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         <span class="eyebrow">C++11 · header-only · triple-licensed</span>
         <h1>Parse floating-point numbers <span class="grad">at a gigabyte per second</span>.</h1>
         <p class="lede">
           <strong>fast_float</strong> is a header-only C++ implementation of
           <code>std::from_chars</code> for <code>float</code>, <code>double</code>, and integer types.
           Exact IEEE rounding, no allocations, no exceptions — often <strong>many times faster</strong>
           than your standard library.
         </p>
         <div class="cta-row">
           <a class="btn primary" href="#quickstart">Get started</a>
           <a class="btn" href="https://github.com/fastfloat/fast_float">View on GitHub</a>
           <a class="btn ghost" href="https://github.com/fastfloat/fast_float/releases/latest" id="download-latest">
             Download <code class="version-tag" data-version>v{{VERSION}}</code>
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         <div class="hero-meta">
           <span class="badge" id="release-badge">
             <span class="dot"></span> Latest release: <code data-version>v{{VERSION}}</code>
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           <a class="meta-link" href="https://github.com/fastfloat/fast_float/blob/main/LICENSE-APACHE">Apache 2.0</a>
           <a class="meta-link" href="https://github.com/fastfloat/fast_float/blob/main/LICENSE-MIT">MIT</a>
           <a class="meta-link" href="https://github.com/fastfloat/fast_float/blob/main/LICENSE-BOOST">Boost</a>
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     <section id="features" class="section">
       <div class="container">
         <h2>Why fast_float?</h2>
         <p class="section-lede">A drop-in <code>from_chars</code> built for performance-critical code paths.</p>
         <div class="grid features">
           <article class="card">
             <h3>Blazing fast</h3>
             <p>Often <strong>4× faster</strong> than the best competitor and many times faster than typical standard-library implementations. Sustains <strong>1 GB/s</strong> on commodity hardware.</p>
           </article>
           <article class="card">
             <h3>Exact rounding</h3>
             <p>Returns the closest IEEE 754 <code>float</code> or <code>double</code> with round-to-nearest, ties-to-even — bit-for-bit correct.</p>
           </article>
           <article class="card">
             <h3>Header-only</h3>
             <p>Just drop in <code>fast_float.h</code> or use it via CMake, Conan, vcpkg, xmake, or Homebrew. Requires only C++11.</p>
           </article>
           <article class="card">
             <h3>No surprises</h3>
             <p>Does not allocate, does not throw, locale-independent. The interface mirrors C++17 <code>std::from_chars</code>.</p>
           </article>
           <article class="card">
             <h3>Integers too</h3>
             <p>Parses every standard integer type in bases 2–36, plus <code>bool</code>. The same fast, allocation-free interface.</p>
           </article>
           <article class="card">
             <h3>Unicode &amp; formats</h3>
             <p>UTF-8, UTF-16, and UTF-32 inputs. JSON, Fortran, and custom decimal separators via <code>from_chars_advanced</code>.</p>
           </article>
           <article class="card">
             <h3>constexpr-ready</h3>
             <p>In C++20, parse strings at compile time with <code>consteval</code> — zero runtime cost.</p>
           </article>
           <article class="card">
             <h3>Portable</h3>
             <p>Visual Studio, GCC, Clang, MSYS2. Linux, macOS, FreeBSD, Windows. x86-64, ARM, RISC-V, s390x. 32-bit and 64-bit.</p>
           </article>
         </div>
       </div>
     </section>

     <section id="performance" class="section alt">
       <div class="container">
         <h2>Performance</h2>
         <p class="section-lede">
           Parsing random floating-point numbers, measured in megabytes per second
           (higher is better). Source: project benchmark suite on a typical x86-64 box.
         </p>

         <div class="bench">
           <div class="bench-row">
             <span class="bench-label">fast_float</span>
             <div class="bench-bar"><span class="bench-fill primary" style="--w: 100%">1042 MB/s</span></div>
           </div>
           <div class="bench-row">
             <span class="bench-label">abseil</span>
             <div class="bench-bar"><span class="bench-fill" style="--w: 41%">430 MB/s</span></div>
           </div>
           <div class="bench-row">
             <span class="bench-label">netlib</span>
             <div class="bench-bar"><span class="bench-fill" style="--w: 26%">271 MB/s</span></div>
           </div>
           <div class="bench-row">
             <span class="bench-label">double-conversion</span>
             <div class="bench-bar"><span class="bench-fill" style="--w: 22%">225 MB/s</span></div>
           </div>
           <div class="bench-row">
             <span class="bench-label">strtod</span>
             <div class="bench-bar"><span class="bench-fill" style="--w: 18%">191 MB/s</span></div>
           </div>
         </div>

         <details class="repro">
           <summary>Reproduce these numbers</summary>
 <pre data-lang="bash"><code>cmake -B build -D FASTFLOAT_BENCHMARKS=ON
 cmake --build build
 ./build/benchmarks/benchmark</code></pre>
         </details>
       </div>
     </section>

     <section id="quickstart" class="section">
       <div class="container">
         <h2>Quick start</h2>
         <p class="section-lede">Parse a <code>double</code> from a string in three lines.</p>

 <pre data-lang="cpp"><code>#include "fast_float/fast_float.h"
 #include &lt;iostream&gt;
 #include &lt;string&gt;

 int main() {
   std::string input = "3.1416 xyz ";
   double result;
   auto answer = fast_float::from_chars(input.data(),
                                        input.data() + input.size(),
                                        result);
   if (answer.ec != std::errc()) {
     std::cerr &lt;&lt; "parsing failure\n";
     return EXIT_FAILURE;
   }
   std::cout &lt;&lt; "parsed the number " &lt;&lt; result &lt;&lt; '\n';
 }</code></pre>

         <h3>Integers in any base (2–36)</h3>
 <pre data-lang="cpp"><code>uint64_t value;
 std::string hex = "4f0cedc95a718c";
 auto r = fast_float::from_chars(hex.data(), hex.data() + hex.size(), value, 16);
 // value == 22250738585072012</code></pre>

         <h3>UTF-16 input</h3>
 <pre data-lang="cpp"><code>std::u16string input = u"3.1416 xyz ";
 double result;
 auto r = fast_float::from_chars(input.data(), input.data() + input.size(), result);</code></pre>

         <h3>Comma as decimal separator, Fortran, or JSON</h3>
 <pre data-lang="cpp"><code>// "3,1416" — French-style
 fast_float::parse_options opts{fast_float::chars_format::general, ','};
 fast_float::from_chars_advanced(s.data(), s.data() + s.size(), result, opts);

 // "1d+4" — Fortran exponent
 opts = {fast_float::chars_format::fortran};

 // strict JSON per RFC 8259
 opts = {fast_float::chars_format::json};</code></pre>

         <h3>C++20: parse at compile time</h3>
 <pre data-lang="cpp"><code>consteval double parse(std::string_view s) {
   double v;
   auto r = fast_float::from_chars(s.data(), s.data() + s.size(), v);
   return r.ec == std::errc() ? v : -1.0;
 }
 constexpr double pi = parse("3.1415");  // computed at compile time</code></pre>
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     </section>

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       <div class="container">
         <h2>Install</h2>
         <p class="section-lede">Pick the workflow that matches your project.</p>

         <div class="grid install">
           <article class="card">
             <h3>CMake <code>FetchContent</code></h3>
 <pre data-lang="cmake"><code>FetchContent_Declare(
   fast_float
   GIT_REPOSITORY https://github.com/fastfloat/fast_float.git
   GIT_TAG tags/v{{VERSION}}
   GIT_SHALLOW TRUE)
 FetchContent_MakeAvailable(fast_float)
 target_link_libraries(myprogram PUBLIC fast_float)</code></pre>
           </article>

           <article class="card">
             <h3>CPM</h3>
 <pre data-lang="cmake"><code>CPMAddPackage(
   NAME fast_float
   GITHUB_REPOSITORY "fastfloat/fast_float"
   GIT_TAG v{{VERSION}})</code></pre>
           </article>

           <article class="card">
             <h3>Single header</h3>
             <p>Download a pre-amalgamated header — no build system required.</p>
 <pre data-lang="bash"><code>curl -LO https://github.com/fastfloat/fast_float/releases/download/v{{VERSION}}/fast_float.h</code></pre>
           </article>

           <article class="card">
             <h3>Package managers</h3>
             <ul class="bullets">
               <li><a href="https://conan.io/center/recipes/fast_float">Conan</a></li>
               <li><a href="https://formulae.brew.sh/formula/fast_float">Homebrew</a> — <code>brew install fast_float</code></li>
               <li><a href="https://xmake.io">xmake</a></li>
               <li>Fedora — <code>dnf install fast_float-devel</code></li>
               <li><a href="https://repology.org/project/fast-float/versions">More distributions</a></li>
             </ul>
           </article>
         </div>
       </div>
     </section>

     <section id="users" class="section">
       <div class="container">
         <h2>Trusted by</h2>
         <p class="section-lede">fast_float ships inside compilers, browsers, databases, and more.</p>
         <ul class="users">
           <li><strong>GCC</strong> — backs <code>std::from_chars</code> since version 12</li>
           <li><strong>Chromium</strong> — Chrome, Edge, and Opera</li>
           <li><strong>WebKit</strong> — Safari</li>
           <li><strong>Ladybird</strong> — independent browser engine</li>
           <li><strong>DuckDB</strong> — in-process analytical database</li>
           <li><strong>Apache Arrow</strong> — 2–3× faster number parsing</li>
           <li><strong>ClickHouse</strong> — OLAP database</li>
           <li><strong>MySQL</strong></li>
           <li><strong>Boost.JSON</strong></li>
           <li><strong>Blender</strong></li>
           <li><strong>Google Jsonnet</strong></li>
         </ul>
         <p class="aside">
           Ports and bindings exist for
           <a href="https://github.com/aldanor/fast-float-rust/">Rust</a>,
           <a href="https://github.com/wrandelshofer/FastDoubleParser">Java</a>,
           <a href="https://github.com/CarlVerret/csFastFloat">C#</a>,
           <a href="https://github.com/kolemannix/ffc.h">C</a>, and
           <a href="https://github.com/eddelbuettel/rcppfastfloat">R</a>.
         </p>
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     </section>

     <section id="papers" class="section alt">
       <div class="container">
         <h2>The research behind it</h2>
         <ul class="papers">
           <li>
             Daniel Lemire,
             <a href="https://arxiv.org/abs/2101.11408"><strong>Number Parsing at a Gigabyte per Second</strong></a>.
             <em>Software: Practice and Experience</em> 51(8), 2021.
           </li>
           <li>
             Noble Mushtak, Daniel Lemire,
             <a href="https://arxiv.org/abs/2212.06644"><strong>Fast Number Parsing Without Fallback</strong></a>.
             <em>Software: Practice and Experience</em> 53(7), 2023.
           </li>
         </ul>
       </div>
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	<span class="eyebrow">C++11 · header-only · triple-licensed</span>
	<h1>Parse floating-point numbers <span class="grad">at a gigabyte per second</span>.</h1>
	<p class="lede">
	<strong>fast_float</strong> is a header-only C++ implementation of
	<code>std::from_chars</code> for <code>float</code>, <code>double</code>, and integer types.
	Exact IEEE rounding, no allocations, no exceptions — often <strong>many times faster</strong>
	than your standard library.
	</p>
	<div class="cta-row">
	<a class="btn primary" href="#quickstart">Get started</a>
	<a class="btn" href="https://github.com/fastfloat/fast_float">View on GitHub</a>
	<a class="btn ghost" href="https://github.com/fastfloat/fast_float/releases/latest" id="download-latest">
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	<section id="features" class="section">
	<div class="container">
	<h2>Why fast_float?</h2>
	<p class="section-lede">A drop-in <code>from_chars</code> built for performance-critical code paths.</p>
	<div class="grid features">
	<article class="card">
	<h3>Blazing fast</h3>
	<p>Often <strong>4× faster</strong> than the best competitor and many times faster than typical standard-library implementations. Sustains <strong>1 GB/s</strong> on commodity hardware.</p>
	</article>
	<article class="card">
	<h3>Exact rounding</h3>
	<p>Returns the closest IEEE 754 <code>float</code> or <code>double</code> with round-to-nearest, ties-to-even — bit-for-bit correct.</p>
	</article>
	<article class="card">
	<h3>Header-only</h3>
	<p>Just drop in <code>fast_float.h</code> or use it via CMake, Conan, vcpkg, xmake, or Homebrew. Requires only C++11.</p>
	</article>
	<article class="card">
	<h3>No surprises</h3>
	<p>Does not allocate, does not throw, locale-independent. The interface mirrors C++17 <code>std::from_chars</code>.</p>
	</article>
	<article class="card">
	<h3>Integers too</h3>
	<p>Parses every standard integer type in bases 2–36, plus <code>bool</code>. The same fast, allocation-free interface.</p>
	</article>
	<article class="card">
	<h3>Unicode & formats</h3>
	<p>UTF-8, UTF-16, and UTF-32 inputs. JSON, Fortran, and custom decimal separators via <code>from_chars_advanced</code>.</p>
	</article>
	<article class="card">
	<h3>constexpr-ready</h3>
	<p>In C++20, parse strings at compile time with <code>consteval</code> — zero runtime cost.</p>
	</article>
	<article class="card">
	<h3>Portable</h3>
	<p>Visual Studio, GCC, Clang, MSYS2. Linux, macOS, FreeBSD, Windows. x86-64, ARM, RISC-V, s390x. 32-bit and 64-bit.</p>
	</article>
	</div>
	</div>
	</section>

	<section id="performance" class="section alt">
	<div class="container">
	<h2>Performance</h2>
	<p class="section-lede">
	Parsing random floating-point numbers, measured in megabytes per second
	(higher is better). Source: project benchmark suite on a typical x86-64 box.
	</p>

	<div class="bench">
	<div class="bench-row">
	<span class="bench-label">fast_float</span>
	<div class="bench-bar"><span class="bench-fill primary" style="--w: 100%">1042 MB/s</span></div>
	</div>
	<div class="bench-row">
	<span class="bench-label">abseil</span>
	<div class="bench-bar"><span class="bench-fill" style="--w: 41%">430 MB/s</span></div>
	</div>
	<div class="bench-row">
	<span class="bench-label">netlib</span>
	<div class="bench-bar"><span class="bench-fill" style="--w: 26%">271 MB/s</span></div>
	</div>
	<div class="bench-row">
	<span class="bench-label">double-conversion</span>
	<div class="bench-bar"><span class="bench-fill" style="--w: 22%">225 MB/s</span></div>
	</div>
	<div class="bench-row">
	<span class="bench-label">strtod</span>
	<div class="bench-bar"><span class="bench-fill" style="--w: 18%">191 MB/s</span></div>
	</div>
	</div>

	<details class="repro">
	<summary>Reproduce these numbers</summary>
	<pre data-lang="bash"><code>cmake -B build -D FASTFLOAT_BENCHMARKS=ON
	cmake --build build
	./build/benchmarks/benchmark</code></pre>
	</details>
	</div>
	</section>

	<section id="quickstart" class="section">
	<div class="container">
	<h2>Quick start</h2>
	<p class="section-lede">Parse a <code>double</code> from a string in three lines.</p>

	<pre data-lang="cpp"><code>#include "fast_float/fast_float.h"
	#include <iostream>
	#include <string>

	int main() {
	std::string input = "3.1416 xyz ";
	double result;
	auto answer = fast_float::from_chars(input.data(),
	input.data() + input.size(),
	result);
	if (answer.ec != std::errc()) {
	std::cerr << "parsing failure\n";
	return EXIT_FAILURE;
	}
	std::cout << "parsed the number " << result << '\n';
	}</code></pre>

	<h3>Integers in any base (2–36)</h3>
	<pre data-lang="cpp"><code>uint64_t value;
	std::string hex = "4f0cedc95a718c";
	auto r = fast_float::from_chars(hex.data(), hex.data() + hex.size(), value, 16);
	// value == 22250738585072012</code></pre>

	<h3>UTF-16 input</h3>
	<pre data-lang="cpp"><code>std::u16string input = u"3.1416 xyz ";
	double result;
	auto r = fast_float::from_chars(input.data(), input.data() + input.size(), result);</code></pre>

	<h3>Comma as decimal separator, Fortran, or JSON</h3>
	<pre data-lang="cpp"><code>// "3,1416" — French-style
	fast_float::parse_options opts{fast_float::chars_format::general, ','};
	fast_float::from_chars_advanced(s.data(), s.data() + s.size(), result, opts);

	// "1d+4" — Fortran exponent
	opts = {fast_float::chars_format::fortran};

	// strict JSON per RFC 8259
	opts = {fast_float::chars_format::json};</code></pre>

	<h3>C++20: parse at compile time</h3>
	<pre data-lang="cpp"><code>consteval double parse(std::string_view s) {
	double v;
	auto r = fast_float::from_chars(s.data(), s.data() + s.size(), v);
	return r.ec == std::errc() ? v : -1.0;
	}
	constexpr double pi = parse("3.1415"); // computed at compile time</code></pre>
	</div>
	</section>

	<section id="install" class="section alt">
	<div class="container">
	<h2>Install</h2>
	<p class="section-lede">Pick the workflow that matches your project.</p>

	<div class="grid install">
	<article class="card">
	<h3>CMake <code>FetchContent</code></h3>
	<pre data-lang="cmake"><code>FetchContent_Declare(
	fast_float
	GIT_REPOSITORY https://github.com/fastfloat/fast_float.git
	GIT_TAG tags/v{{VERSION}}
	GIT_SHALLOW TRUE)
	FetchContent_MakeAvailable(fast_float)
	target_link_libraries(myprogram PUBLIC fast_float)</code></pre>
	</article>

	<article class="card">
	<h3>CPM</h3>
	<pre data-lang="cmake"><code>CPMAddPackage(
	NAME fast_float
	GITHUB_REPOSITORY "fastfloat/fast_float"
	GIT_TAG v{{VERSION}})</code></pre>
	</article>

	<article class="card">
	<h3>Single header</h3>
	<p>Download a pre-amalgamated header — no build system required.</p>
	<pre data-lang="bash"><code>curl -LO https://github.com/fastfloat/fast_float/releases/download/v{{VERSION}}/fast_float.h</code></pre>
	</article>

	<article class="card">
	<h3>Package managers</h3>
	<ul class="bullets">
	<li><a href="https://conan.io/center/recipes/fast_float">Conan</a></li>
	<li><a href="https://formulae.brew.sh/formula/fast_float">Homebrew</a> — <code>brew install fast_float</code></li>
	<li><a href="https://xmake.io">xmake</a></li>
	<li>Fedora — <code>dnf install fast_float-devel</code></li>
	<li><a href="https://repology.org/project/fast-float/versions">More distributions</a></li>
	</ul>
	</article>
	</div>
	</div>
	</section>

	<section id="users" class="section">
	<div class="container">
	<h2>Trusted by</h2>
	<p class="section-lede">fast_float ships inside compilers, browsers, databases, and more.</p>
	<ul class="users">
	<li><strong>GCC</strong> — backs <code>std::from_chars</code> since version 12</li>
	<li><strong>Chromium</strong> — Chrome, Edge, and Opera</li>
	<li><strong>WebKit</strong> — Safari</li>
	<li><strong>Ladybird</strong> — independent browser engine</li>
	<li><strong>DuckDB</strong> — in-process analytical database</li>
	<li><strong>Apache Arrow</strong> — 2–3× faster number parsing</li>
	<li><strong>ClickHouse</strong> — OLAP database</li>
	<li><strong>MySQL</strong></li>
	<li><strong>Boost.JSON</strong></li>
	<li><strong>Blender</strong></li>
	<li><strong>Google Jsonnet</strong></li>
	</ul>
	<p class="aside">
	Ports and bindings exist for
	<a href="https://github.com/aldanor/fast-float-rust/">Rust</a>,
	<a href="https://github.com/wrandelshofer/FastDoubleParser">Java</a>,
	<a href="https://github.com/CarlVerret/csFastFloat">C#</a>,
	<a href="https://github.com/kolemannix/ffc.h">C</a>, and
	<a href="https://github.com/eddelbuettel/rcppfastfloat">R</a>.
	</p>
	</div>
	</section>

	<section id="papers" class="section alt">
	<div class="container">
	<h2>The research behind it</h2>
	<ul class="papers">
	<li>
	Daniel Lemire,
	<a href="https://arxiv.org/abs/2101.11408"><strong>Number Parsing at a Gigabyte per Second</strong></a>.
	<em>Software: Practice and Experience</em> 51(8), 2021.
	</li>
	<li>
	Noble Mushtak, Daniel Lemire,
	<a href="https://arxiv.org/abs/2212.06644"><strong>Fast Number Parsing Without Fallback</strong></a>.
	<em>Software: Practice and Experience</em> 53(7), 2023.
	</li>
	</ul>
	</div>
	</section>
	</main>

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	<div class="container footer-grid">
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	<strong>fast_float</strong>
	<p>Triple-licensed under Apache 2.0, MIT, and Boost. Use it however you like.</p>
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	<h4>Project</h4>
	<ul>
	<li><a href="https://github.com/fastfloat/fast_float">GitHub repository</a></li>
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	<h4>Learn more</h4>
	<ul>
	<li><a href="https://arxiv.org/abs/2101.11408">Number Parsing at a Gigabyte per Second</a></li>
	<li><a href="https://www.youtube.com/watch?v=AVXgvlMeIm4">Go Systems 2020 talk</a></li>
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