Choose a version:
12% The original file has 105138 bytes (102.7k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 12463 bytes (12.2k, 12%).

After GZIP compression these minified files vary in size:
Boot
  4919 bytes (4.8k)
CDN
cdnjs
  4919 bytes (4.8k)
CDN
gzip -6 (default)
  4919 bytes (4.8k)
local copy
gzip -9
  4917 bytes (4.8k)
local copy
zultra
  4819 bytes (4.7k)
local copy
kzip -s0 -rn -b0
  4818 bytes (4.7k)
local copy
libdeflate -12
  4817 bytes (4.7k)
local copy
pigz -11 -n
  4817 bytes (4.7k)
local copy
7zip -mx=9 -tgzip
  4816 bytes (4.7k)
local copy
Zopfli
  4810 bytes (4.7k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-16.14.0.min.js (or via HTTPS)

You will automatically get the smallest React 16.14.0 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 109 bytes by using my React 16.14.0 Zopfli version instead of the best available CDN (2.27% smaller than cdnjs, 4810 vs. 4919 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 --mls2 --bsr20 --lazy --ohh

(found October 17, 2020)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 2  --mls2
block splitting recursion 20  --bsr20
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-16.14.0.min.js --location | md5sum
63d498e143f421cc44dfb64f22fef270  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.14.0.min.zopfli.js.gz | md5sum
63d498e143f421cc44dfb64f22fef270  -

SHA1:
curl --silent --compressed https://fb.me/react-16.14.0.min.js --location | sha1sum
1b4c8b769c3094cf499b3e7072c3776ef39ed02d  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.14.0.min.zopfli.js.gz | sha1sum
1b4c8b769c3094cf499b3e7072c3776ef39ed02d  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4919 bytes 63d498e143f421cc44dfb64f22fef270 October 15, 2020 @ 00:12
cdnjs 4919 bytes 63d498e143f421cc44dfb64f22fef270 October 15, 2020 @ 00:12

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

Other Versions

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

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
4810 bytes -1 byte zopfli --i100000 --mls2 --bsr20 --lazy --ohh October 17, 2020 @ 09:25
4811 bytes -1 byte zopfli --i10000 --mls2 --bsr23 --lazy --ohh October 16, 2020 @ 14:05
4812 bytes -1 byte zopfli --i1000 --mls32 --bsr19 --lazy --ohh October 16, 2020 @ 13:57
4813 bytes zopfli --i100 --mls64 --bsr19 --lazy --ohh October 16, 2020 @ 13:51

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

Most recent activity on October 19, 2020 @ 21:38.

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
4814 4814 4814 4814 4813 4813 4814 4814 4814 4814 4814 4814 4812 4814 4814
4813 4813 4813 4813 4812 4813 4812 4812 4813 4814 4814 4814 4814 4816 4816
4810 4810 4812 4813 4812 4813 4812 4812 4814 4811 4814 4814 4811 4814 4814
4810 4810 4813 4813 4811 4814 4814 4813 4812 4814 4814 4814 4813 4812 4812
4810 4810 4812 4813 4814 4813 4814 4813 4812 4814 4814 4814 4813 4814 4814
4810 4810 4814 4813 4814 4811 4814 4813 4811 4814 4814 4814 4813 4814 4814
4813 4813 4812 4812 4814 4813 4814 4814 4812 4814 4814 4814 4811 4814 4814
4813 4813 4810 4812 4812 4810 4814 4814 4811 4811 4814 4814 4813 4814 4814
4813 4813 4813 4813 4814 4812 4814 4813 4814 4814 4814 4814 4813 4812 4812
4812 4812 4812 4812 4813 4812 4814 4815 4811 4814 4814 4814 4813 4814 4814
4813 4813 4812 4812 4812 4811 4814 4813 4815 4814 4814 4814 4814 4814 4814
4810 4810 4813 4811 4812 4813 4814 4814 4812 4813 4814 4814 4811 4813 4813
4810 4810 4813 4812 4814 4811 4814 4813 4814 4814 4814 4814 4811 4812 4812
4813 4813 4813 4812 4812 4812 4814 4814 4812 4814 4814 4814 4813 4812 4812
4813 4813 4813 4813 4811 4810 4812 4814 4814 4814 4814 4814 4811 4814 4814
4810 4810 4812 4811 4811 4811 4812 4814 4812 4814 4814 4814 4812 4814 4814
4810 4810 4814 4813 4812 4811 4814 4813 4811 4813 4814 4814 4812 4814 4814
4810 4810 4814 4813 4812 4811 4814 4814 4812 4814 4814 4814 4811 4812 4812
4813 4813 4813 4812 4812 4811 4814 4813 4812 4813 4814 4814 4813 4812 4812
4810 4810 4810 4812 4812 4813 4814 4813 4812 4814 4814 4814 4811 4813 4813
4813 4813 4813 4812 4814 4813 4814 4814 4812 4814 4814 4814 4812 4812 4812
4811 4811 4811 4812 4812 4810 4814 4814 4812 4814 4814 4814 4814 4814 4814
4812 4812 4812 4813 4813 4814 4814 4814 4812 4811 4814 4814 4812 4814 4814

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 4813 bytes 100%
1,000 4812 bytes -1 byte 100%
10,000 4811 bytes -1 byte 100%
100,000 4810 bytes -1 byte 15.65%
1,000,000 4810 bytes 7.25%
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
4818 bytes +8 bytes (+0.17%)
4818 bytes +8 bytes (+0.17%)
4824 bytes +14 bytes (+0.29%) +6 bytes
4862 bytes +52 bytes (+1.08%) +44 bytes
4885 bytes +75 bytes (+1.56%) +67 bytes
4902 bytes +92 bytes (+1.91%) +84 bytes
4929 bytes +119 bytes (+2.47%) +111 bytes
4962 bytes +152 bytes (+3.16%) +144 bytes
4999 bytes +189 bytes (+3.93%) +181 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 4336 bytes -474 bytes (-9.85%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 4415 bytes -395 bytes (-8.21%)
Zstandard (Wikipedia) zstd zstd -19 4813 bytes +3 bytes (+0.06%)
LZMA2 (Wikipedia) xz xz -9 4840 bytes +30 bytes (+0.62%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 4912 bytes +102 bytes (+2.12%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 4937 bytes +127 bytes (+2.64%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 5175 bytes +365 bytes (+7.59%)

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 2020.
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.