This is a comparison of regular expression engines.
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 >100 Gbit/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 Archived 2013-12-12 at the Wayback Machine | C++ | Qt GNU GPL v. 3.0, | 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, | 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 |
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 [update] , 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 |
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.
"+" 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 | Yes [3] | 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 |
-
, 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.Directives [Note 1] | Conditionals | Atomic groups [Note 2] | Named capture [Note 3] | Comments | Embedded code | Unicode property support [4] | 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] [5] | 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 |
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 | Yes [Note 6] |
Qt/QRegularExpression | Yes | Yes | Yes | Yes |
Tcl | Yes | Yes [Note 7] | Yes | ? |
TRE | Yes | Yes | Yes | ? |
RGX | No | No | Yes | ? |
wxWidgets::wxRegEx [Note 8] | Yes | Yes | Yes | ? |
XRegExp | Yes | Yes | Yes | No |
A regular expression, sometimes referred to as rational expression, is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation. Regular expression techniques are developed in theoretical computer science and formal language theory.
UTF-8 is a variable-length character encoding standard used for electronic communication. Defined by the Unicode Standard, the name is derived from Unicode Transformation Format – 8-bit.
UTF-16 (16-bit Unicode Transformation Format) is a character encoding capable of encoding all 1,112,064 valid code points of Unicode (in fact this number of code points is dictated by the design of UTF-16). The encoding is variable-length, as code points are encoded with one or two 16-bit code units. UTF-16 arose from an earlier obsolete fixed-width 16-bit encoding now known as "UCS-2" (for 2-byte Universal Character Set), once it became clear that more than 216 (65,536) code points were needed, including most emoji and important CJK characters such as for personal and place names.
A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine.
JScript is Microsoft's legacy dialect of the ECMAScript standard that is used in Microsoft's Internet Explorer web browser.
In computer programming, glob patterns specify sets of filenames with wildcard characters. For example, the Unix Bash shell command mv *.txttextfiles/
moves all files with names ending in .txt
from the current directory to the directory textfiles
. Here, *
is a wildcard and *.txt
is a glob pattern. The wildcard *
stands for "any string of any length including empty, but excluding the path separator characters ".
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International Components for Unicode (ICU) is an open-source project of mature C/C++ and Java libraries for Unicode support, software internationalization, and software globalization. ICU is widely portable to many operating systems and environments. It gives applications the same results on all platforms and between C, C++, and Java software. The ICU project is a technical committee of the Unicode Consortium and sponsored, supported, and used by IBM and many other companies. ICU has been included as a standard component with Microsoft Windows since Windows 10 version 1703.
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Perl Compatible Regular Expressions (PCRE) is a library written in C, which implements a regular expression engine, inspired by the capabilities of the Perl programming language. Philip Hazel started writing PCRE in summer 1997. PCRE's syntax is much more powerful and flexible than either of the POSIX regular expression flavors and than that of many other regular-expression libraries.
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BSON is a computer data interchange format. The name "BSON" is based on the term JSON and stands for "Binary JSON". It is a binary form for representing simple or complex data structures including associative arrays, integer indexed arrays, and a suite of fundamental scalar types. BSON originated in 2009 at MongoDB. Several scalar data types are of specific interest to MongoDB and the format is used both as a data storage and network transfer format for the MongoDB database, but it can be used independently outside of MongoDB. Implementations are available in a variety of languages such as C, C++, C#, D, Delphi, Erlang, Go, Haskell, Java, JavaScript, Julia, Lua, OCaml, Perl, PHP, Python, Ruby, Rust, Scala, Smalltalk, and Swift.
A regular expression denial of service (ReDoS) is an algorithmic complexity attack that produces a denial-of-service by providing a regular expression and/or an input that takes a long time to evaluate. The attack exploits the fact that many regular expression implementations have super-linear worst-case complexity; on certain regex-input pairs, the time taken can grow polynomially or exponentially in relation to the input size. An attacker can thus cause a program to spend substantial time by providing a specially crafted regular expression and/or input. The program will then slow down or become unresponsive.
TRE is an open-source library for pattern matching in text, which works like a regular expression engine with the ability to do approximate string matching. It was developed by Ville Laurikari and is distributed under a 2-clause BSD-like license.
RE2 is a software library which implements a regular expression engine via finite-state machines using automata theory, in contrast to almost all other regular expression libraries, which use backtracking implementations. It provides a C++ interface.
musl is a C standard library intended for operating systems based on the Linux kernel, released under the MIT License. It was developed by Rich Felker to write a clean, efficient, and standards-conformant libc implementation.
RE/flex is a free and open source computer program written in C++ that generates fast lexical analyzers in C++. RE/flex offers full Unicode support, indentation anchors, word boundaries, lazy quantifiers, and performance tuning options. RE/flex accepts Flex lexer specifications and offers options to generate scanners for Bison parsers. RE/flex includes a fast C++ regular expression library.