Which named-group syntaxes are translated?

JavaScript's (? ...) becomes Python's (?P ...), and JS \\k backreferences become Python (?P=name). Going the other direction reverses the rewrite.

Why does it warn about \\A and \\Z?

Python re supports \\A (string start) and \\Z (string end) anchors that JavaScript lacks. The converter surfaces a warning so you can map them to ^ and $ with appropriate flag changes.

Are inline flags like (?i) handled?

Python supports (?i), (?m), (?s) at the start of a pattern; JavaScript does not. The converter strips them and tells you to pass the equivalent flag to the RegExp constructor instead.

Does conversion send my pattern to a server?

No. Conversion is a local string transform — patterns never leave the browser.

javascript · python re · two-way · local

Translate regex between JavaScript and Python

Convert (?<name>) ↔ (?P<name>), backreferences, and inline flags in both directions. Warnings flag Python-only anchors like \\A / \\Z. Runs in your browser.

JS ↔ Python Regex Converter

Direction

JavaScript regex

Python re pattern

^(?P<year>\d{4})-(?P<month>\d{2})$

Conversions & warnings (3)

convert(?<name>) → (?P<name>)
infoLookbehinds need fixed width in Python < 3.7 — use the regex module for variable-width.
infoPython supports inline flags (?i) and the verbose (?x) mode JS lacks.

Quick Start

How to convert between JavaScript and Python regex

Paste your pattern, pick the direction, and the converter rewrites named groups and backreferences for the target engine.

01
Pick direction
JS → Python or Python → JS. Placeholders update to match the source flavour.
Patterns are parsed with 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.
patternECMAScriptliteralregex
input · literaldirection · regex
```
JS -> Python
```
loaded · ECMAScriptPCRE · ready
02
Paste regex
Drop in a regex. (?<name>...) ↔ (?P<name>...) and \k<name> ↔ (?P=name) translate automatically.
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 · optionsregex · flags
```
(?<year>\d{4})
```
flags applied · liveECMA · live
03
Review notes
A list of conversions and warnings appears beside the output. Python-only \A and \Z are flagged.
Conversions translate flavour-specific constructs (lookarounds, named groups, character classes) — the converter flags anything that has no equivalent in the target engine.
convertflavourPCRE · RE2diff
run · outputdiff · converted
```
(?P<year>\d{4})
```
matches · livediff · ready
04
Copy and ship
One-click copy lands the result in your editor.
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’t parsers

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

Use Cases

When JS regex meets Python

Sharing validators, parsers, and scrapers between front-end and back-end.

Reuse validators

Lift a JS form regex into a Django backend. 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

Data pipelines

Move a regex from Node.js to a Python ETL job. 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

Scraping toolkit

Translate a Cheerio-side regex into BeautifulSoup country. 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

Doc parity

Keep API regex docs in sync across JS and Python clients. 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

Migrate scripts

Port shell-glued regexes from Node to Python during a refactor. 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

Cross-team review

Show Python devs the same regex they write in JS — and vice versa. 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

Why two named-group forms?

JavaScript uses (?<name>...) while Python's re module uses (?P<name>...). The converter rewrites both directions.

What about \k<name>?

JS backreferences (\k<name>) become Python's (?P=name) form when going to Python, and vice versa.

Are inline flags converted?

Python inline flags like (?i) are stripped when going to JS; flags belong on the regex literal in JS instead.

Are \A and \Z handled?

Python's \A and \Z have no JS equivalent — the converter warns and leaves the construct as-is.

Is anything sent to a server?

No — conversion happens entirely in your browser.

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