Comparison of regular expression engines

This is a comparison of regular expression engines.

Libraries
List of regular expression libraries
Name Official website Programming language Software license Used by
Boost.Regex[Note 1] Boost C++ Libraries C++ Boost Notepad++ >= 6.0.0, EmEditor
Boost.Xpressive Boost C++ Libraries C++ Boost  
DEELX RegExLab C++ Proprietary  
FREJ[Note 2] Fuzzy Regular Expressions for Java Java LGPL  
GLib/GRegex[Note 3] GLib reference manual C LGPL  
GNU regex Gnulib reference manual C LGPL GNU libc, GNU programs
GRETA Microsoft Research C++ Proprietary  
Gregex Grovf Inc. RTL, HLS Proprietary FPGA accelerated >100Gbit/s regex engine for cybersecurity, financial, e-commerce industries.
Hyperscan Intel C, x86-specific assembly (SSSE3+[1]) 3-clause BSD Rspamd
ICU International Components for Unicode C, C++[Note 4] ICU Foundation (Apple and Swift open-source versions)
Jakarta Regexp The Apache Jakarta Project Java Apache  
java.util.regex Java's User manual Java GNU GPLv2 with Classpath exception jEdit
JRegex JRegex Java BSD  
MATLAB Regular Expressions MATLAB Language Proprietary  
Oniguruma Kosako C BSD Atom, Take Command Console, Tera Term, TextMate, Sublime Text, SubEthaEdit, EmEditor and jq
Pattwo Stevesoft Java (compatible with Java 1.0) LGPL  
PCRE pcre.org C, C++[Note 5] BSD Apache HTTP Server, Nginx, BBEdit, Edbrowse, Julia, HHVM, Notepad++ < 6.0.0, PHP, Delphi, R, Exim SWI-Prolog
Qt/QRegExp Digia C++ Qt GNU GPL v. 3.0,

Qt GNU LGPL v. 2.1, Qt Commercial

 Kate, Kile
regex - Henry Spencer's regular expression libraries ArgList C BSD  
RE2 RE2 C++ BSD Go, Google Sheets, Gmail, G Suite
Henry Spencer's Advanced Regular Expressions Tcl C BSD  
RGX RGX C++ based component library P6R  
RXP Titan IC RTL Proprietary hardware-accelerated search acceleration using RegEx available for ASIC, FPGA and cloud. Enables massively parallel content processing at ultra-high speeds.
SubReg Matt Bucknall C MIT  
TPerlRegEx TPerlRegEx VCL Component Object Pascal MPLv1.1  
TRE[Note 2] Ville Laurikari C BSD musl
TRegExpr TRegExpr, documentation,

(RegExp Studio)

 Object Pascal Dual-license: freeware, or LGPL with static linking exception Total Commander
Wolfram Language (Mathematica) Wolfram Language Documentation Center Wolfram Language Proprietary Mathematica, the Wolfram Development Platform
XRegExp XRegExp JavaScript MIT  
  1. Formerly called Regex++.
  2. One of fuzzy regular expression engines.
  3. Included since version 2.13.0.
  4. ICU4J, the Java version, does not support regular expressions.
  5. C++ bindings were developed by Google and became officially part of PCRE in 2006.

Languages
List of languages and frameworks including regular expression support
Language Official website Software license Remarks
ActionScript 3 ActionScript Technology Center Free
APL (APLX, Dyalog, GNU) APL Wiki Licensed by the respective implementation ⎕SS (PCRE), ⎕R/⎕S (PCRE), ⎕SS (PCRE2), respectively
C++11 (C++) C++ standards website Licensed by the respective implementation Since ISO14822:2011(e), similar to ECMAScript on default (Grammar Description)
D D Boost Software License[Note 1]
Free Pascal (Object Pascal) freepascal.org LGPL with static linking exception Free Pascal 2.6+ ships with TRegExpr from Sorokin and two other regular expression libraries; See wiki.lazarus.freepascal.org/Regexpr.
Go Golang.org BSD-style
Haskell Haskell.org BSD3 Omitted in the language report, and in GHC's Hierarchical Libraries
Java Java GNU General Public License REs are written as strings in source code: all backslashes must be doubled, harming readability.
JavaScript (ECMAScript) ECMA-262 BSD3 Limited but REs are first-class citizens of the language with a specific /.../mod syntax.
Julia JuliaLang.org MIT License REs are part of the language core library using PCRE built-in and an optional wrapper for (C code) ICU is available.
Lua Lua.org MIT License Uses simplified, limited dialect; can be bound to more powerful library, like PCRE or an alternative parser like LPeg.
Mathematica Wolfram Proprietary
.NET MSDN MIT License[Note 2][Note 3]
Nim nim-lang.org MIT License Standard library includes PCRE-based re and nre modules, as well as various alternatives (ex. strutils, pegs (Parsing Expression Grammar matching), strscans, parseutils, etc.).
OCaml Caml LGPL As of 2010, the standard module is generally regarded as deprecated;[2] often recommended libraries are pcre (with full support for PCRE) and re (which is not as complete but claims better performance and provides frontends to popular syntaxes: PCRE, Perl, Posix, Emacs, shell globbing).
Perl Perl.com Artistic License, or GNU General Public License Full, central part of the language
PHP PHP.net PHP License Has two implementations, with PCRE being the more efficient in speed, functions
POSIX C (C) POSIX.1 web publication Licensed by the respective implementation Supports POSIX BRE and ERE syntax
Python python.org Python Software Foundation License Python has two major implementations, the built in re and the regex library.
Ruby ruby-doc.org GNU Library General Public License Ruby 1.8, Ruby 1.9, and Ruby 2.0 and later versions use different engines; Ruby 1.9 integrates Oniguruma, Ruby 2.0 and later integrate Onigmo, a fork from Oniguruma.
Rust docs.rs MIT License The primary regex crate does not allow look-around expressions. There is an Oniguruma binding called onig that does.
SAP ABAP SAP.com Proprietary
Tcl tcl.tk Tcl/Tk License
(BSD-style)		 Tcl library doubles as a regular expression library.
Wolfram Language Wolfram Research Proprietary: usable for free on a limited scale on the Wolfram Development platform
XML Schema W3C Licensed by the respective implementation
XPath 3/XQuery W3C Licensed by the respective implementation
  1. "STD.regex - D Programming Language - Digital Mars".
  2. "Dotnet/Corefx". GitHub. 16 February 2022.
  3. "Dotnet/Corefx". GitHub. 16 February 2022.

Language features

NOTE: An application using a library for regular expression support does not necessarily support the full set of features of the library, e.g., GNU grep uses PCRE, but supports no lookahead, though PCRE does.

Part 1
Language feature comparison (part 1)
"+" quantifier Negated character classes Non-greedy quantifiers
[Note 1]		 Shy groups
[Note 2]		 Recursion Look-ahead Look-behind Backreferences
[Note 3]		 >9 indexable captures
Boost.Regex Yes Yes Yes Yes Yes[Note 4] Yes Yes Yes Yes
Boost.Xpressive Yes Yes Yes Yes Yes[Note 5] Yes Yes Yes Yes
CL-PPCRE Yes Yes Yes Yes No Yes Yes Yes Yes
EmEditor Yes Yes Yes Yes No Yes Yes Yes No
FREJ No[Note 6] No Some[Note 6] Yes No No No Yes Yes
GLib/GRegex Yes Yes Yes Yes Yes Yes Yes Yes Yes
GNU grep Yes Yes Yes Yes No Yes Yes Yes —
Haskell Yes Yes Yes Yes No Yes Yes Yes Yes
RXP Yes Yes Yes Yes No No No Yes Yes
ICU Regex Yes Yes Yes Yes No Yes Yes Yes Yes
Java Yes Yes Yes Yes No Yes Yes Yes Yes
JavaScript (ECMAScript) Yes Yes Yes Yes No Yes Yes[Note 7] Yes Yes
JGsoft Yes Yes Yes Yes No Yes Yes Yes Yes
Lua Yes Yes Some[Note 8] No No No No Yes No
.NET Yes Yes Yes Yes No Yes Yes Yes Yes
OCaml Yes Yes No No No No No Yes No
PCRE Yes Yes Yes Yes Yes Yes Yes Yes Yes
Perl Yes Yes Yes Yes Yes Yes Yes Yes Yes
PHP Yes Yes Yes Yes Yes Yes Yes Yes Yes
Python Yes Yes Yes Yes Yes[Note 9] Yes Yes Yes Yes
Qt/QRegExp Yes Yes Yes Yes No Yes No Yes Yes
RE2 Yes Yes Yes Yes No No No No Yes
Ruby, Onigmo Yes Yes Yes Yes Yes Yes Yes Yes Yes
TRE Yes Yes Yes Yes No No No Yes No
Vim Yes Yes Yes Yes No Yes Yes Yes No
RGX Yes Yes Yes Yes No Yes Yes Yes Yes
Tcl Yes Yes Yes Yes No Yes Yes Yes Yes
TRegExpr Yes ? Yes ? ? ? ? ? ?
XML Schema Yes Yes No — No No No No —
XPath 3/XQuery Yes Yes Yes Yes No No No Yes Yes
XRegExp Yes Yes Yes Yes No Yes Yes[Note 7] Yes Yes
  1. Non-greedy quantifiers match as few characters as possible, instead of the default as many. Note that many older, pre-POSIX engines were non-greedy and didn't have greedy quantifiers at all.
  2. Shy groups, also called non-capturing groups cannot be referred to with backreferences; non-capturing groups are used to speed up matching where the group's content does not need to be accessed later.
  3. Backreferences enable referring to previously matched groups in later parts of the regex and/or replacement string (where applicable). For instance, ([ab]+)\1 matches "abab" but not "abaab".
  4. "Perl Regular Expression Syntax - 1.47.0".
  5. "User's Guide - 1.47.0".
  6. FREJ have no repetitive quantifiers, but have "optional" element which behaves similar to simple "?" quantifier.
  7. As of ES2018
  8. Lua's only non-greedy quantifier is -, which is a non-greedy version of *. It does not have non-greedy versions of + or ?; in the former case, the non-greedy effect can be achieved by repeating the token followed by -, but in the latter case, there is no equivalent.
  9. Supported by the optional regex library only.

Part 2
Language feature comparison (part 2)
Directives
[Note 1]		 Conditionals Atomic groups
[Note 2]		 Named capture
[Note 3]		 Comments Embedded code Unicode property support [3] Balancing groups
[Note 4]		 Variable-length look-behinds
[Note 5]
Boost.Regex Yes Yes Yes Yes Yes No Some[Note 6] No No
Boost.Xpressive Yes No Yes Yes Yes No No No No
CL-PPCRE Yes Yes Yes Yes Yes Yes Some[Note 6] No No
EmEditor Yes Yes ? ? Yes No ? No No
FREJ No No Yes Yes Yes No ? No No
GLib/GRegex Yes Yes Yes Yes Yes No Some[Note 6] No No
GNU grep Yes Yes ? Yes Yes No No No No
Haskell ? ? ? ? ? No No No No
RXP Yes Yes No Yes Yes No No No No
ICU Regex Yes No Yes Yes[Note 7] Yes No Yes No No
Java Yes No Yes Yes[Note 8] Yes No Some[Note 6] No No
JavaScript (ECMAScript) No No No Yes No No Some[Note 6][Note 9][4] No Yes
JGsoft Yes Yes Yes Yes Yes No Some[Note 6] No Yes
Lua No No No No No No No No No
.NET Yes Yes Yes Yes Yes No Some[Note 6] Yes Yes
OCaml No No No No No No No No No
PCRE Yes Yes Yes Yes Yes Yes Yes No No
Perl Yes Yes Yes Yes Yes Yes Yes No No[Note 10]
PHP Yes Yes Yes Yes Yes No No No No
Python Yes Yes Yes[Note 11] Yes Yes No Yes[Note 12] No Yes[Note 13]
Qt/QRegExp No No No No No No No No No
RE2 Yes No  ? Yes No No Some[Note 6] No No
Ruby, Onigmo Yes Yes Yes Yes Yes No Some[Note 6] No No
Tcl Yes No Yes No Yes No Yes No No
TRE Yes No No No Yes No ? No No
Vim Yes No Yes No No No No No Yes
RGX Yes Yes Yes Yes Yes No Yes No No
XML Schema No No No No No No Yes No No
XPath 3/XQuery No No No No No No Yes No No
XRegExp Leading only No No Yes Yes No Yes No Yes
  1. Also known as flags modifiers, modes modifiers or option letters. Example pattern: "(?i:test)".
  2. Also called independent sub-expressions.
  3. Similar to back references, but with names instead of indices.
  4. Special feature allowing to match balanced constructs without recursion.
  5. Refers to the possibility of including quantifiers in look-behinds, thus making their length unpredictable.
  6. Unicode property support may be incomplete (products are continuously updated!). All will be incomplete when a new Unicode revision is released until they are updated to comply.
  7. Available as of ICU55.
  8. Available as of JDK7.
  9. The support and range of properties is dependent on implementation.
  10. Experimental support added in v5.29.9.
  11. Supported by Python v3.11 and later, and the optional regex library only.
  12. May only be available in the regex library when used with Python versions after 3.3.
  13. Supported by the optional regex library only.

API features
API feature comparison
Native UTF-16 support[Note 1] Native UTF-8 support[Note 1] Multi-line matching Partial match[Note 2]
Boost.Regex No No Yes Yes
GLib/GRegex Yes Yes Yes Yes
RXP Yes Yes No Yes
ICU Regex Yes No Yes ?
Java Yes[Note 3] Yes[Note 3] Yes Yes
.NET No[Note 4] Yes Yes ?
PCRE Yes[Note 5] Yes Yes Yes
Qt/QRegExp Yes No No ?
Tcl Yes Yes[Note 6] Yes ?
TRE Yes Yes Yes ?
RGX No No Yes ?
wxWidgets::wxRegEx[Note 7] Yes Yes Yes ?
XRegExp Yes Yes Yes No
  1. Means the format can be used internally without explicit conversion.
  2. Partial match of the whole regular expression. For example the pattern ".*END$" will match any string partially, but only strings ending with END fully..
  3. Supports Unicode 15.0 standard from 2023..
  4. Implementation uses original UCS-2 support/features, so it only recognizes 64K chars total (vs UTF-16's 1,112,064 characters). A Microsoft developer-representative answered a bug report on this as "will not fix" in 2010..
  5. Since version 8.30.
  6. Tcl includes facilities to convert to and from UTF-8.
  7. wxRegEx uses any system supplied POSIX library or if not available and for Unicode mode uses Henry Spencer's library.

See also

References
  1. "Getting Started – Hyperscan 5.4.0 documentation".
  2. "Regex - Regular Expressions in OCaml".
  3. "UTS #18: Unicode Regular Expressions".
  4. "ECMA-262, 9th edition, June 2018 ECMAScript® 2018 Language Specification". www.ecma-international.org. Retrieved 4 August 2020.
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