Choose a version:
20% The original file has 599376 bytes (585.3k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 121458 bytes (118.6k, 20%).

After GZIP compression these minified files vary in size:
Boot
  42775 bytes (41.8k)
CDN
cdnjs
  36536 bytes (35.7k)
CDN
gzip -6 (default)
  36132 bytes (35.3k)
local copy
unpkg
  36115 bytes (35.3k)
CDN
cdnhttps
  36112 bytes (35.3k)
CDN
jsdelivr
  36056 bytes (35.2k)
CDN
gzip -9
  35961 bytes (35.1k)
local copy
7zip -mx=9 -tgzip
  34822 bytes (34.0k)
local copy
kzip -s0 -rn -b1
  34806 bytes (34.0k)
local copy
libdeflate -12
  34804 bytes (34.0k)
local copy
pigz -11 -n
  34724 bytes (33.9k)
local copy
Zopfli
  34689 bytes (33.9k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.13.2.min.js (or via HTTPS)

You will automatically get the smallest React 0.13.2 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 1367 bytes by using my React 0.13.2 Zopfli version instead of the best available CDN (3.94% smaller than jsdelivr, 34689 vs. 36056 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 --mls32768 --bsr19 --lazy --ohh

(found November 18, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 32768  --mls32768
block splitting recursion 19  --bsr19
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-0.13.2.min.js --location | md5sum
994ca2135869a3925df50d71bbde4c3d  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.13.2.min.zopfli.js.gz | md5sum
994ca2135869a3925df50d71bbde4c3d  -

SHA1:
curl --silent --compressed https://fb.me/react-0.13.2.min.js --location | sha1sum
11efe88a9507f1d6b81f5fd2911f8258a2472007  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.13.2.min.zopfli.js.gz | sha1sum
11efe88a9507f1d6b81f5fd2911f8258a2472007  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 42775 bytes 994ca2135869a3925df50d71bbde4c3d April 21, 2015 @ 06:08
cdnjs 36536 bytes 994ca2135869a3925df50d71bbde4c3d April 20, 2015 @ 09:30
unpkg 36115 bytes 994ca2135869a3925df50d71bbde4c3d July 11, 2016 @ 15:33
cdnhttps 36112 bytes 994ca2135869a3925df50d71bbde4c3d December 24, 2015 @ 07:35
jsdelivr 36056 bytes 994ca2135869a3925df50d71bbde4c3d April 19, 2015 @ 00:42

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

Other Versions

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

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
34689 bytes -3 bytes zopfli --i100000 --mls32768 --bsr19 --lazy --ohh November 18, 2015 @ 08:57
34692 bytes -2 bytes zopfli --i10000 --mls32768 --bsr10 --lazy --ohh September 15, 2015 @ 08:16
34694 bytes -5 bytes zopfli --i1000 --mls32768 --bsr10 --lazy --ohh September 14, 2015 @ 13:19
34699 bytes -1 byte zopfli --i1000 --mls8192 --bsr12 --lazy --ohh September 14, 2015 @ 13:15
34700 bytes -4 bytes zopfli --i1000 --mls4096 --bsr10 --lazy --ohh September 14, 2015 @ 13:13
34704 bytes zopfli --i100 --mls32768 --bsr10 --lazy --ohh September 14, 2015 @ 12:02

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

Most recent activity on July 11, 2016 @ 15:33.

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 100,000.
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
34722 34722 34722 34720 34720 34724 34725 34728 34728 34731 34712 34711 34722 34721 34722
34727 34721 34723 34703 34693 34719 34716 34718 34711 34711 34711 34713 34711 34726 34720
34723 34712 34711 34711 34711 34711 34711 34712 34710 34711 34711 34711 34719 34703 34718
34711 34713 34720 34711 34715 34709 34714 34712 34711 34715 34712 34710 34721 34721 34719
34728 34713 34711 34714 34712 34710 34710 34711 34711 34711 34710 34710 34709 34720 34717
34710 34713 34711 34711 34711 34711 34712 34711 34711 34711 34710 34710 34719 34720 34721
34722 34713 34711 34715 34715 34714 34710 34711 34712 34712 34711 34697 34710 34719 34689
34722 34713 34711 34711 34711 34711 34714 34712 34711 34711 34711 34699 34710 34705 34718
34718 34713 34711 34714 34715 34710 34714 34711 34712 34711 34712 34714 34698 34719 34720
34723 34713 34711 34714 34712 34714 34714 34711 34713 34711 34710 34710 34720 34718 34718
34724 34715 34711 34714 34712 34714 34710 34711 34711 34712 34712 34713 34713 34720 34697
34715 34715 34711 34714 34714 34709 34714 34712 34712 34711 34710 34712 34722 34721 34721
34726 34715 34711 34711 34713 34709 34714 34712 34711 34714 34712 34714 34692 34720 34693
34714 34715 34711 34711 34715 34711 34710 34711 34711 34711 34710 34712 34700 34718 34718
34723 34715 34711 34711 34711 34714 34710 34711 34711 34712 34712 34698 34720 34697 34692
34726 34715 34711 34711 34711 34714 34710 34711 34711 34711 34711 34710 34697 34721 34689
34715 34715 34711 34711 34716 34711 34710 34710 34711 34711 34710 34701 34721 34721 34722
34726 34713 34710 34713 34715 34710 34711 34711 34711 34711 34711 34710 34700 34698 34718
34713 34713 34712 34711 34711 34711 34709 34712 34711 34715 34711 34711 34720 34720 34720
34722 34712 34714 34712 34712 34710 34715 34712 34711 34711 34710 34711 34722 34720 34720
34723 34713 34715 34711 34711 34714 34714 34711 34711 34712 34710 34711 34720 34719 34721
34714 34713 34711 34714 34716 34711 34710 34711 34711 34712 34712 34710 34700 34719 34699
34726 34713 34715 34714 34712 34714 34710 34712 34712 34711 34712 34710 34721 34720 34697

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 34704 bytes 100%
1,000 34694 bytes -10 bytes 100%
10,000 34692 bytes -2 bytes 100%
100,000 34689 bytes -3 bytes 1.74%
1,000,000
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
34807 bytes +118 bytes (+0.34%) +1 byte
34806 bytes +117 bytes (+0.34%)
34826 bytes +137 bytes (+0.39%) +20 bytes
34842 bytes +153 bytes (+0.44%) +36 bytes
34855 bytes +166 bytes (+0.48%) +49 bytes
34845 bytes +156 bytes (+0.45%) +39 bytes
34870 bytes +181 bytes (+0.52%) +64 bytes
34876 bytes +187 bytes (+0.54%) +70 bytes
34885 bytes +196 bytes (+0.57%) +79 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
ZPAQ (Wikipedia) zpaq zpaq -method 69 25780 bytes -8909 bytes (-25.68%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 27490 bytes -7199 bytes (-20.75%)
Brotli (Wikipedia) brotli brotli -q 11 30732 bytes -3957 bytes (-11.41%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 30881 bytes -3808 bytes (-10.98%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 31089 bytes -3600 bytes (-10.38%)
LZMA2 (Wikipedia) xz xz -9 31824 bytes -2865 bytes (-8.26%)
Zstandard (Wikipedia) zstd zstd -19 33145 bytes -1544 bytes (-4.45%)

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 2018.
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