Pattern

Regex for UUID v4 specifically

Random-generated UUID version 4.

The UUID v4 specifically regex is ^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$ — copy it below, or open it in the explainer for a token-by-token breakdown.

The pattern

^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$

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What it matches

550e8400-e29b-41d4-a716-446655440000
f47ac10b-58cc-4372-a567-0e02b2c3d479

What it doesn't match

123e4567-e89b-12d3-a456-426614174000

Notes & gotchas

Third group starts with 4 (version), fourth group starts with 8/9/a/b (variant). Most modern IDs are v4.

Code in your language

Use the explainer's Code tab to generate ready-to-paste snippets in JavaScript, Python, Java, .NET, Go, Ruby, and PHP for this pattern.

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Token-by-token breakdown

Every part of the pattern, left to right:

Token	Meaning
`^`	start of string (or line in multiline mode)
`[0-9a-fA-F]{8}`	exactly 8 times: any of: digits, a–f, A–F
`-`	literal text “-”
`[0-9a-fA-F]{4}`	exactly 4 times: any of: digits, a–f, A–F
`-4`	literal text “-4”
`[0-9a-fA-F]{3}`	exactly 3 times: any of: digits, a–f, A–F
`-`	literal text “-”
`[89abAB]`	any of: “8”, “9”, “a”, “b”, “A”, “B”
`[0-9a-fA-F]{3}`	exactly 3 times: any of: digits, a–f, A–F
`-`	literal text “-”
`[0-9a-fA-F]{12}`	exactly 12 times: any of: digits, a–f, A–F
`$`	end of string (or line in multiline mode)

About this pattern

Identifier formats like UUIDs, hashes, and version strings have well-defined structures that regex captures cleanly. The pattern verifies format; checksums and validity against a registry need additional checks.

Quick usage in different languages

This exact pattern — with the correct escaping and idioms for each language:

JavaScript: /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/.test(value)
Python: re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value)
Java: Pattern.compile("^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$").matcher(value).matches()
C# / .NET: Regex.IsMatch(value, @"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$")
Go: regexp.MustCompile(`^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$`).MatchString(value)
Ruby: /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/.match?(value)
PHP: preg_match('~^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$~', $value)

The explainer’s Code tab regenerates these for any pattern you paste, and the downloadable cheat sheet bundles the breakdown, all seven snippets, and the pitfalls below onto one printable page.

Common pitfalls

Anchored to the whole string. This pattern uses ^ and $, so it requires the entire input to match. To find it inside a longer text, drop the anchors and use the global (g) flag.
Case sensitivity. Letter ranges are case-sensitive — use the i flag if the input case can vary.
Validate beyond format. Matching the format doesn't guarantee the value is real. Confirm the uuid v4 specifically against a source of truth (database, API, or checksum) where it matters.

Standards & sources

This pattern is based on the following authoritative specification(s) and issuing authorities. Formats can change — always confirm against the primary source.

RFC 9562 — Universally Unique IDentifiers (UUIDs)

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