Awesome Regex curates the best regular expression tools, tutorials,
libraries, and other resources, covering all major regex flavors.
Regular
expressions (regex or regexp) are a powerful and concise way to
search, parse, and process text. They’re built into many programming
languages, text editors, IDEs, database engines, word processors, and
other tools.
Contributions are welcome. Add links through pull requests (guidelines).
📖 Glossary
A brief glossary of regular expression terms as used in this
list.
Regex engine: Software that interprets and executes
regular expressions, either built into a programming language or as a
standalone library.
Regex flavor: A unique set of regex syntax and
behavior. Basic syntax is typically shared across flavors, but more
advanced features often vary, sometimes in subtle or incompatible ways.
A flavor might be shared across multiple implementations or programming
languages.
Ex: The “JavaScript” flavor is defined by the ECMAScript spec;
implemented by multiple engines (V8, etc.).
Ex: The “PCRE” flavor is the PCRE2 library, used by numerous
programming languages and tools.
Ex: Ruby swapped its regex implementation twice from version 1.8 →
1.9 → 2.0, so each used a distinct flavor. The Ruby 2.0+ flavor is
referred to here as either “Ruby” or “Onigmo” (the underlying regex
library).
Non-backtracking engine: A regex implementation
that uses a non-backtracking algorithm and runs in linear time. This
rules out worst case performance from superlinear backtracking, but it’s
slower with some patterns and precludes some useful features like
backreferences.
Featured resource
Regex+ is a
lightweight JavaScript library for more readable, high-performance,
native JavaScript regexes with powerful features including free spacing,
atomic groups, possessive quantifiers, subroutines, subroutine
definition groups, and context-aware interpolation.
Regex DB - Solutions include basic
descriptions and examples of matching and non-matching text.
⚠️ Word of warning
Many regexes found online are low quality. It’s risky to use regexes you
don’t fully understand in code, since they might have false
positives/negatives, be vulnerable to performance problems with certain
target strings, or assume a different regex flavor.
JavaScript regex libraries
Open source JavaScript libraries for advanced regex use and
processing.
Alternative regex
builders and engines
Regex+ - A template
tag for extended, readable, high-performance JavaScript regexes.
Oniguruma-To-ES
- Convert Oniguruma patterns to native JavaScript regexes.
XRegExp [home] - Extended regex syntax,
flags, and utils; useful for backcompat.
The history of improvements to regular expressions in the
JavaScript standard.
Starting with ES2018, includes links to the TC39 proposals where
features were developed and discussed.
ES3 (1999) introduced regular expressions.
ES5 (2009) fixed unintuitive behavior by creating a new object every
time regex literals are evaluated [explainer],
and allowed regex literals to use unescaped forward slashes within
character classes (/[/]/).
Flag y (sticky), which anchors matches to
lastIndex.
Flag u (unicode) [explainer]
[2016 spec
fix], which adds Unicode code point escapes via
\u{…}, strict errors (for unreserved escapes, octal
escapes, quantified lookahead, and unescaped special characters in some
contexts), Unicode case-folding for flag i, and code point
matching (with impact on quantifiers, character classes, ranges, and
built-in sets).
Getter RegExp.prototype.flags, the ability to copy a
regex using RegExp (optionally with new flags), and support
for subclassing RegExp (along with
RegExp.prototype[Symbol.match/replace/search/split]
and RegExp[Symbol.species]).
ES2020 added string method matchAll
(which returns an iterator), plus
RegExp.prototype[Symbol.matchAll].
ES2022 added flag
d (hasIndices), which provides start/end
indices for matched substrings.
ES2024 added flag
v (unicodeSets) [explainer] as
an upgrade to flag u, which adds a set of multicharacter
“properties of strings” to \p{…}, multicharacter elements
within character classes via \p{…} and
\q{…|…}, nested character classes, set operators
[…--…] and […&&…], and different
escaping rules within character classes. It also fixes case-insensitive
matching for \p and \P within negated
[^…].
Each edition from ES2019 to ES2023 added additional Unicode properties
that can be used via \p{…} and \P{…} (see lists).
ES2021 added string method replaceAll,
although, when given a regex, the only difference from ES3’s
replace is that it throws if not using flag g.
➕ See also
Regular
Expressions Cookbook, 2nd Edition (2012) by Jan Goyvaerts and
Steven Levithan - Regex tutorial with code samples for eight programming
languages, 100+ regex recipes for practical problems, and a deep focus
on cross-flavor differences.
Mastering
Regular Expressions, 3rd Edition (2006) by Jeffrey Friedl - A
computer science classic, best for people who already know the basics.
Includes good coverage of crafting efficient regexes.
Flavors: Dedicated chapters on Java, .NET, Perl, and PHP (PCRE),
with more limited coverage of Python, Tcl, command line tools, etc.
Introducing
Regular Expressions (2012) by Michael Fitzgerald - An intro for
programmers new to regular expressions that sticks to the basics.
Shortcut URL: 
,
$40) - Best tester.
,
$3) - Bash, Emacs, grep, Java, Oniguruma, PCRE, POSIX BRE, POSIX ERE,
Ruby, sed.
