While it's simple enough to bookmark your favourite Twitch streams or saved clips, sometimes you might have the need to store your own digital copy. A number of tools exist for downloading "vods" from Twitch, but Twitch Leecher is definitely one of the smarter choices.
As the utility's GitHub description explains, you can use FFmpeg to grab all sorts of online streams, but it's not the most efficient way to go about it.
Twitch Leecher instead takes a "many hands" approach, leaving the hard reconstruction work until the last step:
Nearly all of the well known VOD downloaders execute the download process via FFMPEG's integrated download capabilities. However, this is extremely slow. The download speed rarely exceeds 1.5Mbit even if the internet connection is 100 times faster. Twitch Leecher does not use FFMPEG for download tasks at all. It downloads thousands of small video chunks in parallel while using all of the available bandwidth of your internet connection. As soon as all video chunks are downloaded, FFMPEG is only used to merge those chunks together in order to create a single video file again.
Twitch Leecher has both 32 and 64-bit installers and requires the .NET Framework 4.5 (comes with Windows 8 and 10, may need updating if you have Windows 7). If you're wondering how it all works, the source code is available on GitHub under the MIT license.