Metadata

Data loves metadata. Any time you run Datasette you can optionally include a JSON file with metadata about your databases and tables. Datasette will then display that information in the web UI.

Run Datasette like this:

datasette database1.db database2.db --metadata metadata.json

Your metadata.json file can look something like this:

{
    "title": "Custom title for your index page",
    "description": "Some description text can go here",
    "license": "ODbL",
    "license_url": "https://opendatacommons.org/licenses/odbl/",
    "source": "Original Data Source",
    "source_url": "http://example.com/"
}

The above metadata will be displayed on the index page of your Datasette-powered site. The source and license information will also be included in the footer of every page served by Datasette.

Any special HTML characters in description will be escaped. If you want to include HTML in your description, you can use a description_html property instead.

Per-database and per-table metadata

Metadata at the top level of the JSON will be shown on the index page and in the footer on every page of the site. The license and source is expected to apply to all of your data.

You can also provide metadata at the per-database or per-table level, like this:

{
    "databases": {
        "database1": {
            "source": "Alternative source",
            "source_url": "http://example.com/",
            "tables": {
                "example_table": {
                    "description_html": "Custom <em>table</em> description",
                    "license": "CC BY 3.0 US",
                    "license_url": "https://creativecommons.org/licenses/by/3.0/us/"
                }
            }
        }
    }
}

Each of the top-level metadata fields can be used at the database and table level.

Specifying units for a column

Datasette supports attaching units to a column, which will be used when displaying values from that column. SI prefixes will be used where appropriate.

Column units are configured in the metadata like so:

{
    "databases": {
        "database1": {
            "tables": {
                "example_table": {
                    "units": {
                        "column1": "metres",
                        "column2": "Hz"
                    }
                }
            }
        }
    }
}

Units are interpreted using Pint, and you can see the full list of available units in Pint’s unit registry. You can also add custom units to the metadata, which will be registered with Pint:

{
    "custom_units": [
        "decibel = [] = dB"
    ]
}

Setting which columns can be used for sorting

Datasette allows any column to be used for sorting by default. If you need to control which columns are available for sorting you can do so using the optional sortable_columns key:

{
    "databases": {
        "database1": {
            "tables": {
                "example_table": {
                    "sortable_columns": [
                        "height",
                        "weight"
                    ]
                }
            }
        }
    }
}

This will restrict sorting of example_table to just the height and weight columns.

You can also disable sorting entirely by setting "sortable_columns": []

By default, database views in Datasette do not support sorting. You can use sortable_columns to enable specific sort orders for a view called name_of_view in the database my_database like so:

{
“databases”: {
“my_database”: {
“tables”: {
“name_of_view”: {
“sortable_columns”: [
“clicks”, “impressions”

]

}

}

}

}

}

Specifying the label column for a table

Datasette’s HTML interface attempts to display foreign key references as labelled hyperlinks. By default, it looks for referenced tables that only have two columns: a primary key column and one other. It assumes that the second column should be used as the link label.

If your table has more than two columns you can specify which column should be used for the link label with the label_column property:

{
    "databases": {
        "database1": {
            "tables": {
                "example_table": {
                    "label_column": "title"
                }
            }
        }
    }
}

Hiding tables

You can hide tables from the database listing view (in the same way that FTS and Spatialite tables are automatically hidden) using "hidden": true:

{
    "databases": {
        "database1": {
            "tables": {
                "example_table": {
                    "hidden": true
                }
            }
        }
    }
}

Generating a metadata skeleton

Tracking down the names of all of your databases and tables and formatting them as JSON can be a little tedious, so Datasette provides a tool to help you generate a “skeleton” JSON file:

datasette skeleton database1.db database2.db

This will create a metadata.json file looking something like this:

{
    "title": null,
    "description": null,
    "description_html": null,
    "license": null,
    "license_url": null,
    "source": null,
    "source_url": null,
    "databases": {
        "database1": {
            "title": null,
            "description": null,
            "description_html": null,
            "license": null,
            "license_url": null,
            "source": null,
            "source_url": null,
            "queries": {},
            "tables": {
                "example_table": {
                    "title": null,
                    "description": null,
                    "description_html": null,
                    "license": null,
                    "license_url": null,
                    "source": null,
                    "source_url": null,
                    "units": {}
                }
            }
        },
        "database2": ...
    }
}

You can replace any of the null values with a JSON string to populate that piece of metadata.