Regex Tester & Debugger
Private by design — runs entirely in your browser
Test regular expressions against sample text in your browser. Toova shows live match highlights, capture group results, replacement output, and explains common errors — all without uploading your regex or your test input.
Live matches and capture groups
Type or paste a regex and a sample, and Toova highlights every match in the text as you type. Hover over a match to see the captured groups, both numbered and named. The match index is shown next to each occurrence, which helps when debugging a regex that catches too much or too little. Toggle flags (global, case-insensitive, multiline, sticky, unicode) and the highlights update instantly.
Replace mode
Switch to replace mode and supply a replacement string. The output panel shows the transformed text in real time. Capture groups are available as $1, $2, named groups as ${name}. This is the right tool for prototyping search-and-replace operations before running them across a codebase or a database column — see the result first, then apply it where it counts.
Browser-only, no upload
Every regex evaluation runs in your browser. The pattern and the test text never leave the page. That matters when you are debugging a regex on production log lines, customer messages, or anything sensitive. The page works offline after first load and the Network tab will stay empty while you test.
Frequently Asked Questions
- Which regex flavor does this support?
- JavaScript's regex engine, which is also what Node.js uses. That covers most modern web stacks. Lookbehind, named groups, and Unicode property escapes are all supported.
- What do the flags mean?
- g matches all occurrences (not just the first). i is case-insensitive. m makes ^ and $ match line boundaries. s lets . match newlines. u enables Unicode mode. y makes the regex sticky to a specific position.
- Can I see capture group values?
- Yes. Hover over any match to see numbered and named capture groups. In replace mode, $1, $2, and ${name} substitute the captured text into the output.
- Why is my regex slow on this input?
- Usually catastrophic backtracking — nested quantifiers like (a+)+ can blow up exponentially on certain inputs. Toova flags suspicious patterns with a warning before they hang the page.
- Is my regex sent to any server?
- No. Evaluation runs entirely in your browser. The pattern and test text never leave the page, and there is no logging of either.