google/re2

Health v2 · maintenance only

Adoption not part of the score

9785 stars · 1241 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

RE2 is a C++ regular expression library that guarantees linear-time matching, making it safe for handling regexes from untrusted users. It uses automata-based engines instead of backtracking, avoiding exponential runtime and stack overflow, at the cost of not supporting backreferences or look-around.

Use cases

• match user-supplied regex patterns safely without denial-of-service risk
• run regex matching in multithreaded C++ services
• replace PCRE where exponential backtracking is a security concern
• parse and extract substrings from large text volumes with predictable performance
• limit memory usage when compiling untrusted regular expressions

When to choose

• you need guaranteed linear match time on untrusted input
• you want thread-friendly regex matching without locks
• you need bounded memory usage and no stack overflow risk
• you don't need backreferences or look-around assertions

When to avoid

• you rely on backreferences or look-around constructs
• you need full Perl/PCRE feature compatibility
• your patterns are simple and a backtracking engine is fast enough

Facets

library · maturity stable

parser search-engine parsers developer-tools cpp cross-platform regex regular-expressions linear-time-matching text-processing dfa algorithms

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