Please, can compression priority be specified

[sunnie-star]

May I ask if the compression priority of zstd and brotli can be specified when nginx adds third-party modules zstd and brotli? Is it determined based on the module order in ngx_module. c. But I tried to modify the order of add_madule during compilation, but the order in ngx_module. c always remains the same:
"ngx_http_brotli_filter_module",
"ngx_http_zstd_filter_module",
When the header of the request is "Accept-Encoding:br,zstd"， The compression priority displayed is zstd>br

However, the order of static modules will change according to the order of add_module, for example - add-module=.../ngx_http_zstd_module - add-module=.../ngx_brotli, in ngx_module. c:
"ngx_http_zstd_static_module",
"ngx_http_brotli_static_module"，

--add-module=.../ngx_brotli --add-module=.../ngx_http_zstd_module:
"ngx_http_brotli_static_module"，
"ngx_http_zstd_static_module",
But when the header of the request is “Accept Encoding: br, zstd”, the priority of returning static files is always br, regardless of the order of static_module in ngx_module

[angelomandato]

If you flip the Accept Encoding ordering, does it accept the first in the list? e.g.

Accept Encoding: zstd, br

I thought the order from the browser making the request sets this order and if there are matches, the first one in the list is used?

I found a site that said the the client implies a higher preference for gzip than for deflate when the ordering does not include q= values.

Accept-Encoding: gzip, deflate

But this is obviously not the case today, Chrome sets the order to "gzip, deflate, br, zstd", the exact opposite order that we are looking for.

In my mind it should be up to the web server if no q= parameters are specified.

I reviewed the RFCs 2616 and 7694, though 2616 and others will say the first value takes precedence for other types of fields, it does not say this specifically for encodings. Worse yet Accept-Encodings q= option (I don't think any clients use to indicate the ideal encoding choice) brings up more questions than answers. For example, this is what Chrome should be including in their header if they specified the q= values:

Accept-Encoding: zstd;q=1.0, br;q=0.9, deflate;q=0.3, gzip;q=0.2, *;q=0.1

I wonder if Nginx or Apache even interpret the q value, a discussion for another day.

My suggestion is to create a variable map in nginx to turn Brotli off except when the browser user agent is Safari for MAC, Safari for iOS, and WebView on iOS.