Free online regex tester — JavaScript, Go, bash, sed, Perl & C#
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About Free online regex tester — JavaScript, Go, bash, sed, Perl & C#
Use this page as a general-purpose regex tester online, with a flavor picker aimed at the same long-tail queries people type for csharp regex tester, perl regex tester, bash regex tester, go regex tester, golang regex tester, sed regex tester, and go or golang regex test. Matching always runs in your browser using the JavaScript RegExp engine; when you choose Go / Golang (RE2) or Perl-style, we surface compatibility warnings (for example unsupported backreferences or lookaround in Go RE2, or Perl-only escapes) before you paste a pattern into production code.
A private regex101 alternative
Unlike regex101, which sends every pattern and test string to its backend servers, AllOneTools Regex Tester runs entirely in your browser using the native JavaScript engine. Your patterns, test strings, and sensitive data like API keys, log lines, or email addresses never leave your device. It is the privacy-first choice for developers testing regex against production data.
Key Features
- Flavor guide: JavaScript, Go / Golang (RE2), C#, Perl / PCRE-style, bash / grep ERE, GNU sed -E
- RE2 checks for golang: flags unsupported lookahead and backreferences common in JS/Perl
- Perl-oriented hints for \K, \R, and recursive (?R) patterns that JavaScript does not support
- One-click “load sample” per flavor for quick golang regex test or sed regex tester workflows
- Live match highlighting as you type
- Toggle all six JavaScript regex flags (g, i, m, s, u, y)
- Inspect every capture group per match
- Replacement preview with $1, $2 and named groups
- Runs entirely in your browser — no backend
Use Cases
- Golang regex test before shipping: confirm patterns are RE2-safe (no lookaround or backrefs)
- Bash regex tester workflow: prototype grep -E / egrep patterns then paste into scripts
- Sed regex tester workflow: try GNU sed -E style patterns before editing files in place
- Perl test regex and regex perl tester flows: spot PCRE-only escapes early
- C# regex sanity check for patterns you will move into System.Text.RegularExpressions
- Validate emails, keys, and log lines for APIs and CLIs
Pro Tips
- Pick your target flavor first — Go RE2 and JavaScript disagree on lookaround and \1 backrefs.
- For sed, prefer thinking in GNU sed -E (ERE); default BRE needs different escaping.
- For bash, treat patterns like extended regex from grep -E; test multiline with the m flag here.
- Use the “u” flag when you rely on Unicode property escapes like \p{L}.
- Use ^ and $ with the “m” flag for per-line matching in multiline logs.
Frequently Asked Questions
Is this a dedicated golang regex tester?
You can use it as one: choose “Go / Golang (RE2)” and we warn when patterns use lookahead, lookbehind, or backreferences — features JavaScript allows but Go’s RE2 engine rejects. Execution is still JavaScript; validate critical paths with a tiny Go snippet.
Does the bash regex tester mode run Bash?
No shell is started. Bash / grep ERE mode explains that egrep / grep -E style regex is closer to this tester than legacy quoting rules; patterns are evaluated with JavaScript RegExp.
How is sed regex tester mode different?
GNU sed -E (ERE) removes most BRE backslash clutter for +, ?, |, and groups. This page still uses the JS engine; the mode documents that gap so you are not surprised when moving patterns into sed -E scripts.
Can I use this as a perl regex tester?
Yes for prototyping: we flag Perl-only constructs such as \K, \R, and recursive (?R) that will not work in the browser. Final Perl behavior should always be checked with perl or pcretest.
What about C# / csharp regex tester expectations?
Many patterns are compatible with System.Text.RegularExpressions, but .NET adds its own features (balancing groups, different timeout defaults). Treat highlights here as a fast first pass, then confirm in a C# console.
Are my patterns and test data sent anywhere?
No. Compilation, matching, and replacement run locally in your tab using the built-in JavaScript regex engine.