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# CSV export

Any Datasette table, view or custom SQL query can be exported as CSV.

To obtain the CSV representation of the table you are looking, click the "this data as CSV" link.

You can also use the advanced export form for more control over the resulting file, which looks like this and has the following options:

Advanced export form. You can get the data in different JSON shapes, and CSV options are download file, expand labels and stream all rows.

- download file - instead of displaying CSV in your browser, this forces your browser to download the CSV to your downloads directory.

- expand labels - if your table has any foreign key references this option will cause the CSV to gain additional `COLUMN_NAME_label` columns with a label for each foreign key derived from the linked table. In this example the `city_id` column is accompanied by a `city_id_label` column.

- stream all rows - by default CSV files only contain the first max_returned_rows records. This option will cause Datasette to loop through every matching record and return them as a single CSV file.

You can try that out on https://latest.datasette.io/fixtures/facetable?_size=4

## URL parameters

The following options can be used to customize the CSVs returned by Datasette.

`?_header=off`

  This removes the first row of the CSV file specifying the headings - only the row data will be returned.

`?_stream=on`

  Stream all matching records, not just the first page of results. See below.

`?_dl=on`

  Causes Datasette to return a `content-disposition: attachment; filename="filename.csv"` header.

## Streaming all records

The stream all rows option is designed to be as efficient as possible - under the hood it takes advantage of Python 3 asyncio capabilities and Datasette's efficient pagination to stream back the full CSV file.

Since databases can get pretty large, by default this option is capped at 100MB - if a table returns more than 100MB of data the last line of the CSV will be a truncation error message.

You can increase or remove this limit using the max_csv_mb config setting. You can also disable the CSV export feature entirely using allow_csv_stream.