Fix Media: x86-64 / GModCEFCodecFix Guide (FAQ)

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What is the x86-64 beta?

The x86-64 beta is a beta for Garry's Mod that enhances it with 64-bit builds, larger memory limits, a newer version of LuaJIT, and most importantly replaces Awesomium with gmod-html and Chromium Embedded Framework.

What are Awesomium / gmod-html / Chromium Embedded Framework?

Chromium Embedded Framework, aka CEF, is an embeddable and open-source version of Google Chrome that can be used in games and other applications.

It's basically GMod's built-in web browser. It's what allows gamemodes/addons like YukiTheater, Cinema, and Media Player to work.

gmod-html is the "glue" that connects GMod to CEF in the x86-64 beta.

Awesomium is a very old version of CEF that was never updated beyond Chrome 18 (circa 2012).

It can't connect to or interact with most websites now, but is still included on the main (non-beta) version of GMod.

What is GModCEFCodecFix?

GModCEFCodecFix is a tool that patches Garry's Mod, fixing many common issues playing videos/audio with CEF.

Using our custom fork of gmod-html, it:

Is GModCEFCodecFix open source? Can I support the project somehow?

Yes it is! The GitHub repo can be found here:

You can also find the GitHub repo for our fork of gmod-html, here:

💖 If you'd like to support the project, consider throwing a few dollars our way! You can also help us by contributing code directly with Pull Requests.

I have no in-game menu after a GMod update / GMod suddenly stopped working even though I've applied the fix

Updates to Garry's Mod tend to wipe out our patches. You will need to go to Steam > Garry's Mod > Properties > Installed Files and click Verify integrity of game files.

Once Steam is done updating/verifying GMod, run GModCEFCodecFix again to reapply the patches.

I'm still getting a "Does Not Match" error even after verifying game integrity

It's likely a recent GMod update made our patches incompatible with it, so we'll have to regenerate/update them.

This automatically happens every 6-7 hours, but we can sometimes trigger it sooner.

Contact Us if you run into this error and don't want to wait for the automatic regeneration!

I have no main menu on Linux even after applying the fix

CEF isn't being initialized. This usually means the game doesn't have access to unprivileged user_namespaces.

There are two common causes for this:

I'm getting "Error: Could not detect GMod EXE Launch Options!" on Linux

There's a bug with Steam where GMod's Proton state in Steam doesn't match the actual state.

Toggle Proton with Steam > Garry's Mod > Properties > Compatibility > Force the use of a specific Steam Play compatibility tool, then try again.

I have no main menu or the game isn't opening on macOS even after applying the fix

First, go to Steam > Garry's Mod > Properties > General > Launch Options and make sure the following is NOT present:


If it is, remove it and try again. If it isn't, try again anyway. GMod tends to crash the first time right after applying the patches on macOS.

If it's still crashing, go to Steam > Garry's Mod > Properties > General > Launch Options and add this to temporarily disable your addons:

-noaddons -noworkshop

There's a known issue with GMod on macOS where some addons will cause the game to crash on startup.

If it works with addons disabled, try removing them until you've found the one that's causing you to crash.

If it still crashing with the addon-disabling launch options, Contact Us, providing the following information:

Please keep in mind that support for GMod on macOS is unfortunately not very reliable.

I want to completely uninstall GModCEFCodecFix. How do I do that?

  1. Go to Steam > Garry's Mod > Properties > Installed Files and click Verify integrity of game files. This will remove the changes made to the game files.
  2. Delete the GModCEFCodecFix executable you downloaded.
  3. Remove the temporary files directory. On each operating system, it can be found at:
    • Windows: %LOCALAPPDATA%\Temp\GModCEFCodecFix
    • macOS: /Library/Caches/GModCEFCodecFix
    • Linux / ChromeOS: $XDG_CACHE_HOME/GModCEFCodecFix

For most users, just following Step 1 will achieve the desired effect. The other steps just delete any remnants of the tool from your storage.