Cloudflare will return gzip or brotli encoded responses to compatible clients / browsers for the following content-types:
If you do not want a particular response from your origin to be encoded, you can disable this by setting
cache-control: no-transform at your origin and turning Origin Cache Control -> On using a Page Rule.
How do I enable Brotli compression?
You can locate the setting for Brotli under the Speed section of your website's settings: