Choose a version:
10% The original file has 109910 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 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 -b0
  4187 bytes (4.1k)
local copy
Zopfli
  4180 bytes (4.1k)
local copy
Zopfli (defluff)
  4179 bytes (4.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-18.2.0.min.js (or via HTTPS)

You will automatically get the smallest React 18.2.0 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 89 bytes by using my React 18.2.0 Zopfli version instead of the best available CDN (2.13% smaller than cdnjs, 4180 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 --i100000 --mb8 --mls4096 --bsr6 --lazy --ohh

(found July 4, 2022)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 4096  --mls4096
block splitting recursion 6  --bsr6
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

Even Smaller Files Thanks To Defluff

Zopfli's output can be further optimized by the defluff tool.
In this particular case, defluff saves 1 more byte (4179 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed https://fb.me/react-18.2.0.min.js --location | md5sum
d86dcdbfed4c273c4742744941259902  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-18.2.0.min.zopfli.js.gz | md5sum
d86dcdbfed4c273c4742744941259902  -

SHA1:
curl --silent --compressed https://fb.me/react-18.2.0.min.js --location | sha1sum
98089a33d0cf2fa4b3e1ba9b7eeb9b8ba0ac82a7  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-18.2.0.min.zopfli.js.gz | sha1sum
98089a33d0cf2fa4b3e1ba9b7eeb9b8ba0ac82a7  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4269 bytes d86dcdbfed4c273c4742744941259902 June 15, 2022 @ 05:20
cdnjs 4269 bytes d86dcdbfed4c273c4742744941259902 June 14, 2022 @ 22:06

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

Other Versions

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

18.2.0,
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
4180 bytes -1 byte zopfli --i100000 --mls4096 --bsr6 --lazy --ohh July 4, 2022 @ 12:02
4181 bytes -1 byte zopfli --i10000 --mls4096 --bsr6 --lazy --ohh June 30, 2022 @ 12:27
4182 bytes -1 byte zopfli --i10000 --mls4096 --bsr8 --lazy --ohh June 30, 2022 @ 12:15
4183 bytes -2 bytes zopfli --i1000 --mls4096 --bsr16 --lazy --ohh June 30, 2022 @ 11:57
4185 bytes zopfli --i100 --mls4096 --bsr11 --lazy --ohh June 30, 2022 @ 11:18

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

Most recent activity on July 4, 2022 @ 15:58.

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 4187 4188 4188
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4181 4186 4186
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4180 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4183 4185 4183 4183
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4180 4187 4187 4187
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4183 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4184 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4183 4187 4187 4187
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 4185 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4186 4185 4185
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 4183 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 4183 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4183 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4183 4185 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4183 4185 4187 4187
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4183 4183 4185 4185
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4181 4187 4187 4187
4187 4187 4187 4187 4187 4187 4187 4187 4187 4187 4188 4180 4185 4184 4184
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 4185 bytes 100%
1,000 4183 bytes -2 bytes 100%
10,000 4181 bytes -2 bytes 100%
100,000 4180 bytes -1 byte 3.48%
1,000,000 4180 bytes 0.87%
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 +7 bytes (+0.17%)
4187 bytes +7 bytes (+0.17%)
4220 bytes +40 bytes (+0.96%) +33 bytes
4234 bytes +54 bytes (+1.29%) +47 bytes
4259 bytes +79 bytes (+1.89%) +72 bytes
4294 bytes +114 bytes (+2.73%) +107 bytes
4320 bytes +140 bytes (+3.35%) +133 bytes
4352 bytes +172 bytes (+4.11%) +165 bytes
4385 bytes +205 bytes (+4.90%) +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 -433 bytes (-10.36%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 3867 bytes -313 bytes (-7.49%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 4187 bytes +7 bytes (+0.17%)
Zstandard (Wikipedia) zstd zstd -19 4189 bytes +9 bytes (+0.22%)
LZMA2 (Wikipedia) xz xz -9 4240 bytes +60 bytes (+1.44%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 4309 bytes +129 bytes (+3.09%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 4644 bytes +464 bytes (+11.10%)

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.