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js · pcre · python · java · .net · go · ruby · rust

See which regex engines accept your pattern

Detect flavour-specific syntax in your regex and check the OK/PARTIAL/NO status across eight engines. Runs locally.

Regex Flavour Detector
Features
4
detected
OK flavours
1
of 8
Incompatible
7
engines
Total checks
18
syntax tests
input · regex pattern
output · compatibility matrix
Compatibility matrix
JS
NO
PCRE
OK
Python
NO
Java
NO
.NET
NO
Go
NO
Ruby
NO
Rust
NO
Features detected (4)
Named group (?P<name>)
Possessive quantifier (*+, ++)
Unicode property \p{...}
Literal block \Q...\E
Per-flavour notes
JS
  • Named group (?P<name>): Use (?<name>)
  • Possessive quantifier (*+, ++) not supported
  • Unicode property \p{...}: Needs /u flag
  • Literal block \Q...\E not supported
Python
  • Possessive quantifier (*+, ++): Supported in Python 3.11+
  • Unicode property \p{...}: Use the regex 3rd-party module
  • Literal block \Q...\E not supported
Java
  • Named group (?P<name>): Use (?<name>)
.NET
  • Named group (?P<name>): Use (?<name>)
  • Possessive quantifier (*+, ++) not supported
  • Literal block \Q...\E not supported
Go
  • Possessive quantifier (*+, ++) not supported
  • Literal block \Q...\E not supported
Ruby
  • Named group (?P<name>): Use (?<name>)
  • Literal block \Q...\E not supported
Rust
  • Possessive quantifier (*+, ++) not supported
  • Literal block \Q...\E not supported
Quick Start

How to check regex flavour compatibility

Paste a regex and see which engines accept it as-is, which need rewrites, and which can't run it at all.

  1. 01

    Paste pattern

    Drop any regex in — JavaScript syntax, PCRE syntax, or Python syntax all welcome.

    Patterns compile through the JavaScript RegExp constructor, so syntax errors surface immediately and engine quirks like Unicode property escapes (\p{L}) work when the u flag is on.

    patternECMAScriptliterallive
    input · literalregex · regex
    (?P<id>\d+)\p{L}+
    loaded · ECMAScriptPCRE · ready
  2. 02

    Read the matrix

    Eight flavours (JS, PCRE, Python, Java, .NET, Go, Ruby, Rust) tagged OK, PARTIAL, or NO.

    Each flag character mirrors the ECMAScript literal: g enables iteration, i folds case, m anchors per line, s lets . match newlines, u unlocks proper Unicode, y is sticky, and d emits indices.

    flagsoptionsg · i · mlive
    config · optionsmatrix · flags
    JS no Python ok
    flags applied · liveECMA · live
  3. 03

    Inspect per-flavour notes

    PARTIAL and NO results explain why and suggest a rewrite where possible.

    Watch for catastrophic backtracking on nested quantifiers — a common ReDoS source. The tool caps match counts to keep the page responsive on pathological patterns.

    matchgroupshighlightReDoS-safe
    run · outputnotes · matches
    Python: Use (?P=name)
    matches · livegroups · live
  4. 04

    Copy or export

    Grab the output as JSON, CSV, or plain text — ready for your editor or pipeline.

    Copy writes via navigator.clipboard.writeText; downloads use a Blob and object URL, so nothing transits the network and the output is byte-identical to what you see on screen.

    copyexportclipboardblob
    export · exportedready · saved
    Copied
    ready to shipsuccess
Pro tips

Regex patterns that don't melt down

Use named groups

(?<year>\d{4}) reads better than $1 and survives reordering. Supported in ECMAScript 2018+.

Anchor strictly

Use ^/$ with the m flag when matching whole lines. Without anchors, partial matches sneak through.

Avoid catastrophic backtracking

Nested quantifiers like (a+)+ can explode. Run patterns through ReDoS Detector first.

Escape every literal

Backslash any meta character you want literally: \.\$\^\*\+\?\(\)\[\]\{\}\|\\.

Test edge cases

Empty string, single character, unicode, the maximum length you expect — write fixtures for each.

Patterns aren&rsquo;t parsers

Don’t parse HTML, JSON, or balanced parens with regex. Use a proper parser when the grammar is recursive.

Related toolsRegex Flavour MatrixJs Python ConverterJs Pcre ConverterRegex ExplainerRegex TesterRegex Cheatsheet
Use Cases

When to check flavours

Audit a regex before shipping it cross-stack.

Port across stacks

See which flavours can run a regex unchanged. Compiles through the JavaScript RegExp constructor — engine quirks (Unicode property escapes, sticky matching, named groups) work when their flags are on. Error messages cite the exact position of any syntax issue.

ReDoS-safe

Pick a tool

Choose Go's RE2 or Python's re based on regex needs. Pairs with the ReDoS detector to catch catastrophic backtracking before you deploy. A pattern that handles 1k-character input fine can become a denial-of-service vector on attacker-controlled 1M-character input.

ECMA-compliant

Document constraints

Spell out flavour requirements in a spec. Output exports as JavaScript, Python re, Java util.regex, .NET System.Text.RegularExpressions, PCRE, and POSIX — language quirks are highlighted on conversion so you don't ship a JS-only pattern to a Go service.

spec-grade

Catch portability bugs

Spot Java-only features used in a JS codebase. Capture groups (named or numbered) round-trip cleanly into replacement strings, JSON output, or CSV extraction without re-typing. Backreferences ($1, ${name}) preserve semantics across languages.

cross-engine

Teach flavour quirks

Show students which features vary between engines. Test against edge cases — empty input, single character, max length, multibyte boundaries — to catch off-by-one and zero-length match bugs before they reach production.

test-ready

Migration audit

Sweep a codebase before swapping regex engines. All matching runs client-side so secret patterns never leave the browser. Useful when the pattern itself is sensitive (PII regexes, internal data formats, security filters).

production-ready
FAQ

Frequently asked questions

Heuristic — based on common engine documentation. Edge cases (especially around Unicode and lookbehinds) may differ between engine versions.
The feature works but needs a flag or a slightly different syntax. The notes panel spells out the change.
Yes — the toolbar Copy button grabs a plain-text version including notes.
PHP uses PCRE, so the PCRE column covers it.
No. The tool runs entirely in your browser — your pattern and sample text never leave the page.
Suggest a tool

Something missing?

Tell us what you need. We ship the top requests every two weeks.

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