Danbooru thumbnail images load slower with HTTP/2 compared to HTTP/1.1

Post by **jobbautista9** » 2025-08-03, 07:52

Operating system: Windows 11 x64
Browser version: 33.8.1.1
32-bit or 64-bit browser?: 64-bit
Problem URL: https://safebooru.donmai.us/posts?page= ... ancolle%29 (example, best reproduced with a logged-in account with the thumbnails per page set to 100 in settings)
Browser theme (if not default): Default
Installed add-ons: None
Installed plugins: (about:plugins): Flash, Silverlight, VLC

If possible, please include the output of help->troubleshooting information (as text):

I've noticed that whenever I searching through tags in Danbooru, the thumbnails of image results load one-at-a-time. It's so bad that it seems to hog my whole network connection, because I can't load anything else while the results page have not completely finished loading. So I investigated with a fresh profile (which is what the troubleshooting info above points to) and I eventually found out that HTTP/2 could be an issue. Toggling network.http.spdy.enabled.http2 to false (and restarting the browser to ensure Danbooru will only use HTTP/1.1) will make the site serve a Cloudflare captcha challenge at first (at least for me, but I never get the captcha with HTTP/2, and the Cloudflare cookie doesn't last long so I can't just force switch to HTTP/1 and call it a day), but after solving it the images now load a lot faster and in parallel instead of being a sequential one-at-a-time.

I tested as well in a Firefox 128-based browser and it seems there is no difference in loading speed whether HTTP1.1, HTTP2, or HTTP3 is used. Perhaps we should check out whether there are improvements in the HTTP/2 of current Mozilla code we can backport?

Lecco · Post by **Lecco** » 2025-08-16, 13:32

Believe it or not, setting network.http.spdy.enabled.http2 to false has solved the problem I was having since I had to switch to the SSE build.

First few pages would load at the usual speed, but as the time passed, the websites would load really slow or sometimes would not load completely.
During page load, the browser would often use 100% of one or two CPU cores.
Using the Developer Tools, I noticed that in the Network / Timings tab, the requests spent a ridiculous amount of time in the blocked state. (seconds, or sometimes 10s of seconds)
I had to restart the browser a few times per day because at one point, it would get virtually unusable for anything but generating fan noise.

After toggling the pref, I'm back to the usual speed I'm used to. Currently a tiny fraction of requests get blocked, but only in double digit miliseconds, which is probably normal.
A real headscratcher what could have caused this, since I did not change any settings before or after I switched to the SSE build.
I started changing settings only after I noticed the slower loading times and higher CPU temperatures than usual.

So thank you for the tip !

Post by **jobbautista9** » 2025-11-02, 11:56

Btw for those who want to force HTTP/1.1 on all sites while not making browsing Danbooru a CAPTCHA hell, I found out in this forum topic I made later that you won't get the Cloudflare CAPTCHAs when you apply a site-specific user-agent override (SSUAO) that doesn't contain Mozilla/5.0 in it. For general.useragent.override.donmai.us I use PaleMoon/33.9.1 Goanna/20251016 (%OS_SLICE% rv:6.8).

Pale Moon forum

Danbooru thumbnail images load slower with HTTP/2 compared to HTTP/1.1

Danbooru thumbnail images load slower with HTTP/2 compared to HTTP/1.1

Re: Danbooru thumbnail images load slower with HTTP/2 compared to HTTP/1.1

Re: Danbooru thumbnail images load slower with HTTP/2 compared to HTTP/1.1