For some reason, the default branch of Garry's Mod still includes the Awesomium web renderer. This is from 2012 and is prone to multiple security exploits and is in general outdated. Awesomium also doesn't include support for modern web security standards such as TLS 1.2 and 1.3.

For this reason, we highly reccommend players opt-in to use the Chromium branch to improve their security and so that the in-game functionality works correctly.

How to Opt-In to the Chromium Branch

1. Open Steam
2. Find "Garry's Mod" in your library.
3. Right click on "Garry's Mod" and click on "Properties"
4. Go to the "Betas" tab.
5. From the dropdown on "Beta Participation" dropdown, select "x86-x64 - Chromium + 64-bit binaries"
6. Close the game properties
7. Steam will now download the x64 branch. All in-game web renderers will now use Chromium rather than Awesomium.