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{fmt}

A C++ library for fast, type-safe text formatting, as a safer alternative to printf and iostreams.

GitHub Download 12.2.0
Stars
25.9k
Forks
3.1k
Licence
MIT
Language
C++
Last update
4 days ago
Type
Library

What it is

{fmt} is an open-source C++ library for turning values into formatted text, such as printing to the screen, writing files, or building strings. The README describes it as a fast and safe alternative to C stdio and C++ iostreams. It uses a Python-like format string syntax and is an implementation of C++20 std::format and C++23 std::print.

  • Print formatted messages with fmt::print, for example fmt::print("The answer is {}.", 42)
  • Format dates and times using the fmt/chrono.h header
  • Print containers such as std::vector using the fmt/ranges.h header
  • Write formatted output to a file with fmt::output_file
  • Print colored and styled text to a terminal using fmt/color.h

Great for

  • C++ developers who want a printing or string formatting API that is safer than printf
  • Projects that need fast numeric output, such as converting many numbers to text
  • Teams that need consistent output across Linux, macOS, and Windows
  • Developers who want to format user-defined types with a custom formatter

Not ideal for

  • People who do not write C++, since this is a C++ library
  • Projects that already use C++20 std::format or C++23 std::print and need nothing extra, since the standard library may cover their needs (the README says {fmt} implements these standards, but does not discuss migration)
  • Non-programmers looking for an end-user application
Step-by-step guide: how to use {fmt}Install, first run, examples, tips and FAQs

How to get it

  1. 1

    Clone and build from source

    You'll need: A C++ compiler with C++11 or later support (exact minimum not confirmed in the truncated README) · CMake (the README does not specify this in the visible portion)

    Clone the repository

    git clone https://github.com/fmtlib/fmt.git
  2. 2

    Run it

    • Clone the repository or download the release zip (fmt-12.2.0.zip)
    • Add the include directory to your project, or build the library with CMake as described in the full README
    • Include <fmt/core.h> in your source file
    • Call fmt::print("Hello, world!\n"); and compile
  3. 3

    Get the most out of it

    • Use FMT_HEADER_ONLY to avoid building a separate library, as mentioned in the README
    • Use the compile API to precompile format strings for faster runtime, as the README notes
    • Use fmt/chrono.h and fmt/ranges.h when you need date, time, or container formatting
    • Use the printf-compatible API if you are migrating from printf

Downloads

Source code (.zip)main branch · straight from GitHubRelease 12.2.02 files incl. fmt-12.2.0.zipOfficial website & docsfmt.dev

Strengths

  • The README reports a broad test suite, continuous fuzzing via OSS-Fuzz, and a compile-time check of format strings
  • Has no external dependencies and is available under the permissive MIT license
  • The README reports performance advantages over common standard library formatting methods, with benchmarks linked

Trade-offs

  • Benchmark results in the README come from the maintainers and specific hardware and compilers; your results may differ
  • Adds a library to your build, and the README's compile-time tables show the header-based build is slower to compile than the module build
  • The README's pages are truncated here, so details of build options and configuration are not fully visible

How it compares

ProjectStarsTypeLevelUpdatedBest for
fmt (this)25.9kLibraryintermediate4 days agoC++ developers who want a printing or string formatting API that is safer than printf
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JoltPhysics12.1kLibraryadvanced4 days agoC++ game developers who need a physics engine for rigid bodies and collisions
awesome-cpp74.2kCurated listbeginner6 days agoC++ developers looking for a library for a specific task
gin89.5kLibraryintermediate27 days agoGo developers building REST APIs
cpp-httplib17kLibrarybeginner6 days agoC++ developers who need a simple embedded HTTP server or client without a large framework

Stats synced from GitHub. The assessment above was drafted with AI from the project's README on 2026-10-29 and may miss recent changes — check the README before relying on a command. MIT licence: free to use, modify and distribute, including commercially, as long as you keep the copyright notice.