Master Regular Expressions in Real-Time
Write, test, and visualize regex patterns instantly — no setup, no boilerplate, just pure pattern-matching clarity. Trusted by 48,000+ developers worldwide.
See Your Regex Come Alive
Type a pattern, paste your text, and watch every match, capture group, and zero-width assertion render in real time. The editor updates on every keystroke — no "run" button required.
![RegExLab editor interface with a dark-themed code panel on the left showing the pattern (\\b[A-Z][a-z]+\\b) and a results panel on the right highlighting matched words in green with numbered capture groups](assets/02-editor-ui.jpg)
The live preview engine supports all major regex flavors: PCRE (PHP 8.3+), ECMAScript (ES2024), Python (re & regex modules), Java (java.util.regex), and Go (RE2). Switch flavors with one click and instantly see compatibility differences — including which features like lookbehind or possessive quantifiers are supported in each engine.
Everything You Need to Tame Regex
RegExLab packs professional-grade tools into a distraction-free browser experience. Here's what makes it the go-to playground for regex work.
Syntax Highlighting & Token Parsing
Every token in your pattern — quantifiers, anchors, character classes, groups — is color-coded and labeled on hover. Spot typos like misplaced backslashes or unescaped brackets before they ship to production.
Step-by-Step Execution Visualization
Watch your regex engine walk through the input string character by character. See backtracking steps, failed branches, and successful matches with a timeline you can scrub forward and backward.
5 Regex Flavors, One Interface
Test against PCRE, ECMAScript, Python re, Java, and Go RE2 simultaneously. A compatibility matrix flags unsupported features per flavor so you never deploy a pattern that silently fails on your target runtime.
Capture Group Inspector
Named and numbered groups are extracted into a clean table with their values, start/end offsets, and overlap relationships. Export group data as JSON or CSV for use in your pipeline.
Regex Library & Snippets
Browse 340+ community-curated patterns — email validation, URL parsing, IPv6 extraction, log-line dissecting — and fork them directly into your workspace. Each snippet includes explanation and test cases.
Share & Embed
Generate a permanent URL for any pattern + test text combo. Embed a live mini-editor in your docs, README, or team wiki with a single iframe tag. Perfect for onboarding and code reviews.
Trusted by Developers Who Ship Regex Daily
RegExLab is open-source under the MIT license and backed by a community that values clarity over cleverness.
12,400+ GitHub Stars
The most-starred regex tool on GitHub, upvoted by engineers at companies like Stripe, Datadog, and GitLab.
48,000 Active Monthly Users
From solo hackers to enterprise teams, developers across 90+ countries use RegExLab to validate patterns before deployment.
99.97% Uptime (2024)
Hosted on a globally distributed edge network with automatic failover. Your patterns are always one click away.
What Developers Are Saying
"Saved me 3 hours on a log-parsing regex"
The step-by-step visualization showed exactly where my lookbehind assertion was failing. I fixed the pattern in under two minutes and shared the result with my team via the embed link. — Priya Menon, Senior SRE at PagerDuty
"The only regex tool I bookmarked"
I've tried Regex101, regexr, and at least a dozen others. RegExLab's multi-flavor support and capture group inspector are unmatched. It's now the first tab I open when writing any regex-heavy code. — Marcus Chen, Backend Engineer at Shopify
"Perfect for teaching regex to juniors"
The token highlighting and execution timeline make abstract concepts like backtracking and zero-width assertions tangible. My team's code review comments about regex bugs dropped by 60% after we adopted RegExLab. — Aisha Okafor, Engineering Manager at Figma
Common Questions
Is RegExLab free to use?
Yes. RegExLab is completely free and open-source under the MIT license. There are no paywalls, no feature gates, and no account required. You can also self-host it from the public GitHub repository.
Does it work offline?
The core editor and regex engine run entirely in your browser via WebAssembly. You can use RegExLab without an internet connection — only the snippet library and share-link generation require connectivity.
Which regex flavors are supported?
RegExLab supports PCRE (PHP 8.3+), ECMAScript (ES2024), Python (re and regex modules), Java (java.util.regex, Java 21), and Go (RE2). Each flavor has its own compatibility matrix so you can see exactly which features are available.
Can I use RegExLab patterns in production code?
Absolutely. RegExLab is a testing and visualization tool — the patterns you write are standard regex syntax. Copy them directly into your codebase. The flavor selector ensures what you test is what you deploy.
Stop Guessing. Start Matching.
Join 48,000 developers who write cleaner, faster, and more reliable regular expressions with RegExLab. No signup, no download — just open the editor and start typing.