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Regex Backreference & Named Group Visualizer

Regex

Parse a regex pattern and list every capture group (numbered and named) and every backreference, flagging a backreference that points at a group that doesn't exist or hasn't finished being defined yet at that point in the pattern

Paste a regex pattern and this parses out every capture group, numbered and named, alongside every backreference, then checks each backreference against the groups it could plausibly resolve to. A backreference that points at a group index or name with no matching group, or at a group whose closing parenthesis hasn't been reached yet at that point in the pattern, is flagged since it either always matches empty or throws depending on the engine. This is a structural, non-AI check, distinct from the Regex Explainer (AI), which gives a general prose breakdown, and the ReDoS Detector, which checks catastrophic backtracking risk instead of group correctness. It doesn't run the pattern against real input, so it can't tell you whether the groups themselves are well-formed for your matching intent, only whether the backreferences wired between them are structurally sound.

regexgroupsbackreferencecapture-groupnamed-grouplint

How to use Regex Backreference & Named Group Visualizer

  • 1.Paste a regex pattern's body only, without delimiters or flags, into the input box.
  • 2.Review the capture groups list to confirm numbering matches what you expect, especially once named groups are mixed in with plain numbered ones.
  • 3.Check the backreferences list and any flagged issues for a reference to a group that doesn't exist yet or was never defined, a common source of subtle regex bugs.

Frequently asked questions

Does this validate the regex will compile?
It also tries to compile the pattern with the browser's native RegExp engine and reports whether it's valid, but group and backreference analysis proceeds structurally either way, since a syntax error elsewhere in the pattern doesn't necessarily mean the group structure can't still be parsed.
What counts as a backreference that 'hasn't been defined yet'?
A backreference whose position in the pattern comes before the closing parenthesis of the group it targets, which includes both a forward reference to a later group and a group referencing itself from inside its own body, like (\1).
Does it support named groups and \k<name> backreferences?
Yes, (?<name>...) capture groups and \k<name> backreferences are parsed the same way as numbered groups and \1-style backreferences, and named groups still consume a numbered slot the way JavaScript regex actually numbers them.
Is my pattern sent to a server?
No, the browser tool runs entirely client-side. The REST API and SDKs run the same structural analysis locally with no external calls.

Use via API, SDK, or MCP

cURL# Free: 1,000 req/day · Pro: 10,000 req/day
curl -X POST https://api.utilix.tech/v1/tools/regex-groups \
  -H "Authorization: Bearer utx_live_..." \
  -H "Content-Type: application/json" \
  -d '{"pattern":"(?<year>\\d{4})-(?<month>\\d{2})\\k<year>"}'

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