Regex Tester

How Regex Testing Works

Toolkiya compiles your regular expression using the browser's native RegExp engine and runs it against the test string in real time as you type. Matches are highlighted inline, capture groups are listed in a side panel, and named groups are labeled by their name. You can toggle flags — g, i, m, s, u, y — and watch the match set change immediately.

For every match, the tool shows the matched substring, its start and end index, and each capture group's value. A replace mode lets you preview the result of String.prototype.replace with backreferences ($1, $2, named groups). Because the engine is the same one your JavaScript runtime uses, what you see in the tester is exactly what your code will see in production.

When to Use a Regex Tester

Building a pattern to validate emails, phone numbers, or custom IDs before shipping it into form validation. Debugging a regex copied from Stack Overflow that almost works. Extracting fields from log lines, CSV cells, or scraped HTML. Writing search-and-replace patterns for a code refactor across a large codebase. Learning regex syntax interactively without spinning up a REPL.

Why Test Regex in Toolkiya

Your test strings often contain real production data — log snippets, customer emails, internal URLs. Pasting that into an online tester means it sits in someone else's request logs. Toolkiya runs the regex engine entirely in your browser, so neither the pattern nor the test string ever leaves your tab.

There is no signup, no rate limit, no character cap on the test string, and no daily quota. You can iterate on a regex for hours and burn through thousands of test inputs without anyone watching over your shoulder.

Tips for Writing Better Regex

Prefer non-greedy quantifiers (.*?) when matching between delimiters to avoid runaway matches. Anchor with ^ and $ when validating whole strings rather than substring matching. Use named capture groups (?<name>...) for readability when you have more than two groups. Watch out for catastrophic backtracking patterns — nested quantifiers on the same character class are the usual culprit.