Choose a version:
12% The original file has 101989 bytes (99.6k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 12548 bytes (12.3k, 12%).

After GZIP compression these minified files vary in size:
gzip -6 (default)
  4848 bytes (4.7k)
local copy
gzip -9
  4843 bytes (4.7k)
local copy
Boot
  4836 bytes (4.7k)
CDN
cdnjs
  4836 bytes (4.7k)
CDN
jsdelivr
  4828 bytes (4.7k)
CDN
libdeflate -12
  4755 bytes (4.6k)
local copy
pigz -11 -n
  4753 bytes (4.6k)
local copy
7zip -mx=9 -tgzip
  4752 bytes (4.6k)
local copy
kzip -s0 -rn -b1
  4750 bytes (4.6k)
local copy
Zopfli
  4745 bytes (4.6k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-16.8.2.min.js (or via HTTPS)

You will automatically get the smallest React 16.8.2 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 83 bytes by using my React 16.8.2 Zopfli version instead of the best available CDN (1.75% smaller than jsdelivr, 4745 vs. 4828 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 --mls2048 --bsr18 --lazy --ohh

(found August 7, 2019)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 2048  --mls2048
block splitting recursion 18  --bsr18
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-16.8.2.min.js --location | md5sum
d89ca949bd7d0511e0450f67ceff9699  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.8.2.min.zopfli.js.gz | md5sum
d89ca949bd7d0511e0450f67ceff9699  -

SHA1:
curl --silent --compressed https://fb.me/react-16.8.2.min.js --location | sha1sum
5fe7b0bf89587a1f01ccf36a552b4187b6a0d5e7  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.8.2.min.zopfli.js.gz | sha1sum
5fe7b0bf89587a1f01ccf36a552b4187b6a0d5e7  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4836 bytes d89ca949bd7d0511e0450f67ceff9699 February 15, 2019 @ 19:45
cdnjs 4836 bytes d89ca949bd7d0511e0450f67ceff9699 February 15, 2019 @ 19:45
jsdelivr 4828 bytes d89ca949bd7d0511e0450f67ceff9699 August 7, 2019 @ 16:21

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

Other Versions

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

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
4745 bytes -1 byte zopfli --i100000 --mls2048 --bsr18 --lazy --ohh August 7, 2019 @ 18:57
4746 bytes -1 byte zopfli --i10000 --mls2048 --bsr18 --lazy --ohh August 7, 2019 @ 17:35
4747 bytes -2 bytes zopfli --i1000 --mls2048 --bsr13 --lazy --ohh August 7, 2019 @ 16:42
4749 bytes zopfli --i100 --mls2048 --bsr14 --lazy --ohh August 7, 2019 @ 16:27

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

Most recent activity on August 8, 2019 @ 16:51.

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
4754 4754 4754 4754 4752 4752 4750 4754 4750 4750 4750 4749 4748 4752 4752
4750 4750 4750 4752 4750 4750 4750 4750 4750 4750 4750 4748 4748 4748 4748
4750 4750 4755 4752 4751 4750 4751 4752 4750 4750 4750 4749 4752 4754 4754
4750 4750 4751 4751 4750 4750 4752 4754 4750 4750 4750 4749 4749 4749 4749
4752 4752 4753 4752 4753 4751 4752 4755 4750 4750 4745 4749 4748 4752 4752
4750 4750 4749 4751 4752 4750 4750 4750 4750 4750 4750 4749 4748 4753 4753
4752 4752 4751 4752 4751 4751 4752 4754 4750 4750 4745 4748 4752 4752 4752
4752 4752 4752 4752 4752 4753 4751 4754 4750 4750 4750 4748 4749 4749 4749
4751 4751 4751 4752 4751 4751 4753 4754 4750 4750 4750 4749 4749 4749 4749
4750 4750 4752 4752 4752 4753 4750 4754 4750 4750 4745 4745 4749 4749 4749
4750 4750 4751 4752 4752 4750 4752 4754 4750 4750 4746 4749 4753 4753 4753
4752 4752 4752 4754 4753 4754 4752 4753 4750 4750 4750 4749 4749 4749 4749
4752 4752 4752 4752 4752 4750 4752 4754 4750 4750 4750 4748 4754 4754 4754
4751 4751 4752 4752 4752 4751 4752 4754 4750 4750 4750 4749 4749 4752 4752
4752 4752 4751 4752 4752 4750 4753 4754 4750 4750 4745 4750 4752 4753 4753
4752 4752 4752 4752 4752 4753 4752 4754 4750 4750 4750 4748 4752 4754 4754
4751 4751 4752 4752 4752 4751 4752 4754 4750 4750 4750 4748 4749 4754 4753
4749 4749 4751 4752 4752 4751 4752 4754 4750 4750 4750 4748 4749 4749 4749
4751 4751 4754 4752 4752 4753 4754 4754 4750 4750 4750 4748 4748 4754 4754
4749 4749 4749 4752 4752 4753 4752 4754 4750 4750 4745 4748 4754 4753 4754
4753 4753 4752 4752 4752 4752 4751 4755 4750 4750 4750 4749 4748 4748 4748
4753 4753 4751 4752 4753 4752 4753 4752 4750 4750 4746 4749 4749 4749 4749
4755 4755 4752 4755 4752 4753 4752 4754 4750 4750 4750 4749 4748 4749 4749

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 4749 bytes 100%
1,000 4747 bytes -2 bytes 100%
10,000 4746 bytes -1 byte 100%
100,000 4745 bytes -1 byte 3.19%
1,000,000 4745 bytes 1.74%
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
4751 bytes +6 bytes (+0.13%) +1 byte
4750 bytes +5 bytes (+0.11%)
4765 bytes +20 bytes (+0.42%) +15 bytes
4794 bytes +49 bytes (+1.03%) +44 bytes
4819 bytes +74 bytes (+1.56%) +69 bytes
4853 bytes +108 bytes (+2.28%) +103 bytes
4882 bytes +137 bytes (+2.89%) +132 bytes
4914 bytes +169 bytes (+3.56%) +164 bytes
4933 bytes +188 bytes (+3.96%) +183 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 4265 bytes -480 bytes (-10.12%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 4352 bytes -393 bytes (-8.28%)
Zstandard (Wikipedia) zstd zstd -19 4738 bytes -7 bytes (-0.15%)
LZMA2 (Wikipedia) xz xz -9 4784 bytes +39 bytes (+0.82%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 4887 bytes +142 bytes (+2.99%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 4899 bytes +154 bytes (+3.25%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 5120 bytes +375 bytes (+7.90%)

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