A free regex visualizer and online regex tester for JavaScript regular expressions: live match highlighting, capture groups, token explanations, replace preview, unit tests, and shareable links — in your browser, with no signup.
Uses your browser's JavaScript RegExp flavor — not PCRE, .NET, or Python re. For HTML editing use HTML Viewer Pro; for email HTML use Email Viewer.
Enter a pattern, inspect matches, then replace or share.
Paste a pattern between the slashes, add test text, and toggle flags (g i m s u y).
Step through hits, read token notes, and check numbered or named capture groups with color cues.
Preview substitutions, run unit cases, compare patterns in Diff, or copy a share link from the URL hash.
Debug patterns, validate fields, and learn as you type.
See exactly what matched and which groups are empty. Token notes explain classes, quantifiers, groups, and anchors.
Confirm emails, dates, or URLs before shipping code. Prototype $1 / named backreferences safely.
Patterns and sample text stay in your browser for core testing. See the Privacy Policy.
Live highlighting, Prev/Next stepping, plain-English summary, group inspector, Diff mode, unit tests, history, favorites, and code export. Students learn with live feedback; developers debug validation rules and scrapers; educators demo greedy matches without an IDE — same free tool for everyone, with no account wall.
Prefer a walkthrough? Open the RegEx Visualizer guide or browse the Regex visualizer blog. Related apps live on the Tools Viewer homepage.
A regex visualizer shows how a regular expression matches text — highlighting hits, listing capture groups, and explaining tokens — so you can debug patterns without guessing. ToolsViewer’s RegEx Visualizer combines a live tester with an explainer in one browser workspace.
Yes. ToolsViewer’s RegEx Visualizer & Explainer is free with no signup. Pattern testing, explanations, unit cases, replace preview, and share links all run in your browser.
It uses the JavaScript RegExp engine in your browser (ECMAScript). Flags g, i, m, s, u, and y are supported where the browser allows them. It is not a PCRE, .NET, or Python re emulator.
No. Patterns, test strings, and replacements stay on your device for core testing unless you copy, export, or share a URL hash yourself.
Yes. Each match lists numbered and named capture groups with color cues so you can verify what each group captured, including empty groups.
Yes. The explainer breaks the pattern into tokens — literals, character classes, quantifiers, groups, anchors, and more — with plain-language notes as you edit.
Yes. Enter a replacement string (including $1 / $<name> style backreferences) and preview the result live next to your matches before you copy it into code.
Yes. Use Share link to copy a URL that restores your pattern, flags, and test string from the hash — nothing is stored on our servers for that handoff.
Yes. Use the RegEx Visualizer blog cheat sheet for character classes, anchors, quantifiers, and groups, then practice the same patterns in this tool or follow the full screenshot guide.
No. Open RegEx Visualizer in your browser, paste a pattern and sample text, and follow along. Optional preferences stay in local storage on your device when available.