Username Format Validator

Instantly see which platforms accept your handle and which reject it - with a clear reason for every failure.

Researched by NameSniper ResearchVerified October 2026We verify platform rules against official sources and re-check regularly.

Why format rules vary

Every platform has its own rules for what characters are allowed, where dots can appear, whether consecutive underscores are permitted, and how capitalization is treated. A handle with a period can pass on Threads and fail on Twitch; one with a hyphen can pass on GitHub and fail on Instagram.

The safest cross-platform pattern

If you want one handle that passes the format rules on every platform we check:

  • 5-15 characters. Snapchat and X (Twitter) set the 15-character ceiling; Telegram and X (Twitter) need at least 5.
  • Lowercase letters and numbers. Capital letters are rejected by npm.
  • Start with a letter. A leading digit is rejected by Snapchat and Telegram.
  • Skip separators if you can. The underscore is rejected by Bluesky and GitHub. The period is rejected by GitHub, Kick, Pinterest, Roblox, Telegram, Twitch, and X (Twitter). The hyphen is rejected by Instagram, Kick, Pinterest, Roblox, Telegram, Threads, TikTok, Twitch, and X (Twitter). If you need one, the underscore is rejected by the fewest.

A plain lowercase handle of letters and numbers in that length range passes format validation on every platform we check. Type it into the validator above to confirm.

Username rules by platform

Every platform in the validator, with its sign-up length and allowed characters. Each rule links the official page it comes from; where a platform doesn’t publish a rule, the note says what we use instead.

  • Bluesky: 3-253 characters; letters, numbers, hyphens (-) - case-insensitive (stored lowercase). Short form like "alice" (auto-appends .bsky.social) or full DNS like "alice.bsky.social". The protocol allows 253 characters, but Bluesky's help center caps custom-domain handles at 30. Rule source
  • GitHub: 1-39 characters; letters, numbers, hyphens (-) - no leading, trailing, or consecutive hyphens. Rule source
  • Instagram: 1-30 characters; letters, numbers, periods (.), underscores (_) - no consecutive periods, cannot start or end with a period. Instagram's help center doesn't publish these rules; they are what Instagram's own sign-up form enforces (checked October 2026). Rule source
  • Kick: 4-25 characters; letters, numbers, and underscores (_). Kick publishes only the 25-character maximum. Its sign-up form confirmed the character set and maximum in October 2026; the 4-character minimum was observed there in August 2026. Rule source
  • LinkedInRules only, not checked: 3-100 characters; letters, numbers, hyphens (-). Rule source
  • Linktree: 1-50 characters; letters, numbers, periods (.), underscores (_), hyphens (-). Linktree doesn't publish exact length or character limits. Rule source
  • npm: 1-214 characters; lowercase letters, numbers and hyphens (-). npm's docs only mention lowercase letters, hyphens and numbers; its own validator also accepts periods, underscores and ! ~ * ( ). Rule source
  • Pinterest: 3-30 characters; letters, numbers, underscores (_) - must include at least one letter. Rule source
  • RedditChecking paused: 3-20 characters; letters, numbers, underscores (_), hyphens (-). Reddit Help does not state the length or character limits. Rule source
  • Roblox: 3-20 characters; letters, numbers, at most one underscore (_) - not as the first or last character. Rule source
  • Snapchat: 3-15 characters; letters, numbers and one hyphen (-), underscore (_) or period (.) - must start with a letter and end with a letter or digit. Rule source
  • SubstackChecking paused: 4-32 characters; letters and numbers only. Rule source
  • Telegram: 5-32 characters; letters, numbers, underscores (_) - must start with a letter, no consecutive or trailing underscores. Telegram publishes 5-32 characters, a-z, 0-9 and underscores; the start, end and double-underscore rules are not published. Rule source
  • Threads: 1-30 characters; letters, numbers, periods (.), underscores (_) - no consecutive periods, cannot start or end with a period. Threads doesn't publish its username rules; profiles created with Instagram follow Instagram's. Rule source
  • TikTok: 2-24 characters; letters, numbers, underscores (_) and periods (.) - cannot end with a period. Rule source
  • Twitch: 4-25 characters; letters, numbers, underscores (_). Twitch does not publish which characters a username may start with. Rule source
  • X (Twitter): 5-15 characters; letters, numbers, and underscores (_) only. Rule source
  • YouTube: 3-30 characters; letters and numbers in any of YouTube's 75 supported languages, underscores (_), hyphens (-), periods (.), middle dot (·) - cannot start or end with a separator. Rule source

Labelled rows are reference only: we don't check LinkedIn availability at all, and checks on Reddit and Substack are paused, so their rules are here for reference.

Building a validator of your own? A machine-readable version of these rules - length limits, regex patterns, and platform quirks - is published as a free dataset at github.com/NameSniperPro/username-rules (CC BY 4.0).

Frequently Asked Questions

Can I use dots in an Instagram username?

Yes. Instagram accepts periods, but not at the start or end of a username and never two in a row. Underscores are more forgiving: a leading or trailing underscore, or two in a row, is accepted. Instagram's help center doesn't publish these rules; they are what its own sign-up form enforces.

Can I use special characters on TikTok?

Only underscores and periods. TikTok usernames are 2-24 characters of letters, numbers, underscores and periods, and the only placement rule TikTok publishes is that a username can't end with a period. Hyphens, spaces and other symbols are rejected.

Does this check username availability?

No. This tool only tests format validity (characters, length, platform rules). To check if a username is actually available on each platform, use the full NameSniper checker.

Can I use emoji in usernames?

No. None of the platforms in the validator accepts emoji in a username. Display names and bios are where emoji go - see the Social Media Character Limits tool for those limits.

Why does Bluesky accept my handle without a domain?

Bluesky uses DNS-style handles that look like alice.bsky.social. When you type just the short part (like alice), Bluesky appends .bsky.social during sign-up. The validator accepts both forms.

Can I use capital letters in usernames?

Where platforms say so, usernames are case-insensitive: YouTube, Bluesky and Telegram state it outright, so BrandName and brandname are the same handle. npm is the exception: it rejects capital letters instead of treating them as lowercase. Lowercase everywhere is the safe choice.

Which platforms allow hyphens in usernames?

Among the platforms we check, hyphens are accepted by Bluesky, GitHub, Linktree, npm, Snapchat, and YouTube and rejected by Instagram, Kick, Pinterest, Roblox, Telegram, Threads, TikTok, Twitch, and X (Twitter). None of them explains why. If you need a word break, the underscore is rejected by the fewest platforms we check.

Can I use international or non-Latin characters?

YouTube is the exception among the platforms we check: handles can use letters from many languages, with different length limits for some scripts. Platforms that publish a character set otherwise limit usernames to Latin letters, numbers and a few separators, so for one identity everywhere, stick to lowercase a-z and 0-9.

Does this check reserved words or trademarks?

No - the validator checks length and characters only. Some platforms also block certain words: X won't let a username contain "Admin" or its own brand name, and LinkedIn profile URLs can't contain "linkedin". For trademark conflicts, Day Pass, Pro, and Business include on-demand USPTO trademark screening.

Check All Platforms at Once

Don't check one platform at a time. NameSniper checks domains and social handles in a single search, with optional USPTO trademark screening.

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