From what I've heard, at least some of those extensions work by faking the user agent as IE8 and will break as soon as Google discontinues support for it.

Whoa. It really is the old compose.

Does that exist for Firefox?

Wow it does exist for Firefox https://addons.mozilla.org/firefox/addon/restore-your-gmail-...

Will examine the source.

Is there something similar for Firefox?

How does this work? Why did they obfusicate their JS? Do I want to trust them?

chrome["webRequest"]["onBeforeSendHeaders"]["addListener"](function (a) { var b = a["requestHeaders"]; b[forEach](function (c, d) { if (c["name"]["toLowerCase"]() =="user-agent") { c["value"] = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)",; }; }); return { requestHeaders: _0xb56fx2 }; }, { urls: ["http://mail.google.com/*", "https://mail.google.com/*", types: ["main_frame", "sub_frame"] }, ["blocking", requestHeaders);

It actually really just swaps the user-agent for the ie8 header.

Using the Basic HTML version also helps a bit. :)

I love the Basic HTML version even though it's ugly, but I don't think it's for everyone. (Having said that, it's definitely worth giving it a try)