Choose a version:
10% The original file has 109740 bytes (107.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 10737 bytes (10.5k, 10%).

After GZIP compression these minified files vary in size:
gzip -6 (default)
  4275 bytes (4.2k)
local copy
gzip -9
  4275 bytes (4.2k)
local copy
Boot
  4269 bytes (4.2k)
CDN
cdnjs
  4269 bytes (4.2k)
CDN
libdeflate -12
  4190 bytes (4.1k)
local copy
7zip -mx=9 -tgzip
  4189 bytes (4.1k)
local copy
pigz -11 -n
  4189 bytes (4.1k)
local copy
zultra
  4189 bytes (4.1k)
local copy
kzip -s0 -rn -b1
  4187 bytes (4.1k)
local copy
Zopfli
  4179 bytes (4.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-18.1.0.min.js (or via HTTPS)

You will automatically get the smallest React 18.1.0 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 90 bytes by using my React 18.1.0 Zopfli version instead of the best available CDN (2.15% smaller than cdnjs, 4179 vs. 4269 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 --bsr16 --lazy --ohh

(found May 3, 2022)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 4096  --mls4096
block splitting recursion 16  --bsr16
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-18.1.0.min.js --location | md5sum
7e1d5d0fc28b4a063e2fe2028bfe917c  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-18.1.0.min.zopfli.js.gz | md5sum
7e1d5d0fc28b4a063e2fe2028bfe917c  -

SHA1:
curl --silent --compressed https://fb.me/react-18.1.0.min.js --location | sha1sum
346d6dd0b4e6403f8c437b1fa8bb521f980857ee  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-18.1.0.min.zopfli.js.gz | sha1sum
346d6dd0b4e6403f8c437b1fa8bb521f980857ee  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4269 bytes 7e1d5d0fc28b4a063e2fe2028bfe917c April 27, 2022 @ 07:05
cdnjs 4269 bytes 7e1d5d0fc28b4a063e2fe2028bfe917c April 27, 2022 @ 00:39

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
4179 bytes -1 byte zopfli --i1000000 --mls4096 --bsr16 --lazy --ohh May 3, 2022 @ 10:55
4180 bytes -1 byte zopfli --i100000 --mls4096 --bsr22 --lazy --ohh May 2, 2022 @ 18:47
4181 bytes -1 byte zopfli --i100000 --mls32768 --bsr14 --lazy --ohh May 2, 2022 @ 18:32
4182 bytes -1 byte zopfli --i10000 --mls4096 --bsr20 --lazy --ohh May 2, 2022 @ 16:36
4183 bytes -1 byte zopfli --i1000 --mls4096 --bsr21 --lazy --ohh May 2, 2022 @ 16:21
4184 bytes -2 bytes zopfli --i1000 --mls4096 --bsr10 --lazy --ohh May 2, 2022 @ 16:21
4186 bytes zopfli --i100 --mls8192 --bsr4 --lazy --ohh May 2, 2022 @ 15:54

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

Most recent activity on May 3, 2022 @ 17:49.

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, 100,000 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
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4187 4186 4188 4188
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4181 4181 4181
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4185 4183 4183
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4186 4186 4186
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4181 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4186 4186 4186
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4185 4183 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4185 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4186 4181 4181
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4185 4186 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4183 4181 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4185 4186 4186
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4179 4181 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4186 4186 4186
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4185 4185 4185

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 4186 bytes 100%
1,000 4183 bytes -3 bytes 100%
10,000 4182 bytes -1 byte 100%
100,000 4180 bytes -2 bytes 7.54%
1,000,000 4179 bytes -1 byte 2.90%
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
4187 bytes +8 bytes (+0.19%)
4187 bytes +8 bytes (+0.19%)
4221 bytes +42 bytes (+1.01%) +34 bytes
4236 bytes +57 bytes (+1.36%) +49 bytes
4260 bytes +81 bytes (+1.94%) +73 bytes
4294 bytes +115 bytes (+2.75%) +107 bytes
4322 bytes +143 bytes (+3.42%) +135 bytes
4352 bytes +173 bytes (+4.14%) +165 bytes
4385 bytes +206 bytes (+4.93%) +198 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 3747 bytes -432 bytes (-10.34%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 3866 bytes -313 bytes (-7.49%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 4187 bytes +8 bytes (+0.19%)
Zstandard (Wikipedia) zstd zstd -19 4189 bytes +10 bytes (+0.24%)
LZMA2 (Wikipedia) xz xz -9 4240 bytes +61 bytes (+1.46%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 4301 bytes +122 bytes (+2.92%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 4644 bytes +465 bytes (+11.13%)

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.