★ Dev formats · regex

Regex for UUID

Matches hyphenated UUIDs of versions 1 to 8 (including v4 random and v7 time-ordered) with the RFC variant. The nil and max UUIDs (all zeros or all f's) are special values and don't pass.

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Try the uuid pattern

Read it in plain English (best-effort)

^start of a line
[0-9a-fA-F]one character from: 0–9, a–f, A–F
{8}exactly 8 of the previous
-the character '-'
[0-9a-fA-F]one character from: 0–9, a–f, A–F
{4}exactly 4 of the previous
-the character '-'
[1-8]one character from: 1–8
[0-9a-fA-F]one character from: 0–9, a–f, A–F
{3}exactly 3 of the previous
-the character '-'
[89abAB]one character from: '8', '9', 'a', 'b', 'A', 'B'
[0-9a-fA-F]one character from: 0–9, a–f, A–F
{3}exactly 3 of the previous
-the character '-'
[0-9a-fA-F]one character from: 0–9, a–f, A–F
{12}exactly 12 of the previous
$end of a line

Test text

One sample per line works well with the m flag on anchored patterns.

Waiting for a pattern

The pattern, piece by piece

/^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/

Pattern explanation
Part	What it does
`[0-9a-fA-F]{8}`	8 hex digits
`-[0-9a-fA-F]{4}`	4 hex digits
`-[1-8][0-9a-fA-F]{3}`	the version digit (1–8) then 3 hex digits
`-[89abAB][0-9a-fA-F]{3}`	the variant: first digit 8, 9, a or b
`-[0-9a-fA-F]{12}`	12 hex digits

What it accepts and rejects

Every sample below is checked automatically in JavaScript and Python. The tester above is preloaded with all of them, one per line.

Should match
Should match
`123e4567-e89b-12d3-a456-426614174000`	✓
`550e8400-e29b-41d4-a716-446655440000`	✓
`f47ac10b-58cc-4372-a567-0e02b2c3d479`	✓
`018f3b1e-7c3a-7d4e-9f00-1a2b3c4d5e6f`	✓
`6BA7B810-9DAD-11D1-80B4-00C04FD430C8`	✓
`a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11`	✓

Should not match
Should not match
`123e4567e89b12d3a456426614174000`	✗
`123e4567-e89b-02d3-a456-426614174000`	✗
`123e4567-e89b-12d3-c456-426614174000`	✗
`00000000-0000-0000-0000-000000000000`	✗
`g23e4567-e89b-12d3-a456-426614174000`	✗
`{123e4567-e89b-12d3-a456-426614174000}`	✗

Copy it into your code

RE2-safeNo lookarounds or backreferences, so the same pattern works in Go's RE2 engine and in Rust's regex crate.

Language

const uuidRe = /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/;

export function isValidUuid(value) {
  return uuidRe.test(value.trim());
}

When not to use regex for this

If you only need 'is this a UUID my code can parse', use your UUID library's parser. In Postgres, a uuid column rejects bad values for free.

Questions engineers actually ask

Does it match UUID v7?

Yes. Version digits 1 through 8 are accepted, which covers v7's time-ordered IDs.

Why doesn't the nil UUID match?

00000000-0000-0000-0000-000000000000 has version 0, a special value rather than a generated ID. Add it explicitly if your system uses it.

What is catastrophic backtracking?

Some patterns, usually nested quantifiers like (a+)+, make a backtracking engine try an exponential number of paths on input that almost matches. The tester stops any run after 300ms, so a bad pattern can't freeze your tab. In production, that same pattern can take down a server (a ReDoS attack).