Write a pattern and test string — matches highlight as you type. Inspect capture groups, switch to replace or split, and read a plain-English breakdown of every token. Nothing leaves your browser.
The link will also carry your {{text.length}}-character test string — anyone with the link can read it.
Save example strings the pattern should — or should not — match, so a later edit can't silently break them.
| # | Match | Line / Range | Groups |
|---|---|---|---|
| {{i+1}} | {{m.text===''? '∅ (empty)' : m.text}} | {{m.lineLabel}}[{{m.start}}–{{m.end}}] | — ${{gi+1}} {{g===undefined?'(none)':g}} {{n.k}} {{n.v===undefined?'(none)':n.v}} |
{{ workerReplaced }}| Index | Chunk | Length |
|---|---|---|
| [{{ i }}] | {{ p === '' ? '∅ (empty string)' : p }} | {{ p.length }} char{{ p.length === 1 ? '' : 's' }} |
{{r[0]}}{{r[1]}}Uses your browser's native RegExp engine, so matches, replace and split behave exactly like they would in JavaScript — the explainer just walks the pattern token by token and describes each one in plain English. Matching, replace and split run in a background Web Worker with a time limit, so a runaway pattern (catastrophic backtracking) can't freeze the page.
Test cases save example strings the pattern should or shouldn't match — including expected capture groups for positive cases — and stay saved in this browser so a later edit can't silently break them. Saved patterns work the same way for the pattern itself. Both are stored only in this browser's local storage, never uploaded.
Share builds a link with just the pattern and flags by default. Including the test string is a separate, explicit checkbox with a preview of what that adds — it's off by default since pasted test text can contain data you didn't mean to put in a URL.
Everything runs locally as you type. Your pattern and test string are never sent anywhere on their own — only if you build a share link yourself and send it, and then only with the test string if you explicitly opted that in.
