Making big downloads resumable in Firefox

Firefox 28 and newer set network.http.response.timeout to 300 seconds by default, and that setting interferes with resuming large downloads and with overall stability of long transfers. Changing network.http.response.timeout in about:config to 0 (or a very large value) makes resumable downloads behave correctly and reduces failures, provided the server supports byte-range resumes. Firefox’s resume logic appears to rely on connection timeouts rather than the presence of .part files; with the default timeout Firefox can ignore existing .part files and fail to pick up an interrupted transfer. This behavior has been observed experimentally and echoes long-standing instability reports stretching back to at least 2005.

Practical options include adjusting the timeout in about:config or avoiding the browser’s downloader entirely by using wget -c -O "$filename" "$url", which reliably resumes and is more stable in the author’s tests. There are also manual .part-file workarounds but they are cumbersome. The failure mode may involve hidden retry logic tied to network.http.response.timeout, but no source-code confirmation was attempted. The writeup includes configuration steps and real-world testing notes aimed at users needing robust resumable downloads in Firefox.