Images
------

.. glossary::

    ``title``  (string)

        The value of the image's title field. Within Wagtail, this is used in
        the image's ``alt`` HTML attribute.

    ``width``  (number)
    ``height``  (number)

        The size of the original image file

    ``meta.tags``  (list of strings)

        A list of tags associated with the image

Documents
---------

.. glossary::

    ``title``  (string)

        The value of the document's title field

    ``meta.tags``  (list of strings)

        A list of tags associated with the document

    ``meta.download_url``  (string)

        A URL to the document file

Changes since v1
================

Breaking changes
----------------

 - The results list in listing responses has been renamed to ``items`` (was
   previously either ``pages``, ``images`` or ``documents``)

Major features
--------------

 - The ``fields`` parameter has been improved to allow removing fields, adding
   all fields and customising nested fields

Minor features
--------------

 - ``html_url``, ``slug``, ``first_publised_at``, ``expires_at`` and
   ``show_in_menus`` fields have been added to the pages endpoint
 - ``download_url`` field has been added to the documents endpoint
 - Multiple page types can be specified in ``type`` parameter on pages endpoint
 - ``true`` and ``false`` may now be used when filtering boolean fields
 - ``order`` can now be used in conjunction with ``search``
 - ``search_operator`` parameter was added