fastfloat/fast_float

Health v2 · maintenance only

Adoption not part of the score

2088 stars · 192 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

fast_float is a header-only C++11 library providing fast, exact implementations of std::from_chars for float, double, and integer types, parsing ASCII decimal strings with correct IEEE 754 round-to-even rounding. It sustains roughly a gigabyte per second on commodity hardware, does not allocate or throw, and is used in GCC 12, MySQL, DuckDB, Chromium, Redis, and WebKit.

Use cases

• parse floating-point numbers from strings faster than strtod
• replace std::from_chars on compilers lacking full C++17 support
• parse numeric CSV or JSON fields at high throughput
• convert ASCII integers in bases 2-36 without allocations
• get exact IEEE 754 rounding when parsing decimals
• parse numbers in a C++11 codebase with C++17-style API

When to choose

• you need bit-exact, locale-independent number parsing with round-to-even
• number parsing is a performance bottleneck in your C++ code
• you want a header-only, dependency-free, allocation-free parser
• you need portability across GCC, Clang, MSVC, and ARM/x86/RISC-V

When to avoid

• you need locale-aware parsing with custom thousands separators or locale decimal points
• your standard library's from_chars or strtod performance is already sufficient
• you are writing C rather than C++ (consider a C port instead)
• you need to parse exotic number formats beyond decimal, hex, infinity, and nan

Facets

library · maturity stable

parser serialization developer-tools developer-tools performance cpp cross-platform windows bsd header-only number-parsing from-chars floating-point simd high-performance cpp11 cpp17 algorithms data-engineering linux macos

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