Resume a Firefox download // in a new session or on a different machineOften times you may have a partially completed download that gets interrupted - whether by Firefox crashing, your computer freezing, or a network interruption. In my case, I was downloading a very large file (>4gb) and found that, a couple hours into it, it was only halfway through. I wanted to pause the download and finish it on a different computer. After a bit of searching, here is a simple method to accomplish that in Firefox, without needing other download managers, etc.
1. Pause the download if you desire to continue it later. (This may already have been decided for you from a crash)
2. You will find two files in the download location: "filename.ext" and "filename.ext.part"
3. Start a new download of the file in a NEW location
4. Pause the download just after it begins - this allows Firefox to create a new file and .part file
5. Move your original (partially downloaded) files to this new location and OVERWRITE the new files
6. Then resume (unpause) the download in Firefox, and it jumps to the point of what you had previously downloaded!
Note that resuming a download depends on the capabilities of the server, though most can do it. Also, pausing a download will create a "clean" .part file, but if you complete a download using a .part file from a crash, etc, it may still be corrupted. Good luck!