★ Dev formats · regex

Regex for Semantic Version

The regex published by semver.org for SemVer 2.0.0. It captures major, minor, patch, pre-release and build metadata, and rejects leading zeros in numeric parts.

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Try the semantic version pattern

Read it in plain English (best-effort)

^start of a line
(start capture group 1
0the character '0'
|or
[1-9]one character from: 1–9
\da digit (0–9)
*zero or more of the previous
)end of group
.the character '.'
(start capture group 2
0the character '0'
|or
[1-9]one character from: 1–9
\da digit (0–9)
*zero or more of the previous
)end of group
.the character '.'
(start capture group 3
0the character '0'
|or
[1-9]one character from: 1–9
\da digit (0–9)
*zero or more of the previous
)end of group
(?:start a group (not captured)
-the character '-'
(start capture group 4
(?:start a group (not captured)
0the character '0'
|or
[1-9]one character from: 1–9
\da digit (0–9)
*zero or more of the previous
|or
\da digit (0–9)
*zero or more of the previous
[a-zA-Z-]one character from: a–z, A–Z, '-'
[0-9a-zA-Z-]one character from: 0–9, a–z, A–Z, '-'
*zero or more of the previous
)end of group
(?:start a group (not captured)
.the character '.'
(?:start a group (not captured)
0the character '0'
|or
[1-9]one character from: 1–9
\da digit (0–9)
*zero or more of the previous
|or
\da digit (0–9)
*zero or more of the previous
[a-zA-Z-]one character from: a–z, A–Z, '-'
[0-9a-zA-Z-]one character from: 0–9, a–z, A–Z, '-'
*zero or more of the previous
)end of group
)end of group
*zero or more of the previous
)end of group
)end of group
?the previous is optional
+15 more

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|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$/

Pattern explanation
Part	What it does
`(0\|[1-9]\d*)`	groups 1–3: major, minor, patch, with no leading zeros
`(?:-(…))?`	group 4: optional pre-release like alpha.1
`(?:\+(…))?`	group 5: optional build metadata like +exp.sha.5114f85

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
`1.0.0`	✓
`0.1.0`	✓
`2.10.3`	✓
`1.0.0-alpha`	✓
`1.0.0-alpha.1`	✓
`1.0.0+20130313144700`	✓
`1.0.0-beta+exp.sha.5114f85`	✓

Should not match
Should not match
`1`	✗
`1.0`	✗
`01.0.0`	✗
`1.0.0-`	✗
`1.0.0-01`	✗
`v1.0.0`	✗
`1.0.0+`	✗

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 semverRe = /^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$/;

export function isValidSemver(value) {
  return semverRe.test(value.trim());
}

When not to use regex for this

To compare or sort versions, use a semver library (semver on npm, golang.org/x/mod/semver). Precedence rules for pre-releases are subtle.

Questions engineers actually ask

Why doesn't v1.0.0 match?

The 'v' prefix is a tag convention, not part of SemVer. Strip it before validating.

Is 1.0.0-01 valid?

No. Numeric pre-release identifiers can't have leading zeros under SemVer 2.0.0.

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).