I'm just wondering cause one of it is mb and one is kb

The first two links will serve you the small online stub installer for Windows while the last one will serve you the full offline installer you choose for 64-bit or 32-bit (for Windows).

What is a stub installer?

https://firefox-source-docs.mozilla.org/browser/installer/windows/installer/index.html https://firefox-source-docs.mozilla.org/browser/installer/windows/installer/StubConfig.html

The full setup allows you do things like custom install location.

It is only for Windows as there are no installers for macOS and Linux.

So stub installer and installer both install firefox?

The stub installer just is a small compacted version?

And like this: https://youtu.be/UWAVTpJUmrw?si=jxaNlxz4m0y4_mN1 is an online stub download?

The stub installer needs an internet connection as it does not contain the application but rather downloads and installs it.

Ah so it installs it over the internet but it's still firefox right? after it downloads?