Making big downloads resumable in Firefox
Points and comments are a snapshot, not live.
Setting Firefox's network.http.response.timeout to 0 makes big downloads resumable.
Firefox 28+ sets network.http.response.timeout to 300 seconds, which blocks resume of large downloads. Setting it to 0 in about:config resolves the issue experimentally, though the author does not understand why. Resumable downloads in Firefox have been unstable since at least 2005. The author suggests wget -c as a non-Firefox workaround.
What commenters are saying
Many commenters note browsers have long been bad at large downloads, recommending external downloaders like aria2, JDownloader 2, and GetRight. Some describe a manual .part file shuffle to force resume. One commenter questions whether this is due to server changes during resume. A few express frustration that basic download management remains broken in Firefox for decades.