The Accept-Encoding header sent by my browser is “gzip, deflate, br”. However, my origin server only receives the Accept-Encoding header as “gzip”. All the articles mention that the origin server should receive the request header as “br, gzip”.
For incoming requests, the value of this header will always be set to accept-encoding: br, gzip . If the client set a different value, such as accept-encding: deflate , it will be overwritten and the original value will be available in request.cf.clientAcceptEncoding .
I have already enabled the Brotli switch in the Speed > Optimization > Content Optimization tab.
And I performed the following tests:
Whether I used the command curl https://mysite -I -H "Accept-Encoding: gzip" or curl https://mysite -I -H "Accept-Encoding: br", I checked the Nginx logs on my origin server and found that the Accept-Encoding header sent by Cloudflare only contained “gzip”. And the response after my curl command is “br”.
However, if I disable the Brotli switch, I still receive only “gzip” in the Accept-Encoding header, and the response after the curl command is also “gzip”.
The above tests indicate that the Brotli switch is effective, but why am I only receiving “gzip” on my origin server? How can I receive “br”?
Yeah, that ticket was closed to soon, and somehow an answer with no solution has been chosen as the solution, with no possibility to object or anything.
However, as of a week or two ago, our origin started to receive both gzip and br. Maybe they roll it out gradually or something.
Enable Brotli:
client(browser) send request with “Accept-Encoding: br”
→ Cloudflare send request with “Accept-Encoding: gzip” // here is unexpected
→ Origin server receive request with “Accept-Encoding: gzip”
← Origin server return response with “content-encoding: gzip”
← Cloudflare return response with “content-encoding: br” // Enabling the Brotli is effective.
Disable Brotli:
client(browser) send request with “Accept-Encoding: gzip”
→ Cloudflare send request with “Accept-Encoding: gzip”
→ Origin server receive request with “Accept-Encoding: gzip”
← Origin server return response with “content-encoding: gzip”
← Cloudflare return response with “content-encoding: gzip” // Disabling the Brotli is effective.
I am seeing this behavior as well. Oddly enough, our origin had been getting "Accept-Encoding: br, gzip” for a period of time, but Cloudflare dropped br on 10/27.
I had opened a support ticket (#2993959) on 10/20 because I was not seeing evidence that the compression passthrough was happening. My impression was that Cloudflare was recompressing my origin’s br11 content with br4 on the fly.
On 11/1 I updated the original support ticket to ask about why br was dropped from the Accept-Encoding header to my origin. I haven’t gotten a response on the ticket yet, but I’ll try to update here when I do.
My suspicion is that this person had it right with their community comment elsewhere: End-to-end Brotli? - #5 by i40west. Things with Cloudflare’s brotli from origin don’t seem to be entirely working quite yet.