I'm still unconvinced about this addition. And I don't even dislike Zstandard.
The main motivation seems to be that while Zstandard is worse than Brotli at the highest level, it's substantially faster than Brotli when data has to be compressed on the fly with a limited computation budget. That might be true, but I'm yet to see any concrete or even anecdotal evidence even in the issue tracker [1] while there exist some benchmarks where both Zstandard and Brotli are fast enough for the web usage even at lower levels [2].
According to their FAQ [3] Meta and Akamai have successfully used Zstandard in their internal network, but my gut feeling is that they never actually tried to optimize Brotli instead (and I'd like to be proven wrong about this, because that would be a great information then!). In fact, Meta employs the main author of Zstandard so it would have been easier to tune Zstandard instead of Brotli. While Brotli has some fundamental difference from Zstandard---in particular Brotli doesn't use arithmetic-equivalent coding---, no one has concretely demonstrated that difference would prevent Brotli from being fast enough for dynamic contents in my opinion.
The main motivation seems to be that while Zstandard is worse than Brotli at the highest level, it's substantially faster than Brotli when data has to be compressed on the fly with a limited computation budget. That might be true, but I'm yet to see any concrete or even anecdotal evidence even in the issue tracker [1] while there exist some benchmarks where both Zstandard and Brotli are fast enough for the web usage even at lower levels [2].
According to their FAQ [3] Meta and Akamai have successfully used Zstandard in their internal network, but my gut feeling is that they never actually tried to optimize Brotli instead (and I'd like to be proven wrong about this, because that would be a great information then!). In fact, Meta employs the main author of Zstandard so it would have been easier to tune Zstandard instead of Brotli. While Brotli has some fundamental difference from Zstandard---in particular Brotli doesn't use arithmetic-equivalent coding---, no one has concretely demonstrated that difference would prevent Brotli from being fast enough for dynamic contents in my opinion.
[1] https://issues.chromium.org/issues/40196713
[2] https://github.com/powturbo/TurboBench/issues/43
[3] https://docs.google.com/document/d/14dbzMpsYPfkefAJos124uPrl...