Automatically set Youtube video resolution to a low definition. This is a fork of Auto HD for YouTube, keeping only low definition options and defaulting to medium (360p), so that people wanting to reduce their environmental footprint can just install it and forget about it.
As I couldn't find the original repository, this fork was done from the .xpi provided at [https://addons.mozilla.org/firefox/downloads/file/1702548/auto_hd4k8k_for_youtubetm-1.0.4-fx.xpi], but that archive doesn't include a license, so re-licensing here would be weird.