1. HTML reserved characters like < > and \.
2. overflowing content
3. displaying ASCII made with special encodings and characters sets, like code page 437
4. displaying nonprintable (control) characters
5. displaying colors
6. text preprocessors messing up the formatting
https://terminoid.com/discover/
i still need to add seeking and stuff, but it works. like asciinema but based on xterm.js