Tells you whether your chosen handle is even allowed on each platform — before you go check availability.
No need to add @ — just the handle text.
Common gotchas
Leading numbers — banned on Twitter, GitHub, LinkedIn. Allowed on Instagram (mostly) and TikTok.
Periods (.) — only Instagram + TikTok allow them. Useful for first.last style
Hyphens (-) — only GitHub and Bluesky (in domains). Banned elsewhere
Length — Twitter is the strictest (15 chars max). LinkedIn allows the longest custom URLs (100 chars)
Case — handles are technically case-insensitive everywhere, but display preserves the case you registered
Choosing a cross-platform handle
If you want the same handle on every platform, optimize for the strictest rules — that's Twitter / X. Stick to letters, digits and underscores, no leading number, 4-15 characters and you're safe everywhere.
Privacy
Validation happens in your browser via regex. Nothing is uploaded.