Test JavaScript regular expressions with live match highlighting.
| # | Match | Index | Groups |
|---|---|---|---|
| 1 | hello@toolzer.net | 14 | — |
| 2 | support@example.com | 35 | — |
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Regular expressions are powerful but easy to get wrong. This tester evaluates any JavaScript regex against your input as you type, highlights every match, lists capture groups, and reports common errors in plain language. Use it to validate form inputs, to extract data from log lines, to build search-and-replace rules — and to learn regex without a stack of documentation.
Type or paste the target you want to inspect into the input field at the top of the page.
Click the check button — the tool queries live data sources and returns results in seconds.
Review each finding: status, score, and the reason behind every warning are listed line by line.
Follow the linked remediation guides to fix issues, or copy the report to share with your team.
When something in your stack misbehaves, half the battle is figuring out whether the problem is you, the network, or the other side. Regex Tester gives you a fast, opinionated readout so you can rule things in and out in seconds. Because the check runs on live infrastructure and reports raw results — not marketing-safe summaries — you can trust what you see and act on it. Toolzer's design philosophy is simple: privacy-first (no tracking, no accounts), performance-first (the page is interactive in under a second on a 3G connection), and honesty-first (no fake ratings, no dark patterns, no upsells). Regex Tester follows the same rules as every other utility on the site. You can bookmark this page, share the URL with a colleague, or pin it to your browser's toolbar — the experience will be identical every visit, and it will keep working even if you're on airplane Wi-Fi. Real people use this tool for real work — freelancers cleaning up client deliverables, sysadmins triaging tickets, students finishing assignments — and it is tuned for those workflows, not for demo videos.
How Toolzer compares to typical online alternatives.
| Feature | Toolzer | Typical competitors |
|---|---|---|
| Price | 100% free | Free with limits or paid |
| Signup required | No | Usually yes |
| Data privacy | Processed in your browser | Uploaded to their server |
| Watermark | Never | Often on free tier |
| File size limit | Generous / none | Usually 5–10 MB |
| Ads | Minimal | Heavy, intrusive |
| Mobile friendly | Yes | Often not |
JavaScript (ECMAScript) regex. Most modern languages share the same core, but PCRE adds extras like recursive patterns.
Greedy quantifiers match as much as possible. Lazy quantifiers (e.g. *?) match as little as possible — useful for tags and quoted strings.
Common culprits: forgetting to escape ., $ or /, leaving the g flag off when iterating, or anchoring with ^ inside a multi-line string without the m flag.
Yes, in all modern browsers. Variable-length lookbehinds work in V8, Firefox and Safari 16.4+.
No. Every utility on Toolzer is free, anonymous, and works in any modern browser without registration.
Yes. Whenever the tool can produce an answer entirely in the browser, the data never leaves your device.
Yes. The interface is fully responsive and works on iOS Safari, Android Chrome, and every modern mobile browser.
Yes. Every Toolzer page has a clean permanent URL you can bookmark or share.
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