Syntax Updated November 2026

Anchors ^ and $

^ matches the start of the string and $ the end, so ^abc$ matches only the exact string abc. With the m (multiline) flag they match at the start and end of each line instead. Anchors match positions, not characters, and consume nothing. \b is the related word-boundary anchor.

Syntax

/^pattern$/      /^pattern$/m  (per line)      Python and PCRE: \A and \Z for absolute start and end

Examples

["cat", "concat", "cats"].map(s => /^cat$/.test(s))

Result: [true, false, false]

"ERROR a\nINFO b\nERROR c".match(/^ERROR.*$/gm)

Result: ["ERROR a", "ERROR c"]

With m, ^ and $ work per line.

"ERROR a\nINFO b".match(/^ERROR.*$/g)

Result: null

Without m, $ means end of the whole input and the dot cannot cross the newline.

"price: 100 USD".replace(/\s*USD$/, "")

Result: "price: 100"

Remove a suffix only when it is at the end.

Common mistakes

Expecting ^ and $ to work per line without the m flag.
Writing ^cat|dog$ when you mean ^(?:cat|dog)$; alternation binds loosest, so the anchors apply to only one side each.
Using ^ inside brackets, where [^...] means a negated class, not start of string.
Assuming $ ignores a trailing newline: in JavaScript it does not (abc\n fails ^abc$), while Python and PCRE let $ match before a final newline.

Practice Anchors ^ and $

These drills check your answer on live data, free, no account needed.

Anchors: lines that start with ERRORA match anywhere counts, so anchor the pattern yourself. Match lines that begin with the word ERROR in capitals.
Alternation with anchorsA match anywhere counts, so anchor it yourself. Match lines that are exactly yes or exactly no.
Multiline flag: TODO linesEach test is a block of several lines. Capture the text after TODO: on every line that starts with TODO: (TODO, colon, space).

Questions

What does ^ mean in regex?

Outside brackets it anchors the match to the start of the string, or the start of a line with the m flag. Inside brackets as the first character it negates the class.

What is the difference between $ and \Z?

In Python, $ matches at the end of the string and also just before a trailing newline; \Z matches only at the absolute end. JavaScript has no \Z and its $ is already absolute without the m flag.

How do I match an entire line?

Use ^...$ with the m flag: /^ERROR.*$/gm returns every line that starts with ERROR. Add the s flag only if you want the dot to cross lines.

Word boundary \bWhat \b matches, how to find or replace whole words only, what \B does, and why \b fails next to punctuation, in string-built regexes and with Unicode text.
Regex flagsWhat each JavaScript regex flag does (case-insensitive, global, multiline, dotAll, unicode, sticky), how to set them, and the lastIndex trap with g and test.
Alternation |How the pipe works, why ^cat|dog$ does not do what it looks like, how to group alternatives, and why option order matters when one is a prefix of another.
Escaping special charactersThe regex metacharacters that must be escaped, how to match a literal dot, dollar, plus or slash, what changes inside brackets, and how to escape user input.