Choose a version:
12% The original file has 100355 bytes (98.0k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 11800 bytes (11.5k, 12%).

After GZIP compression these minified files vary in size:
gzip -6 (default)
  4690 bytes (4.6k)
local copy
gzip -9
  4686 bytes (4.6k)
local copy
Boot
  4677 bytes (4.6k)
CDN
cdnjs
  4677 bytes (4.6k)
CDN
jsdelivr
  4670 bytes (4.6k)
CDN
libdeflate -12
  4597 bytes (4.5k)
local copy
7zip -mx=9 -tgzip
  4595 bytes (4.5k)
local copy
kzip -s0 -rn -b0
  4595 bytes (4.5k)
local copy
pigz -11 -n
  4593 bytes (4.5k)
local copy
Zopfli
  4589 bytes (4.5k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-16.7.0.min.js (or via HTTPS)

You will automatically get the smallest React 16.7.0 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 81 bytes by using my React 16.7.0 Zopfli version instead of the best available CDN (1.77% smaller than jsdelivr, 4589 vs. 4670 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 --i10000 --mb8 --mls32768 --bsr11 --lazy --ohh

(found August 7, 2019)
Description Value Parameter
iterations 10000  --i10000
maximum blocks 8  --mb8
maximum length score 32768  --mls32768
block splitting recursion 11  --bsr11
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-16.7.0.min.js --location | md5sum
6797a59ed573f8a4c1c74db6e354f2eb  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.7.0.min.zopfli.js.gz | md5sum
6797a59ed573f8a4c1c74db6e354f2eb  -

SHA1:
curl --silent --compressed https://fb.me/react-16.7.0.min.js --location | sha1sum
46c8c78a0773d7210f28d97d340c91b3a7a187cb  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-16.7.0.min.zopfli.js.gz | sha1sum
46c8c78a0773d7210f28d97d340c91b3a7a187cb  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4677 bytes 6797a59ed573f8a4c1c74db6e354f2eb December 20, 2018 @ 02:45
cdnjs 4677 bytes 6797a59ed573f8a4c1c74db6e354f2eb December 20, 2018 @ 02:45
jsdelivr 4670 bytes 6797a59ed573f8a4c1c74db6e354f2eb August 7, 2019 @ 19:05

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
4589 bytes -1 byte zopfli --i10000 --mls32768 --bsr11 --lazy --ohh August 7, 2019 @ 17:47
4590 bytes -2 bytes zopfli --i1000 --mls4096 --bsr22 --lazy --ohh August 7, 2019 @ 16:43
4592 bytes -1 byte zopfli --i1000 --mls512 --bsr8 --lazy --ohh August 7, 2019 @ 16:43
4593 bytes zopfli --i100 --mls1024 --bsr20 --lazy --ohh August 7, 2019 @ 16:25

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 @ 14:38.

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
4593 4593 4594 4593 4594 4592 4595 4594 4592 4592 4592 4592 4594 4594 4594
4592 4592 4592 4592 4594 4594 4593 4594 4592 4592 4592 4593 4591 4589 4589
4594 4594 4592 4594 4594 4594 4593 4593 4592 4592 4592 4592 4594 4593 4593
4593 4593 4593 4594 4594 4594 4593 4592 4592 4592 4592 4592 4597 4597 4597
4593 4593 4594 4594 4594 4598 4594 4594 4592 4592 4592 4592 4590 4597 4597
4594 4594 4594 4594 4594 4594 4594 4594 4592 4592 4592 4593 4598 4598 4598
4594 4594 4593 4594 4594 4598 4594 4593 4592 4592 4592 4593 4594 4589 4589
4593 4593 4593 4596 4592 4594 4593 4592 4592 4592 4592 4593 4589 4589 4589
4593 4593 4593 4594 4594 4595 4593 4593 4592 4592 4592 4589 4594 4598 4598
4594 4594 4594 4594 4594 4594 4593 4592 4592 4592 4592 4593 4598 4594 4594
4594 4594 4594 4594 4594 4594 4594 4594 4592 4592 4592 4590 4594 4598 4598
4594 4594 4593 4594 4594 4594 4594 4594 4592 4592 4592 4592 4594 4598 4598
4594 4594 4594 4594 4594 4594 4594 4593 4592 4592 4592 4590 4598 4593 4593
4593 4593 4594 4593 4594 4594 4593 4593 4592 4592 4592 4593 4590 4594 4594
4594 4594 4593 4594 4594 4594 4594 4594 4592 4592 4592 4590 4594 4595 4595
4594 4594 4593 4594 4594 4594 4594 4593 4592 4592 4592 4593 4593 4593 4593
4594 4594 4593 4593 4594 4594 4593 4594 4592 4592 4592 4593 4598 4598 4598
4593 4593 4593 4594 4594 4594 4593 4593 4592 4592 4592 4593 4589 4589 4589
4593 4593 4593 4594 4594 4594 4593 4593 4592 4592 4592 4589 4591 4589 4589
4593 4593 4593 4594 4594 4594 4593 4593 4592 4592 4592 4593 4598 4598 4598
4594 4594 4593 4593 4595 4594 4594 4594 4592 4592 4592 4593 4598 4598 4598
4595 4595 4593 4596 4594 4597 4594 4595 4592 4592 4592 4589 4598 4598 4598
4593 4593 4594 4594 4594 4594 4594 4593 4592 4592 4592 4590 4598 4598 4598

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 4593 bytes 100%
1,000 4590 bytes -3 bytes 100%
10,000 4589 bytes -1 byte 100%
100,000 4589 bytes 4.35%
1,000,000 4589 bytes 0.29%
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
4595 bytes +6 bytes (+0.13%)
4595 bytes +6 bytes (+0.13%)
4607 bytes +18 bytes (+0.39%) +12 bytes
4639 bytes +50 bytes (+1.09%) +44 bytes
4663 bytes +74 bytes (+1.61%) +68 bytes
4697 bytes +108 bytes (+2.35%) +102 bytes
4724 bytes +135 bytes (+2.94%) +129 bytes
4757 bytes +168 bytes (+3.66%) +162 bytes
4787 bytes +198 bytes (+4.31%) +192 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 4126 bytes -463 bytes (-10.09%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 4216 bytes -373 bytes (-8.13%)
Zstandard (Wikipedia) zstd zstd -19 4579 bytes -10 bytes (-0.22%)
LZMA2 (Wikipedia) xz xz -9 4632 bytes +43 bytes (+0.94%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 4736 bytes +147 bytes (+3.20%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 4740 bytes +151 bytes (+3.29%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 5015 bytes +426 bytes (+9.28%)

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