Cargo Features

regex = { version = "1.10.2", default-features = false, features = ["std", "logging", "use_std", "perf", "perf-dfa", "perf-dfa-full", "perf-onepass", "perf-backtrack", "perf-inline", "perf-literal", "perf-cache", "unicode", "unicode-age", "unicode-bool", "unicode-case", "unicode-gencat", "unicode-perl", "unicode-script", "unicode-segment", "unstable", "pattern"] }

Features are documented in the "Crate features" section of the crate docs:*/#crate-features

default = perf, std, unicode

These default features are set whenever regex is added without default-features = false somewhere in the dependency tree.

Enables default features of regex-syntax

std default use_std?


The 'std' feature permits the regex crate to use the standard library. This is intended to support future use cases where the regex crate may be able to compile without std, and instead just rely on 'core' and 'alloc' (for example). Currently, this isn't supported, and removing the 'std' feature will prevent regex from compiling.

Enables std of optional aho-corasick, optional memchr, regex-automata, and regex-syntax


This feature enables the 'log' crate to emit messages. This is usually only useful for folks working on the regex crate itself, but can be useful if you're trying hard to do some performance hacking on regex patterns themselves. Note that you'll need to pair this with a crate like 'env_logger'
to actually emit the log messages somewhere.

Enables logging of optional aho-corasick, optional memchr, and regex-automata

use_std = std

The 'use_std' feature is DEPRECATED. It will be removed in regex 2. Until then, it is an alias for the 'std' feature.

perf default = perf-backtrack, perf-cache, perf-dfa, perf-inline, perf-literal, perf-onepass


Enables all default performance features. Note that this specifically does not include perf-dfa-full, because it leads to higher compile times and bigger binaries, and the runtime performance improvement is not obviously worth it.

perf-dfa perf

Enables use of a lazy DFA when possible.

Enables hybrid of regex-automata


Enables use of a fully compiled DFA when possible.

Enables dfa-build and dfa-search of regex-automata

perf-onepass perf

Enables use of the one-pass regex matcher, which speeds up capture searches even beyond the backtracker.

Enables dfa-onepass of regex-automata

perf-backtrack perf

Enables use of a bounded backtracker, which speeds up capture searches.

Enables nfa-backtrack of regex-automata

perf-inline perf

Enables aggressive use of inlining.

Enables perf-inline of regex-automata

perf-literal perf

Enables literal optimizations.

Enables perf-literal of regex-automata, aho-corasick and memchr

perf-cache perf

Enables fast caching. (If disabled, caching is still used, but is slower.)
Currently, this feature has no effect. It used to remove the thread_local dependency and use a slower internal cache, but now the default cache has been improved and thread_local is no longer a dependency at all.

unicode default = unicode-age, unicode-bool, unicode-case, unicode-gencat, unicode-perl, unicode-script, unicode-segment


Enables all Unicode features. This expands if new Unicode features are added.

Enables unicode of regex-automata and regex-syntax

unicode-age unicode

Enables use of the Age property, e.g., \p{Age:3.0}.

Enables unicode-age of regex-automata and regex-syntax

unicode-bool unicode

Enables use of a smattering of boolean properties, e.g., \p{Emoji}.

Enables unicode-bool of regex-automata and regex-syntax

unicode-case unicode

Enables Unicode-aware case insensitive matching, e.g., (?i)β.

Enables unicode-case of regex-automata and regex-syntax

unicode-gencat unicode

Enables Unicode general categories, e.g., \p{Letter} or \pL.

Enables unicode-gencat of regex-automata and regex-syntax

unicode-perl unicode

Enables Unicode-aware Perl classes corresponding to \w, \s and \d.

Enables unicode-perl and unicode-word-boundary of regex-automata, unicode-perl of regex-syntax

unicode-script unicode

Enables Unicode scripts and script extensions, e.g., \p{Greek}.

Enables unicode-script of regex-automata and regex-syntax

unicode-segment unicode

Enables Unicode segmentation properties, e.g., \p{gcb=Extend}.

Enables unicode-segment of regex-automata and regex-syntax

unstable = pattern

UNSTABLE FEATURES (requires Rust nightly)

A blanket feature that governs whether unstable features are enabled or not.
Unstable features are disabled by default, and typically rely on unstable features in rustc itself.

pattern unstable?

Enable to use the unstable pattern traits defined in std. This is enabled by default if the unstable feature is enabled.