Toggl slow down over HTTP3

Tech Discussions
1

Hi Toggl team,

Great product as always! Thank you.

Since approximately Monday July 6, the Track web app (focus.toggl.com) became nearly unusable for me on some machines: multi-second click response, “this page is slowing down your browser” warnings, tab pinning a CPU core, and consoles full of interrupted connections to wss://focus.toggl.com/websockets and failed requests to api.plan.toggl.com (status null).

I traced the root cause: disabling HTTP/3 in the browser (Firefox: network.http.http3.enable = false) instantly restores normal performance. Plain TCP connections to your hosts (curl) always worked, with valid certificates. So the failure mode is: browsers negotiate HTTP/3 over QUIC (UDP 443) to your Google Cloud frontends, something on the network path mangles that UDP traffic mid-connection rather than rejecting it cleanly, and browsers hang/retry instead of falling back to TCP.

My question: did you enable or expand HTTP/3 / QUIC advertisement (Alt-Svc) on your load balancers around that date? A server-side rollout would exactly explain a sudden onset for users behind networks or security stacks that mishandle QUIC — a fairly common enterprise configuration.

Maybe this is a one-off from my setup or location; or else it might explain any other “app suddenly slow” complaints you are receiving this week. The client-side workaround (disable HTTP/3) is effective, and affected users’ network admins can fix it properly by making their QUIC blocking reject handshakes cleanly, which restores instant TCP fallback.

While investigating, I also noticed that crisp chat service was inducing a 2-3 second page-load latency, so I have blocked it and regained additional performance! Perhaps a setting to turn chat on and off would be useful; just a thought.

Happy to provide HAR captures, console logs, or timestamps if useful.

Browsers affected: Firefox-based (Zen, Firefox, Edge), Linux and Windows

2

Thanks for the detailed write-up and for doing such thorough investigation on this - that is genuinely useful information.

To answer your direct question: we do not have visibility into infrastructure-level changes like HTTP/3 or QUIC advertisement settings through this community forum, so we cannot confirm whether a server-side rollout happened around July 6. That said, your analysis is well-reasoned and the workaround you found (disabling HTTP/3 in the browser) is a practical step others in similar situations can try if they are seeing the same symptoms.

For anyone else reading this thread who is experiencing slowness with the Toggl Track web app, it is worth trying: in Firefox, setting network.http.http3.enable to false in about:config to see if performance improves. If it does, the issue is likely related to how QUIC/UDP traffic is being handled on your network path.

Regarding the Crisp chat latency you noticed, a toggle to disable the chat widget is not currently available in Toggl Track, but that is a reasonable idea and I will pass it along to the product team.

Thanks again for sharing such a clear breakdown - the level of detail here, including the browser versions, OS, and the specific failure pattern, is exactly the kind of thing that helps narrow down issues like this.

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