Choose a version:
10% The original file has 109891 bytes (107.3k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 10756 bytes (10.5k, 10%).

After GZIP compression these minified files vary in size:
gzip -6 (default)
  4292 bytes (4.2k)
local copy
gzip -9
  4292 bytes (4.2k)
local copy
Boot
  4289 bytes (4.2k)
CDN
cdnjs
  4289 bytes (4.2k)
CDN
libdeflate -12
  4209 bytes (4.1k)
local copy
7zip -mx=9 -tgzip
  4208 bytes (4.1k)
local copy
zultra
  4208 bytes (4.1k)
local copy
pigz -11 -n
  4207 bytes (4.1k)
local copy
kzip -s0 -rn -b0
  4206 bytes (4.1k)
local copy
Zopfli
  4198 bytes (4.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-18.0.0.min.js (or via HTTPS)

You will automatically get the smallest React 18.0.0 file, ETag caching is available and
if your browser doesn't support GZIP decompression then the uncompressed version will be sent.

Currently best Zopfli settings

Save 91 bytes by using my React 18.0.0 Zopfli version instead of the best available CDN (2.17% smaller than cdnjs, 4198 vs. 4289 bytes):
You can use my super-compressed files for whatever purpose you like as long as you respect the library's original license agreement.
There are no restrictions from my side - but please avoid hot-linking if you run a high-traffic website.

These command-line settings yielded the best compression ratio so far (Linux version of zopfli-krzymod):
zopfli --i1000000 --mb8 --mls4096 --bsr8 --lazy --ohh

(found April 4, 2022)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 4096  --mls4096
block splitting recursion 8  --bsr8
lazy matching in LZ77 yes  --lazy
optimized Huffman headers yes  --ohh
initial random W for iterations 1  --rw1
initial random Z for iterations 2  --rz2

Verify file integrity

After decompression, my uncompressed files are identical to the original ones:

MD5:
curl --silent --compressed https://fb.me/react-18.0.0.min.js --location | md5sum
7a8cb96f4add9f833fc95944c8e202d7  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-18.0.0.min.zopfli.js.gz | md5sum
7a8cb96f4add9f833fc95944c8e202d7  -

SHA1:
curl --silent --compressed https://fb.me/react-18.0.0.min.js --location | sha1sum
c6cb33b876f44d8be8f07e281c578b9055510489  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-18.0.0.min.zopfli.js.gz | sha1sum
c6cb33b876f44d8be8f07e281c578b9055510489  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4289 bytes 7a8cb96f4add9f833fc95944c8e202d7 April 4, 2022 @ 10:59
cdnjs 4289 bytes 7a8cb96f4add9f833fc95944c8e202d7 March 29, 2022 @ 22:35

Note: only the MD5 hashes are shown to keep things simple.

Other Versions

Available React versions at minime.stephan-brumme.com:

18.1.0, 18.0.0,
17.0.2, 17.0.1, 17.0.0,
16.14.0,
16.13.1, 16.13.0,
16.12.0,
16.11.0,
16.10.2, 16.10.1, 16.10.0,
16.9.0,
16.8.6, 16.8.5, 16.8.4, 16.8.3, 16.8.2, 16.8.1, 16.8.0,
16.7.0,
16.6.3, 16.6.1, 16.6.0,
16.5.2, 16.5.1, 16.5.0,
16.4.2, 16.4.1, 16.4.0,
16.3.2, 16.3.1, 16.3.0,
16.2.0,
16.1.1, 16.1.0, 16.0.0,
15.6.2, 15.6.1, 15.6.0,
15.5.2, 15.5.1, 15.5.0,
15.4.2, 15.4.1, 15.4.0,
15.3.2, 15.3.1, 15.3.0,
15.2.1, 15.2.0,
15.1.0,
15.0.2, 15.0.1, 15.0.0,
0.14.8, 0.14.7, 0.14.6, 0.14.5, 0.14.4, 0.14.3, 0.14.2, 0.14.1, 0.14.0,
0.13.3, 0.13.2, 0.13.1, 0.13.0,
0.12.2, 0.12.1, 0.12.0,
0.11.2, 0.11.1, 0.11.0,
0.10.0

The project site contains an overview how well these versions were compressed.
Other interesting projects are AngularJS, BackboneJS, Bootstrap, D3, Dojo, Ember, jQuery, Knockout, lodash, Socket.IO, ThreeJS, UnderscoreJS and Vue.

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
4198 bytes -1 byte zopfli --i1000000 --mls4096 --bsr8 --lazy --ohh April 4, 2022 @ 12:44
4199 bytes -1 byte zopfli --i1000000 --mls8192 --bsr25 --lazy --ohh April 4, 2022 @ 12:36
4200 bytes -1 byte zopfli --i100000 --mls4096 --bsr15 --lazy --ohh April 4, 2022 @ 11:19
4201 bytes -1 byte zopfli --i10000 --mls4096 --bsr15 --lazy --ohh April 4, 2022 @ 11:10
4202 bytes -3 bytes zopfli --i1000 --mls4096 --bsr8 --lazy --ohh April 4, 2022 @ 11:06
4205 bytes zopfli --i100 --mls4096 --bsr21 --lazy --ohh April 4, 2022 @ 11:01

If there are multiple parameter sets yielding the same compressed size, only the first one found is shown.

Most recent activity on April 4, 2022 @ 16:10.

Heatmaps

This Zopfli heatmap visualizes how compression changes when modifying the --bsr and --mls parameter.
Cell's contents is the best filesize achieved (in bytes, hover with mouse over cells to see number of iterations).

Good parameters are green, bad are red. The best and worst are bold as well.
The brightness of the blue background color indicates how many iterations were processed:
10,000 or 1,000,000.
bsr \ mls
2 4 8 16 32 64 128 256 512 1024 2048 4096 8192 16384 32768
bsr \ mls
2 4 8 16 32 64 128 256 512 1024 2048 4096 8192 16384 32768
4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4204 4204 4204
4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4203 4202 4204 4204
4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4202 4204 4204 4204
4210 4210 4205 4205 4205 4205 4205 4205 4205 4205 4205 4199 4199 4203 4203
4210 4210 4205 4205 4205 4205 4205 4205 4205 4205 4205 4198 4204 4204 4204
4209 4209 4205 4205 4205 4205 4205 4205 4205 4205 4205 4199 4200 4202 4202
4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4199 4203 4203 4203
4210 4210 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4204 4204 4204
4209 4209 4205 4205 4205 4205 4205 4205 4205 4205 4205 4202 4204 4204 4204
4209 4209 4205 4205 4205 4205 4205 4205 4205 4205 4205 4204 4202 4202 4202
4205 4205 4205 4205 4205 4204 4205 4205 4205 4205 4205 4203 4204 4204 4204
4209 4209 4205 4205 4205 4205 4205 4205 4205 4205 4205 4199 4204 4204 4204
4205 4205 4205 4205 4205 4204 4205 4205 4205 4205 4205 4202 4202 4203 4203
4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4202 4202 4203 4203
4205 4205 4205 4205 4205 4204 4205 4205 4205 4205 4205 4204 4199 4204 4204
4210 4210 4205 4205 4205 4205 4205 4205 4205 4205 4205 4202 4203 4203 4203
4210 4210 4205 4205 4205 4204 4205 4205 4205 4205 4205 4204 4204 4203 4203
4210 4210 4205 4205 4205 4205 4205 4205 4205 4205 4205 4199 4203 4203 4203
4210 4210 4205 4205 4205 4204 4205 4205 4205 4205 4205 4204 4203 4203 4203
4210 4210 4205 4205 4205 4205 4205 4205 4205 4205 4205 4205 4202 4204 4204
4209 4209 4205 4205 4205 4205 4205 4205 4205 4205 4205 4200 4199 4204 4204
4210 4210 4205 4205 4205 4205 4205 4205 4205 4205 4205 4199 4204 4204 4204
4209 4209 4205 4205 4205 4204 4205 4205 4205 4205 4205 4202 4204 4203 4203

Due to the Monte Carlo design of my search algorithm, not all parameters have reached the same number of iterations yet:
Iterations Min. Bytes Reduction Coverage
100 4205 bytes 100%
1,000 4202 bytes -3 bytes 100%
10,000 4201 bytes -1 byte 100%
100,000 4200 bytes -1 byte 3.48%
1,000,000 4198 bytes -2 bytes 3.48%
10,000,000

KZIP has far less options available for tuning/optimization. I only played around with the number of blocks (parameter -n):
Blocks Min. Bytes Compared To Best Zopfli Compared To Best KZIP
4206 bytes +8 bytes (+0.19%)
4206 bytes +8 bytes (+0.19%)
4214 bytes +16 bytes (+0.38%) +8 bytes
4246 bytes +48 bytes (+1.14%) +40 bytes
4280 bytes +82 bytes (+1.95%) +74 bytes
4305 bytes +107 bytes (+2.55%) +99 bytes
4333 bytes +135 bytes (+3.22%) +127 bytes
4364 bytes +166 bytes (+3.95%) +158 bytes
4399 bytes +201 bytes (+4.79%) +193 bytes

Non-DEFLATE Algorithms

Archivers based on completely different compression algorithms often produce superior results.
Unfortunately, browsers only support gzip compression at the moment.
However, support for Brotli is constantly growing - for example, your browser actually supports it !
Algorithm Program Parameters Size Compared To Best Zopfli
Brotli (Wikipedia) brotli brotli -q 11 3764 bytes -434 bytes (-10.34%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 3886 bytes -312 bytes (-7.43%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 4205 bytes +7 bytes (+0.17%)
Zstandard (Wikipedia) zstd zstd -19 4207 bytes +9 bytes (+0.21%)
LZMA2 (Wikipedia) xz xz -9 4256 bytes +58 bytes (+1.38%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 4322 bytes +124 bytes (+2.95%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 4659 bytes +461 bytes (+10.98%)

Detailled Analysis

I wrote a DEFLATE decoder in Javascript. Click the button below to start a client-side analysis of the smallest gzipped files (may take a second):


Notes: pigz is a fast open source multi-threaded implementation of gzip written by one of the original authors of gzip.
However, when using compression level 11, pigz actually switches to the slower Zopfli algorithm and isn't multi-threaded anymore.
KrzyMOD's extensions to Zopfli offer the highest level of configuration and is therefore used for my brute-force search.
Ken Silverman wrote the closed-source KZIP compression program and Jonathon Fowler ported it to Linux.
Defluff was created by Joachim Henke; DeflOpt is a tool by Ben Jos Walbeehm.

website made by Stephan Brumme in 2015 and still improving in 2022.
all timestamps are displayed in central european time. see my changelog.
no flash, not even images or external css files - and everything squeezed into a single html file.
which was handsomely compressed before releasing it into the wild internet - obviously.

please visit my homepage and my blog, too.
email: minime (at) stephan-brumme.com

All trademarks are property of their respective owners. You know, the boring legal stuff.