Prefetching considered harmful

17 Mar 2025

I’ve been trying to get prefetching working in an app I’m building at the moment, but Firefox has been consistently ignoring my wishes and only fetching on click.

I looked in my about:config and, lo and behold, prefetching behaviour had been disabled. I didn’t remember doing that? I turned it back on but it still didn’t work. I checked about:config again, and it was disabled again. What??

To keep it short, uBlock Origin and Decentraleyes—I’m still not sure if I need both—each had a setting in them to disable prefetching behaviour. Apparently it’s harmful, privacy-wise, because it allows the browser to connect to resources that would’ve otherwise been blocked.

What now, then? I probably want to keep prefetching disabled because I think I value my privacy that much, which means there’s no point me implementing it. I’m going to look elsewhere for performance gains.