The default branch of Garry's Mod uses Awesomium for showing HTML or any webpage content. However, Awesomium is very outdated and doesn't support many HTML5 features.

(Warning from the Valve Developer wiki)

(Notes from the Garry's Mod wiki)

Being aware of this, I've tried my best to make BonChat accessible and look the same for both the default and x86-64 branch, but of course some stuff is just not possible to fix without switching to x86-64 which uses the more modern-friendly Chromium.

These are the known differences/bugs I'm aware of if you decide to use Awesomium with BonChat, from severe to barely a problem:

• Compared to Chromium, Awesomium is slower and laggy I've made multiple adjustments to BonChat so it's less resource intensive and more optimized, yet with enough messages, or images present in the chatbox, Awesomium will quickly come to a crawl trying to load them all. There are convars available where you can limit the amount of messages, or disable any attachment loading to avoid this (you can also disable BonChat entirely if you prefer the default chatbox).
• Loading content from websites will not work if the site is HTTPS and doesn't support TLS 1.0 (Awesomium only supports up to TLS 1.0 which is pretty bad since it's considered deprecated and a vulnerability) This will affect loading any message attachments and trying to view a webpage in the chatbox's browser panel (instead, the panel will not be used and you will just be prompted to open the page in the Steam overlay browser). I've fixed this with images by using GLua to try and do a http GET request, which doesn't have this limitation, if the content fails to load. But this will still fail in some cases such as with Discord where their Cloudflare has blocked any http requests from Garry's Mod due to api abuse. You will not be able embed content from their site (Chromium luckily supports TLS up to 1.3, and thus this isn't an issue when you try and paste a link into the chatbox, or try to click a link and open the webpage in the browser panel).
• Some modern file formats such as .webp and .webm only have partial support in Awesomium and will fail to load Note: Chromium does support most popular file formats, BUT it does not come with the codecs for many of those formats (thanks to those popularly used formats being proprietary and distributing them with GMod would lead to legal issues). But .webp and .webm are open source so they can be used, so you should be able to send and view those without any problems. If you do want to be able to use codecs such as H.264 (MP4) and AAC, you can install them yourself: GModCEFCodecFix (Of course, other people will also have to install these codecs themselves too in order to see what you send).
• Image clipboard pasting does not work I believe this is due to Awesomium not supporting the File constructor (but it still has FileReader support?)
• Font may render differently/incorrectly This differs between users, but you might be able to fix this yourself by replacing it in your system fonts (BonChat uses "Verdana" same as the default chatbox. From my testing I actually like Awesomium's sharp font over Chromium's aliased font, so this bug is really a preference thing).
• Some small quirks with the chatbox that are slightly different across branches These are mostly visual differences and don't affect the performance of the addon.

Hopefully this convinces you to NOT use Awesomium because it is garbage compared to Chromium. Please use the x86-64 branch.

(If you do manage to find a real fix for any of these and are able to provide instructions or code, I'd appreciate if you contact me so I can try and fix it)