JSON API¶

Datasette provides a JSON API for your SQLite databases. Anything you can do through the Datasette user interface can also be accessed as JSON via the API.

To access the API for a page, either click on the .json link on that page or edit the URL and add a .json extension to it.

If you started Datasette with the --cors option, each JSON endpoint will be served with the following additional HTTP headers:

Access-Control-Allow-Origin: *
Access-Control-Allow-Headers: Authorization
Access-Control-Expose-Headers: Link

This means JavaScript running on any domain will be able to make cross-origin requests to fetch the data.

If you start Datasette without the --cors option only JavaScript running on the same domain as Datasette will be able to access the API.

Different shapes¶

The default JSON representation of data from a SQLite table or custom query looks like this:

{
    "database": "sf-trees",
    "table": "qSpecies",
    "columns": [
        "id",
        "value"
    ],
    "rows": [
        [
            1,
            "Myoporum laetum :: Myoporum"
        ],
        [
            2,
            "Metrosideros excelsa :: New Zealand Xmas Tree"
        ],
        [
            3,
            "Pinus radiata :: Monterey Pine"
        ]
    ],
    "truncated": false,
    "next": "100",
    "next_url": "http://127.0.0.1:8001/sf-trees-02c8ef1/qSpecies.json?_next=100",
    "query_ms": 1.9571781158447266
}

The columns key lists the columns that are being returned, and the rows key then returns a list of lists, each one representing a row. The order of the values in each row corresponds to the columns.

The _shape parameter can be used to access alternative formats for the rows key which may be more convenient for your application. There are three options:

?_shape=arrays - "rows" is the default option, shown above
?_shape=objects - "rows" is a list of JSON key/value objects
?_shape=array - an JSON array of objects
?_shape=array&_nl=on - a newline-separated list of JSON objects
?_shape=arrayfirst - a flat JSON array containing just the first value from each row
?_shape=object - a JSON object keyed using the primary keys of the rows

_shape=objects looks like this:

{
    "database": "sf-trees",
    ...
    "rows": [
        {
            "id": 1,
            "value": "Myoporum laetum :: Myoporum"
        },
        {
            "id": 2,
            "value": "Metrosideros excelsa :: New Zealand Xmas Tree"
        },
        {
            "id": 3,
            "value": "Pinus radiata :: Monterey Pine"
        }
    ]
}

_shape=array looks like this:

[
    {
        "id": 1,
        "value": "Myoporum laetum :: Myoporum"
    },
    {
        "id": 2,
        "value": "Metrosideros excelsa :: New Zealand Xmas Tree"
    },
    {
        "id": 3,
        "value": "Pinus radiata :: Monterey Pine"
    }
]

_shape=array&_nl=on looks like this:

{"id": 1, "value": "Myoporum laetum :: Myoporum"}
{"id": 2, "value": "Metrosideros excelsa :: New Zealand Xmas Tree"}
{"id": 3, "value": "Pinus radiata :: Monterey Pine"}

_shape=arrayfirst looks like this:

[1, 2, 3]

_shape=object looks like this:

{
    "1": {
        "id": 1,
        "value": "Myoporum laetum :: Myoporum"
    },
    "2": {
        "id": 2,
        "value": "Metrosideros excelsa :: New Zealand Xmas Tree"
    },
    "3": {
        "id": 3,
        "value": "Pinus radiata :: Monterey Pine"
    }
]

The object shape is only available for queries against tables - custom SQL queries and views do not have an obvious primary key so cannot be returned using this format.

The object keys are always strings. If your table has a compound primary key, the object keys will be a comma-separated string.

Pagination¶

The default JSON representation includes a "next_url" key which can be used to access the next page of results. If that key is null or missing then it means you have reached the final page of results.

Other representations include pagination information in the link HTTP header. That header will look something like this:

link: <https://latest.datasette.io/fixtures/sortable.json?_next=d%2Cv>; rel="next"

Here is an example Python function built using requests that returns a list of all of the paginated items from one of these API endpoints:

def paginate(url):
    items = []
    while url:
        response = requests.get(url)
        try:
            url = response.links.get("next").get("url")
        except AttributeError:
            url = None
        items.extend(response.json())
    return items

Special JSON arguments¶

Every Datasette endpoint that can return JSON also accepts the following query string arguments:

?_shape=SHAPE

The shape of the JSON to return, documented above.

?_nl=on

When used with ?_shape=array produces newline-delimited JSON objects.

?_json=COLUMN1&_json=COLUMN2

If any of your SQLite columns contain JSON values, you can use one or more _json= parameters to request that those columns be returned as regular JSON. Without this argument those columns will be returned as JSON objects that have been double-encoded into a JSON string value.

Compare this query without the argument to this query using the argument

?_json_infinity=on

If your data contains infinity or -infinity values, Datasette will replace them with None when returning them as JSON. If you pass _json_infinity=1 Datasette will instead return them as Infinity or -Infinity which is invalid JSON but can be processed by some custom JSON parsers.

?_timelimit=MS

Sets a custom time limit for the query in ms. You can use this for optimistic queries where you would like Datasette to give up if the query takes too long, for example if you want to implement autocomplete search but only if it can be executed in less than 10ms.

?_ttl=SECONDS

For how many seconds should this response be cached by HTTP proxies? Use ?_ttl=0 to disable HTTP caching entirely for this request.

?_trace=1

Turns on tracing for this page: SQL queries executed during the request will be gathered and included in the response, either in a new "_traces" key for JSON responses or at the bottom of the page if the response is in HTML.

The structure of the data returned here should be considered highly unstable and very likely to change.

Only available if the trace_debug setting is enabled.

Table arguments¶

The Datasette table view takes a number of special query string arguments.

Column filter arguments¶

You can filter the data returned by the table based on column values using a query string argument.

?column__exact=value or ?_column=value

Returns rows where the specified column exactly matches the value.

?column__not=value

Returns rows where the column does not match the value.

?column__contains=value

Rows where the string column contains the specified value (column like "%value%" in SQL).

?column__endswith=value

Rows where the string column ends with the specified value (column like "%value" in SQL).

?column__startswith=value

Rows where the string column starts with the specified value (column like "value%" in SQL).

?column__gt=value

Rows which are greater than the specified value.

?column__gte=value

Rows which are greater than or equal to the specified value.

?column__lt=value

Rows which are less than the specified value.

?column__lte=value

Rows which are less than or equal to the specified value.

?column__like=value

Match rows with a LIKE clause, case insensitive and with % as the wildcard character.

?column__notlike=value

Match rows that do not match the provided LIKE clause.

?column__glob=value

Similar to LIKE but uses Unix wildcard syntax and is case sensitive.

?column__in=value1,value2,value3

Rows where column matches any of the provided values.

You can use a comma separated string, or you can use a JSON array.

The JSON array option is useful if one of your matching values itself contains a comma:

?column__in=["value","value,with,commas"]

?column__notin=value1,value2,value3

Rows where column does not match any of the provided values. The inverse of __in=. Also supports JSON arrays.

?column__arraycontains=value

Works against columns that contain JSON arrays - matches if any of the values in that array match the provided value.

This is only available if the json1 SQLite extension is enabled.

?column__arraynotcontains=value

Works against columns that contain JSON arrays - matches if none of the values in that array match the provided value.

This is only available if the json1 SQLite extension is enabled.

?column__date=value

Column is a datestamp occurring on the specified YYYY-MM-DD date, e.g. 2018-01-02.

?column__isnull=1

Matches rows where the column is null.

?column__notnull=1

Matches rows where the column is not null.

?column__isblank=1

Matches rows where the column is blank, meaning null or the empty string.

?column__notblank=1

Matches rows where the column is not blank.

Special table arguments¶

?_col=COLUMN1&_col=COLUMN2

List specific columns to display. These will be shown along with any primary keys.

?_nocol=COLUMN1&_nocol=COLUMN2

List specific columns to hide - any column not listed will be displayed. Primary keys cannot be hidden.

?_labels=on/off

Expand foreign key references for every possible column. See below.

?_label=COLUMN1&_label=COLUMN2

Expand foreign key references for one or more specified columns.

?_size=1000 or ?_size=max

Sets a custom page size. This cannot exceed the max_returned_rows limit passed to datasette serve. Use max to get max_returned_rows.

?_sort=COLUMN

Sorts the results by the specified column.

?_sort_desc=COLUMN

Sorts the results by the specified column in descending order.

?_search=keywords

For SQLite tables that have been configured for full-text search executes a search with the provided keywords.

?_search_COLUMN=keywords

Like _search= but allows you to specify the column to be searched, as opposed to searching all columns that have been indexed by FTS.

?_searchmode=raw

With this option, queries passed to ?_search= or ?_search_COLUMN= will not have special characters escaped. This means you can make use of the full set of advanced SQLite FTS syntax, though this could potentially result in errors if the wrong syntax is used.

?_where=SQL-fragment

If the execute-sql permission is enabled, this parameter can be used to pass one or more additional SQL fragments to be used in the WHERE clause of the SQL used to query the table.

This is particularly useful if you are building a JavaScript application that needs to do something creative but still wants the other conveniences provided by the table view (such as faceting) and hence would like not to have to construct a completely custom SQL query.

Some examples:

?_through={json}

This can be used to filter rows via a join against another table.

The JSON parameter must include three keys: table, column and value.

table must be a table that the current table is related to via a foreign key relationship.

column must be a column in that other table.

value is the value that you want to match against.

For example, to filter roadside_attractions to just show the attractions that have a characteristic of "museum", you would construct this JSON:

{
    "table": "roadside_attraction_characteristics",
    "column": "characteristic_id",
    "value": "1"
}

As a URL, that looks like this:

?_through={%22table%22:%22roadside_attraction_characteristics%22,%22column%22:%22characteristic_id%22,%22value%22:%221%22}

Here's an example.

?_next=TOKEN

Pagination by continuation token - pass the token that was returned in the "next" property by the previous page.

?_facet=column

Facet by column. Can be applied multiple times, see Facets. Only works on the default JSON output, not on any of the custom shapes.

?_facet_size=100

Increase the number of facet results returned for each facet. Use ?_facet_size=max for the maximum available size, determined by max_returned_rows.

?_nofacet=1

Disable all facets and facet suggestions for this page, including any defined by Facets in metadata.json.

?_nosuggest=1

Disable facet suggestions for this page.

?_nocount=1

Disable the select count(*) query used on this page - a count of None will be returned instead.

Expanding foreign key references¶

Datasette can detect foreign key relationships and resolve those references into labels. The HTML interface does this by default for every detected foreign key column - you can turn that off using ?_labels=off.

You can request foreign keys be expanded in JSON using the _labels=on or _label=COLUMN special query string parameters. Here's what an expanded row looks like:

[
    {
        "rowid": 1,
        "TreeID": 141565,
        "qLegalStatus": {
            "value": 1,
            "label": "Permitted Site"
        },
        "qSpecies": {
            "value": 1,
            "label": "Myoporum laetum :: Myoporum"
        },
        "qAddress": "501X Baker St",
        "SiteOrder": 1
    }
]

The column in the foreign key table that is used for the label can be specified in metadata.json - see Specifying the label column for a table.

Discovering the JSON for a page¶

Most of the HTML pages served by Datasette provide a mechanism for discovering their JSON equivalents using the HTML link mechanism.

You can find this near the top of the source code of those pages, looking like this:

<link rel="alternate"
  type="application/json+datasette"
  href="https://latest.datasette.io/fixtures/sortable.json">

The JSON URL is also made available in a Link HTTP header for the page:

Link: https://latest.datasette.io/fixtures/sortable.json; rel="alternate"; type="application/json+datasette"