Regex Visualizer

An interactive tool for understanding regular expressions — railroad diagrams, match highlighting, and step-by-step engine simulation.

Railroad diagram — visual syntax tree of the pattern
Match highlighting — colored capture groups
Step-by-step — animate the regex engine stepping through text
Cheat sheet — toggle sidebar for quick reference
Presets — common patterns to explore

Click anywhere to start

Anchors

^Start of string/line

$End of string/line

\bWord boundary

\BNon-word boundary

Quantifiers

*0 or more (greedy)

+1 or more (greedy)

?0 or 1 (optional)

{n}Exactly n times

{n,m}Between n and m

*?Lazy (non-greedy)

Character Classes

.Any char (exc. newline)

\dDigit [0-9]

\wWord char [a-zA-Z0-9_]

\sWhitespace

\D\W\SNegated versions

[abc]Character set

[^abc]Negated set

[a-z]Character range

Groups

(abc)Capture group

(?:abc)Non-capture group

(?=...)Lookahead

(?!...)Negative lookahead

(?<name>)Named capture

\1Backreference

Alternation

a|bMatch a or b

Flags

gFind all matches

iCase insensitive

mMultiline ^ and $

sDot matches newline

Pattern

Test

literal / char class

quantifier

group

anchor

full match

group 1

group 2

group 3

Railroad Diagram

Test String — Matches

History

Match Info

Step-by-step