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{fmt}

C++ library for type-safe, fast text formatting and printing

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What it is

{fmt} is a C++ library for formatting strings and printing output, using a Python-like brace syntax as a replacement for printf and iostreams. It provides implementations of the C++20 std::format facility and the std::print function added in C++23, validates format strings during compilation, and supports dates, containers, colors, Unicode, and user-defined types. C++ developers adopt it to get correct, round-trip floating-point output and quick number conversion without pulling in external dependencies, and it can be used header-only.

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Facts

Stars
25,884 GitHub stars.
25,884

Forks
3,087
Commits
8,044
Contributors
500+
Language
C++
License
MIT
Last commit
Oct 18, 2026
On GitHub since
December 2012
First release
February 2015
Platforms
library
Self-hostable
No
Tags
  • utility-library

Last synced from GitHub on Oct 20, 2026

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What people are saying

Updated Oct 21, 2026
  • Hacker NewsFmt – A Modern Formatting LibraryMay 24, 2020 · 44 points · 12 comments (opens Hacker News in a new tab)
  • Hacker NewsFmtlib / fmt A modern formatting libraryJul 20, 2025 · 7 points · 0 comments (opens Hacker News in a new tab)
  • Hacker NewsFmt: A Modern and Lightweight C++ Formatting LibraryAug 14, 2024 · 3 points · 0 comments (opens Hacker News in a new tab)
  • Hacker NewsA Modern Formatting LibraryJul 5, 2024 · 3 points · 0 comments (opens Hacker News in a new tab)
  • Hacker NewsDragonbox: A New Floating-Point Binary-to-Decimal Conversion Algorithm [pdf]Aug 27, 2026 · 2 points · 0 comments (opens Hacker News in a new tab)
  • Bluesky“fmt: an open-source Formatting Library providing a fast and safe Alternative to C stdio and C++ iostreams #Programming #C++”Nov 24, 2025 · 2 likes · 0 replies (opens Bluesky in a new tab)
  • Hacker News{fmt} v12: 60% faster double formatting, full constexpr, and C++ 20 modulesSep 17, 2025 · 2 points · 0 comments (opens Hacker News in a new tab)
  • Hacker News{fmt}: a modern C++ string formatting libraryJun 3, 2024 · 2 points · 0 comments (opens Hacker News in a new tab)
  • Hacker NewsA modern formatting libraryJun 14, 2019 · 2 points · 0 comments (opens Hacker News in a new tab)
  • Bluesky“The API is really intuitive: all the power of the printf syntax with nearly everything checked at compile time. You can even add formatters for your own…”Mar 4, 2025 · 1 like · 0 replies (opens Bluesky in a new tab)