`<FORMAT>` is the desired [output file format](https://docs.scrapy.org/en/latest/topics/feed-exports.html#serialization-formats).

Possible values include: `csv`, `json`, `jsonlines`, `xml`. You can
also [implement support for more formats](https://docs.scrapy.org/en/latest/topics/exporters.html).

> [!WARNING]
> If you export in CSV format, and in your spider code you yield
> items as Python dictionaries, only the fields present on the first yielded
> item are exported for all items.
> 
> One solution is to [customize output fields](https://docs.scrapy.org/en/latest/topics/exporters.html#scrapy.exporters.BaseItemExporter.fields_to_export) through the `fields` [feed
> option](https://docs.scrapy.org/en/latest/topics/feed-exports.html#feed-options) of [FEEDS](https://docs.scrapy.org/en/latest/topics/feed-exports.html#feeds) or
> through the [FEED_EXPORT_FIELDS](https://docs.scrapy.org/en/latest/topics/feed-exports.html#feed-export-fields) Scrapy setting to explicitly indicate all
> fields to export.
> 
> You can alternatively yield something other than a Python dictionary that
> supports declaring all possible fields, such as an [Item object](https://docs.scrapy.org/en/latest/topics/items.html#item-objects) or an
> [attrs object](https://docs.scrapy.org/en/latest/topics/items.html#attr-s-objects).