For mobile users specifically on Opera Mini, the process differs slightly from the desktop's sidebar approach:
Within
When a user navigated to Facebook Chat via Opera Mini, the request was sent to Opera’s servers. These servers retrieved the full Facebook page, executed the JavaScript, and rendered the page. The server then compressed the page into a proprietary binary format (OBML - Opera Binary Markup Language) and sent it to the user's device. This process stripped heavy elements and resized images, drastically reducing data consumption. facebook chat with opera mini verified