⌘ K
ascii tree · plain text · copy-ready

Render any regex as a copy-pasteable ASCII tree

A monospace structural view of any regex, ready to drop into PRs, chats, and commit messages.

Regex Tree Viewer
Nodes
8
incl. nested
Top-level
5
siblings
Pattern
23 B
chars
Status
valid
ok
input · pattern
//
output · ascii tree
├── [group] (
│   └── [escape] \d (×{3})
├── [literal] -
├── [group] (
│   └── [escape] \d (×{3})
├── [literal] -
└── [group] (
    └── [escape] \d (×{4})
Quick Start

How to view a regex as ASCII tree

Render a regex into a copy-pasteable ASCII tree, perfect for chat, commits, and code reviews.

  1. 01

    Paste a pattern

    Drop in any regex. The structural parser builds the AST.

    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 · literalpattern · regex
    (\d{3})-(\d{3})
    loaded · ECMAScriptPCRE · ready
  2. 02

    Read the tree

    Each node prints its type, value, and quantifier. Branches use standard box-drawing characters.

    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
    tree · optionsascii · flags
    ├── [group] (
    flags applied · liveECMA · live
  3. 03

    Copy the output

    Drop the tree into a PR, chat, or commit message — looks great in monospace.

    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
    share · outputcopy · matches
    ready
    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 VisualizerRegex ExplainerRegex TesterRegex BuilderRegex CheatsheetRegex Character Classes
Use Cases

When ASCII trees help

Shareable structural views in any tool.

Share in chat

Monospace-friendly structural view. 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

Commit messages

Document why a pattern looks the way it does. 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

Code reviews

Make complex regex reviewable. 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

Teach structure

Walk students through nesting. 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

Compare drafts

Diff two trees for refactor impact. 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

Audit captures

Confirm which groups capture. 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

Yes — indentation is proportional and box-drawing characters keep alignment consistent.
The structural parser is permissive, so even a JS-invalid pattern usually yields a sensible best-effort tree.
No — quantifiers attach to their preceding node and are printed inline as ×n notation.
It is ASCII — colour comes from your terminal or markdown viewer.
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.

Sent straight to the maintainers · no account needed
47 in queue·8 shipped this month
Request queued. Thanks!