JulienFourel/fastminify-minification-benchmark

FastMinify minification benchmark, edition 2026-10

Measurements of 27 minifier settings on 2,669 public files under permissive licenses: 10 JavaScript, 6 CSS, 4 HTML, 6 JSON, 2,636 SVG and 7 XML files, taken from npm packages, from GitHub repositories at a fixed commit and from the WHATWG HTML review draft of July 2026. One row per file and setting (10,705 rows): the size before and after minification, raw, gzip (level 9) and brotli (quality 11), whether the output parses again, and the median time over repeated runs. One row records a tool error instead of a size.

Tools: Terser, esbuild, SWC, oxc-minify and uglify-js for JavaScript; CSSO, Lightning CSS, esbuild, cssnano and clean-css for CSS; html-minifier-terser, minify-html and htmlnano for HTML; jq for JSON; SVGO for SVG; minify-xml and xmllint for XML. The minifiers of FastMinify, the code that runs on fastminify.com, are measured by the same script, one row per preset. Every setting is written out in the tools file.

Measured on 2026-10-17 on one machine (Apple M4 Max, 64 GB, macOS 26.6.2, Node v26.4.0). Times depend on the machine and compare tools within this edition only. Sizes can be reproduced: the scripts, the pinned package versions and the input files are in the deposit, with the SHA-256 of every input and output.

Built by FastMinify, free online minifiers for JavaScript, CSS, HTML, JSON, XML and SVG that run in the browser.

Citable record: https://doi.org/10.5281/zenodo.23433365 (Zenodo).

Files

File	What it holds	Rows
results.csv	One row per input file and tool setting	10,705
tools.csv	One row per tool setting, with the exact options passed to the tool	27
corpus.csv	One row per input file: source, version or commit, address, SHA-256, size, license	2,669
run-2026-10.json	Machine, Node version, start and end time, timing rules
bench-2026-10.tar.gz	The scripts and pinned dependencies that produced the files
corpus-2026-10.tar.gz	The 2,669 input files, with the license and notice files of each source

Totals on this corpus

Sums over the files of each language where every setting produced an output, so that each row covers the same files. A total says what happened on these files and nothing more: one large file can weigh more than all the others.

JavaScript (10 files)

Files where every setting succeeded: 10 of 10. Before minification: 5,637,983 bytes, 1,142,675 with gzip, 899,755 with brotli.

Tool	Settings	Minified bytes	Gzip bytes	Brotli bytes	Outputs that do not parse	Sum of median times (ms)
fastminify	normal	1,791,240	553,972	473,648	0	4,332
fastminify	aggressive	1,745,960	548,544	470,392	0	6,998
terser	default	1,809,323	566,618	484,012	0	2,996
esbuild	minify	1,821,841	581,392	499,257	0	202
@swc/core	minify	1,788,075	562,698	481,088	0	424
oxc-minify	default	1,794,251	565,060	484,670	0	106
uglify-js	default	1,774,871	563,481	482,140	0	5,605

CSS (6 files)

Files where every setting succeeded: 6 of 6. Before minification: 1,593,647 bytes, 161,522 with gzip, 106,426 with brotli.

Tool	Settings	Minified bytes	Gzip bytes	Brotli bytes	Outputs that do not parse	Sum of median times (ms)
fastminify	normal	1,356,056	149,919	97,886	0	127
fastminify	aggressive	1,331,964	150,043	99,195	0	237
csso	default	1,338,588	151,049	99,630	0	187
lightningcss	minify	1,334,411	148,388	96,795	0	23
esbuild	minify	1,361,244	150,829	98,545	0	39
cssnano	default	1,312,942	150,567	99,293	0	424
clean-css	level1	1,357,854	150,573	98,533	0	96

HTML (4 files)

Files where every setting succeeded: 3 of 4. Before minification: 95,009 bytes, 12,414 with gzip, 9,904 with brotli.

Tool	Settings	Minified bytes	Gzip bytes	Brotli bytes	Outputs that do not parse	Sum of median times (ms)
fastminify	default	40,419	10,022	7,976	not checked	0.19
html-minifier-terser	collapse	40,397	10,017	7,996	not checked	8.58
@minify-html/node	default	36,990	9,882	8,078	not checked	0.76
htmlnano	safe	40,560	10,152	8,310	not checked	6.87

Files left out of the totals because one setting failed on them:

File	Tool	Settings	Raw bytes	Minified bytes	Gzip bytes	Brotli bytes	Median time (ms) or error
whatwg-html-review-draft html-review-draft-2026-07.html	fastminify	default	12,879,245	12,515,346	1,848,495	1,240,067	148
whatwg-html-review-draft html-review-draft-2026-07.html	html-minifier-terser	collapse	12,879,245	13,107,063	1,876,414	1,249,525	1,367
whatwg-html-review-draft html-review-draft-2026-07.html	@minify-html/node	default	12,879,245				the tool crashed the Node process (SIGSEGV) on this file
whatwg-html-review-draft html-review-draft-2026-07.html	htmlnano	safe	12,879,245	12,545,492	1,858,579	1,245,913	823

JSON (6 files)

Files where every setting succeeded: 6 of 6. Before minification: 14,199,411 bytes, 1,063,455 with gzip, 502,848 with brotli.

Tool	Settings	Minified bytes	Gzip bytes	Brotli bytes	Outputs that do not parse	Sum of median times (ms)
fastminify	default	7,747,070	756,768	423,574	0	116
jq	compact	7,747,134	757,136	423,751	0	334

SVG (2,636 files)

Files where every setting succeeded: 2,636 of 2,636. Before minification: 3,287,826 bytes, 1,426,008 with gzip, 1,245,324 with brotli.

Tool	Settings	Minified bytes	Gzip bytes	Brotli bytes	Outputs that do not parse	Sum of median times (ms)
fastminify	safe	3,223,186	1,409,873	1,231,373	0	170
fastminify	default	3,203,404	1,402,303	1,225,083	0	1,179
fastminify	aggressive	2,794,642	1,264,085	1,094,873	0	1,839
svgo	preset-default	3,203,599	1,402,383	1,225,174	0	624

XML (7 files)

Files where every setting succeeded: 7 of 7. Before minification: 796,582 bytes, 145,600 with gzip, 119,606 with brotli.

Tool	Settings	Minified bytes	Gzip bytes	Brotli bytes	Outputs that do not parse	Sum of median times (ms)
fastminify	default	615,165	117,143	97,256	0	3.79
minify-xml	default	632,025	122,198	101,806	0	39
xmllint	noblanks	703,848	141,684	116,890	0	24

Columns of results.csv

• edition: 2026-10.
• language: js, css, html, json, svg or xml.
• source, source_version, file: the npm package and version, the GitHub repository and commit, or the web page and its version, and the path of the file in it.
• file_sha256: SHA-256 of the input file.
• tool, tool_version, settings_id: the tool setting, described in the tools file. FastMinify rows give the commit of the FastMinify source they were built from.
• bytes_raw, bytes_raw_gzip, bytes_raw_brotli: size of the input file, alone and compressed (gzip level 9, brotli quality 11, Node zlib).
• bytes_min, bytes_min_gzip, bytes_min_brotli: size of the output, alone and compressed with the same settings.
• output_sha256: SHA-256 of the output, to check a reproduction.
• output_valid: yes when the output parses again (acorn for JavaScript, css-tree for CSS, JSON.parse for JSON, xmllint for SVG and XML), no when it does not, empty for HTML (no strict parser used).
• runs, duration_ms_median, duration_ms_min: number of timed runs, then the median and the minimum time of one run in milliseconds. In-process tools are timed as a function call; jq and xmllint are timed as a new process, start included.
• error: the tool's message when it refused the file; the size columns are then empty.

Method

• Input files come from npm tarballs (integrity checked against the registry), from GitHub at a fixed commit and from a dated WHATWG review draft. Only files that are not already minified were chosen.
• Each tool runs with the options written in the tools file, nothing else. A default means the tool's own default for this version.
• Timing: 2 warm-up runs then 10 timed runs per file and tool; 1 warm-up and 3 timed runs when one run takes over 5 s; 1 and 1 over 30 s. Median and minimum in milliseconds, process.hrtime.bigint().
• FastMinify rows run the FastMinify source code at commit e3e3ed8c3a85, built into one file with esbuild (bench/engines/fastminify-engines.mjs). FastMinify times cover the whole site function, including the checks it runs before minifying (a CSS syntax check, a JSON parse).
• One machine, one run of the whole benchmark, from 2026-10-17T07:51:00.005Z to 2026-10-17T07:59:49.344Z.

What the data supports and what it does not

• It gives, for each file and setting, the bytes removed before and after gzip or brotli, and the time on this machine on 2026-10-17.
• It does not say which tool is better in general: results depend on the files, the versions and the settings. Totals above cover these files only.
• It does not check that the output behaves like the input. Some settings change behavior on purpose: the FastMinify JavaScript presets drop console calls and debugger statements, and the FastMinify JSON preset rewrites numbers.
• The FastMinify HTML and XML minifiers use regular expressions. They remove spaces around every = sign, including in text, <pre> blocks and inline scripts, which can change content.
• SVGO 4 reports that the FastMinify SVG presets configure removeViewBox and removeTitle, which are no longer part of its preset-default; those two options have no effect.

Reproduce

tar -xzf bench-2026-10.tar.gz && cd bench
npm ci
node corpus.ts fetch
node run.ts 2026-10

Node 24 or later. jq and xmllint must be installed for their rows. engines/build.ts rebuilds the FastMinify file from the FastMinify source, which is not public; the built file is included.

Related work

• privatenumber/minification-benchmarks: JavaScript minifiers on popular libraries, updated on every pull request.
• GoalSmashers/css-minification-benchmark: CSS minifiers.

License and credit

The measurements, tables and scripts are licensed under CC BY 4.0: free to copy, chart and republish, including commercially. Please credit "FastMinify" with a link to https://fastminify.com/. The input files in the corpus archive keep their own licenses and copyright notices (MIT, ISC, Apache-2.0, CC BY 4.0), listed in the corpus file. Tool and library names belong to their authors and are used only to identify them. FastMinify is one of the tools measured, by the same script as the others.

Also published at

• Zenodo (citable, DOI 10.5281/zenodo.23433365): https://doi.org/10.5281/zenodo.23433365, with the scripts and the input files
• FastMinify: https://fastminify.com/