Repolode
Submit
fmtlib

fmtlib/fmt

A C++ formatting library offering a fast, type-safe alternative to C stdio and iostreams, implementing C++20 std::format.

View on GitHubWebsite
Stars
25,887
Forks
3,089
Open issues
16
Last commit
3 days ago

What is it?

{fmt} is an open-source C++ library for formatting text, aiming to be a faster and safer alternative to C stdio and C++ iostreams. It uses a Python-like format string syntax and implements the C++20 std::format and C++23 std::print interfaces, so code can be written in a familiar style.

The library checks format strings at compile time, so mistakes such as applying an invalid specifier to a string are reported as compile errors. It also provides a printf-compatible API, formatting for chrono dates and times, containers and ranges, colored terminal output, and a floating-point formatter based on the Dragonbox algorithm. Users can add formatting support for their own types.

{fmt} has no external dependencies and is available as a small set of headers or as a header-only build. It is licensed under MIT and is used by projects such as ClickHouse, MongoDB, PyTorch and spdlog.

Key features

  • 01Python-style format string syntax with positional arguments
  • 02Implements C++20 std::format and C++23 std::print
  • 03Compile-time checking of format strings
  • 04Fast floating-point formatting using the Dragonbox algorithm
  • 05Chrono, range and container formatting support
  • 06Header-only mode with no external dependencies

Use cases

  • Replacing printf or iostreams in performance-sensitive C++ code
  • Building logging messages in libraries such as spdlog
  • Formatting dates, times and containers for console output
  • Writing portable C++ code that targets C++20 or older compilers

Topics

#cpp#formatting#printf#unicode#header-only#performance#c-plus-plus#chrono#cross-platform#floating-point

FAQ

What is fmt?
A C++ formatting library offering a fast, type-safe alternative to C stdio and iostreams, implementing C++20 std::format. {fmt} is an open-source C++ library for formatting text, aiming to be a faster and safer alternative to C stdio and C++ iostreams. It uses a Python-like format string syntax and implements the C++20 std::format and C++23 std::print interfaces, so code can be written in a familiar style.
Is fmt free to use? What license does it have?
fmt is open source under the MIT license. Check the license terms before using it in commercial products.
Is fmt still maintained?
Actively maintained. The last commit to fmt was on Oct 18, 2026.
What can I use fmt for?
Replacing printf or iostreams in performance-sensitive C++ code Building logging messages in libraries such as spdlog Formatting dates, times and containers for console output Writing portable C++ code that targets C++20 or older compilers
Where can I get fmt?
The source code and installation instructions are on GitHub: https://github.com/fmtlib/fmt

Summary generated by AI from the project's README. GitHub stats refresh daily.

Related projects