What this calculator does
Every input on this regex tester maps to a real decision, so the output is something you can act on immediately, not a rough ballpark you'll have to double-check elsewhere.
Test regular expressions and see matches.
How to use the Regex Tester
- Enter your input.
- The result updates automatically.
- Copy or share the result.
The formula
new RegExp(pattern, flags)
Worked example
\d+ against 'abc123def' → matches '123'.
Common mistakes
- Escaping in strings
- Greedy vs lazy quantifiers
- Regex for HTML
When to use it
Use for validation, parsing, search-replace.
Pro tips for the Regex Tester
- Copy the result to paste it directly into email, Notion, or a spreadsheet cell.
- Use Print / PDF to export a clean, ad-free summary you can share with a client or advisor.
- The chart updates live — drag values up and down to build intuition for how the formula behaves.
Frequently asked questions
›Flags?
g global, i case-insensitive, m multiline, s dotAll.
›Groups?
() captures; (?:) non-capturing.
›Lookahead?
(?=...); lookbehind (?<=...).
›Named groups?
(?<name>...).
›Anchors?
^ start, $ end, \b word boundary.
›Is the Regex Tester free to use?
Yes. Every calculator on CalcPilot, including the Regex Tester, is free with no sign-up, no watermark, and no export limit.
›Can I embed the Regex Tester on my site?
Embedding isn't public yet, but you can link directly to this page — the URL is stable and shareable.
Embed this calculator
Drop the Regex Tester into your own site or blog post. Free to use — a small “Powered by CalcPilot” link is appreciated.
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