A practical, app-by-app rundown. Last checked May 2026 — platforms change this stuff often.
Most styles work in most places, because it's all real Unicode. The exceptions are username fields (the strictest) and a handful of apps with limited fonts that render some glyphs as boxes. When in doubt, use Bold (sans), Small Caps, or Full-width — those survive the widest range of apps.
Bio: yes — fancy text displays fine. Captions and comments: yes. Username (the @handle): the strictest field Instagram has — it rejects most combining-mark styles and some decorative ones. Story text uses Instagram's own fonts, so pasting fancy text there is hit-or-miss. If your username won't take a style, the bio almost always will.
Bio and captions: yes, including full-width / 'aesthetic' text and small caps. Username: stricter, similar to Instagram. Comments: generally fine.
The most permissive of the lot. Messages: almost everything renders, including heavy decoration — though Discord caps extreme zalgo to stop layout abuse. Nicknames and 'About Me': most styles work; the very heavy combining-mark ones can get truncated. Custom status: usually fine. Note that Discord's own **bold** and ~~strikethrough~~ markdown works in messages but not in nicknames — that's where a Unicode bold/strikethrough comes in handy.
Posts: yes, all styles. Bio: yes. Display name: mostly yes, but it can trim or reject some combining-mark styles. Handle: can't be changed to fancy characters at all — handles are restricted to plain letters, numbers and underscores.
WhatsApp: works in messages, status text and 'About' — though rendering of combining marks varies between Android and iOS. Telegram: works in messages and bio; usernames are restricted.
Highly variable, and they change their name filters often. The clean styles — Bold (sans), Full-width, Small Caps — pass most game name filters. Glitch / zalgo and stacked-mark styles usually don't. If a name bounces, drop to Bold and try again.
LinkedIn: works in posts and headlines; strips it from some profile fields. Facebook: works in posts, comments and bio. YouTube: works in comments, channel descriptions and (mostly) channel names; community posts too.
Those little rectangles mean the app's font doesn't have a glyph for that character. It's not corruption and it's not fixable from the tool side — pick a different style. The further down the 'exotic' scale a style is, the more likely you'll hit this. Bold and Small Caps almost never box out.