Choose a version:
11% The original file has 120826 bytes (118.0k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 12703 bytes (12.4k, 11%).

After GZIP compression these minified files vary in size:
gzip -6 (default)
  5018 bytes (4.9k)
local copy
gzip -9
  5018 bytes (4.9k)
local copy
Boot
  5002 bytes (4.9k)
CDN
cdnjs
  5002 bytes (4.9k)
CDN
jsdelivr
  4997 bytes (4.9k)
CDN
libdeflate -12
  4919 bytes (4.8k)
local copy
kzip -s0 -rn -b0
  4917 bytes (4.8k)
local copy
pigz -11 -n
  4917 bytes (4.8k)
local copy
7zip -mx=9 -tgzip
  4915 bytes (4.8k)
local copy
Zopfli
  4907 bytes (4.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-16.10.1.min.js (or via HTTPS)

You will automatically get the smallest React 16.10.1 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 16.10.1 Zopfli version instead of the best available CDN (1.83% smaller than jsdelivr, 4907 vs. 4997 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 --mls32768 --bsr2 --lazy --ohh

(found October 4, 2019)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 32768  --mls32768
block splitting recursion 2  --bsr2
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-16.10.1.min.js --location | md5sum
868c805083f69ecc8fc3185b2c63cefa  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.10.1.min.zopfli.js.gz | md5sum
868c805083f69ecc8fc3185b2c63cefa  -

SHA1:
curl --silent --compressed https://fb.me/react-16.10.1.min.js --location | sha1sum
fc55edb4a2d1f54b77e7c805ea2d19e09627a66b  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.10.1.min.zopfli.js.gz | sha1sum
fc55edb4a2d1f54b77e7c805ea2d19e09627a66b  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 5002 bytes 868c805083f69ecc8fc3185b2c63cefa September 28, 2019 @ 21:16
cdnjs 5002 bytes 868c805083f69ecc8fc3185b2c63cefa September 28, 2019 @ 21:16
jsdelivr 4997 bytes 868c805083f69ecc8fc3185b2c63cefa October 4, 2019 @ 13:00

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

Other Versions

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

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
4907 bytes -2 bytes zopfli --i1000000 --mls32768 --bsr2 --lazy --ohh October 4, 2019 @ 18:46
4909 bytes -1 byte zopfli --i100000 --mls32768 --bsr2 --lazy --ohh October 4, 2019 @ 17:07
4910 bytes -2 bytes zopfli --i10000 --mls16384 --bsr2 --lazy --ohh October 4, 2019 @ 13:58
4912 bytes -1 byte zopfli --i1000 --mls8 --bsr17 --lazy --ohh October 4, 2019 @ 13:43
4913 bytes zopfli --i100 --mls256 --bsr10 --lazy --ohh October 4, 2019 @ 13:05

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

Most recent activity on October 4, 2019 @ 20:49.

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 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
4915 4915 4913 4915 4915 4915 4914 4913 4913 4913 4913 4913 4908 4907 4907
4912 4912 4916 4915 4913 4913 4913 4913 4913 4913 4913 4912 4913 4914 4914
4914 4914 4913 4915 4913 4914 4912 4914 4913 4913 4913 4916 4914 4913 4913
4914 4914 4914 4915 4913 4912 4912 4912 4913 4913 4913 4913 4913 4913 4913
4914 4914 4911 4915 4913 4915 4912 4913 4913 4913 4913 4916 4914 4913 4913
4915 4915 4914 4913 4914 4912 4912 4913 4913 4913 4913 4912 4914 4914 4914
4915 4915 4914 4914 4913 4911 4912 4912 4913 4913 4913 4916 4915 4914 4914
4917 4917 4915 4913 4914 4912 4912 4912 4913 4913 4913 4916 4914 4913 4913
4914 4914 4914 4914 4914 4911 4912 4914 4913 4913 4913 4913 4915 4914 4914
4912 4912 4912 4914 4914 4911 4913 4914 4913 4913 4913 4916 4914 4915 4915
4915 4915 4913 4914 4914 4912 4913 4912 4913 4913 4913 4914 4913 4913 4913
4914 4914 4914 4915 4913 4912 4912 4913 4913 4913 4913 4916 4914 4911 4911
4915 4915 4912 4914 4912 4913 4913 4914 4913 4913 4913 4916 4913 4913 4913
4913 4913 4912 4914 4913 4911 4912 4914 4913 4913 4913 4916 4914 4914 4914
4914 4914 4913 4914 4913 4912 4912 4913 4913 4913 4913 4916 4914 4914 4914
4913 4913 4913 4915 4913 4911 4912 4914 4913 4913 4913 4913 4914 4914 4914
4912 4912 4913 4914 4913 4911 4912 4914 4913 4913 4913 4916 4915 4913 4913
4915 4915 4914 4914 4914 4912 4912 4913 4913 4913 4913 4914 4914 4914 4914
4912 4912 4915 4913 4913 4912 4912 4912 4913 4913 4913 4913 4914 4913 4913
4914 4914 4914 4913 4914 4913 4912 4914 4913 4913 4913 4916 4914 4914 4914
4915 4915 4914 4913 4913 4911 4912 4914 4913 4913 4913 4916 4915 4913 4913
4913 4913 4912 4915 4914 4911 4912 4914 4913 4913 4913 4915 4914 4914 4914
4912 4912 4911 4913 4913 4912 4912 4912 4913 4913 4913 4914 4914 4914 4914

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 4913 bytes 100%
1,000 4912 bytes -1 byte 100%
10,000 4910 bytes -2 bytes 100%
100,000 4909 bytes -1 byte 0.87%
1,000,000 4907 bytes -2 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
4917 bytes +10 bytes (+0.20%)
4918 bytes +11 bytes (+0.22%) +1 byte
4932 bytes +25 bytes (+0.51%) +15 bytes
4954 bytes +47 bytes (+0.96%) +37 bytes
4965 bytes +58 bytes (+1.18%) +48 bytes
4994 bytes +87 bytes (+1.77%) +77 bytes
5027 bytes +120 bytes (+2.45%) +110 bytes
5057 bytes +150 bytes (+3.06%) +140 bytes
5099 bytes +192 bytes (+3.91%) +182 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 - but your browser doesn't support it.
Algorithm Program Parameters Size Compared To Best Zopfli
Brotli (Wikipedia) brotli brotli -q 11 4419 bytes -488 bytes (-9.94%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 4501 bytes -406 bytes (-8.27%)
Zstandard (Wikipedia) zstd zstd -19 4909 bytes +2 bytes (+0.04%)
LZMA2 (Wikipedia) xz xz -9 4940 bytes +33 bytes (+0.67%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 5005 bytes +98 bytes (+2.00%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 5034 bytes +127 bytes (+2.59%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 5257 bytes +350 bytes (+7.13%)

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 2019.
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