Choose a version:
20% The original file has 598504 bytes (584.5k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 120797 bytes (118.0k, 20%).

After GZIP compression these minified files vary in size:
Boot
  42730 bytes (41.7k)
CDN
cdnjs
  36465 bytes (35.6k)
CDN
gzip -6 (default)
  36122 bytes (35.3k)
local copy
cdnhttps
  36102 bytes (35.3k)
CDN
unpkg
  36081 bytes (35.2k)
CDN
jsdelivr
  35997 bytes (35.2k)
CDN
gzip -9
  35943 bytes (35.1k)
local copy
libdeflate -12
  34814 bytes (34.0k)
local copy
kzip -s0 -rn -b1
  34786 bytes (34.0k)
local copy
7zip -mx=9 -tgzip
  34783 bytes (34.0k)
local copy
pigz -11 -n
  34693 bytes (33.9k)
local copy
Zopfli
  34660 bytes (33.8k)
local copy
Zopfli (defluff)
  34659 bytes (33.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.13.1.min.js (or via HTTPS)

You will automatically get the smallest React 0.13.1 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 1337 bytes by using my React 0.13.1 Zopfli version instead of the best available CDN (3.86% smaller than jsdelivr, 34660 vs. 35997 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 --mls8 --bsr15 --lazy --ohh

(found December 16, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 8  --mls8
block splitting recursion 15  --bsr15
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

Even Smaller Files Thanks To Defluff

Zopfli's output can be further optimized by the defluff tool.
In this particular case, defluff saves 1 more byte (34659 bytes).

Verify file integrity

After decompression, my uncompressed files are identical to the original ones:

MD5:
curl --silent --compressed https://fb.me/react-0.13.1.min.js --location | md5sum
26b22e016cbe907215a04dbf03707622  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.13.1.min.zopfli.js.gz | md5sum
26b22e016cbe907215a04dbf03707622  -

SHA1:
curl --silent --compressed https://fb.me/react-0.13.1.min.js --location | sha1sum
918a2d557040525546c616eb4a0068120920a91e  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.13.1.min.zopfli.js.gz | sha1sum
918a2d557040525546c616eb4a0068120920a91e  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 42730 bytes 26b22e016cbe907215a04dbf03707622 March 20, 2015 @ 16:55
cdnjs 36465 bytes 26b22e016cbe907215a04dbf03707622 March 17, 2015 @ 13:30
cdnhttps 36102 bytes 26b22e016cbe907215a04dbf03707622 December 24, 2015 @ 07:35
unpkg 36081 bytes 26b22e016cbe907215a04dbf03707622 July 11, 2016 @ 15:33
jsdelivr 35997 bytes 26b22e016cbe907215a04dbf03707622 March 17, 2015 @ 01:11

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

Other Versions

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

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
34660 bytes -3 bytes zopfli --i100000 --mls8 --bsr15 --lazy --ohh December 16, 2015 @ 12:34
34663 bytes -2 bytes zopfli --i10000 --mls8192 --bsr10 --lazy --ohh September 15, 2015 @ 12:41
34665 bytes -4 bytes zopfli --i1000 --mls8192 --bsr10 --lazy --ohh September 14, 2015 @ 14:08
34669 bytes -1 byte zopfli --i1000 --mls4096 --bsr7 --lazy --ohh September 14, 2015 @ 13:58
34670 bytes -6 bytes zopfli --i1000 --mls4096 --bsr6 --lazy --ohh September 14, 2015 @ 13:58
34676 bytes zopfli --i100 --mls4096 --bsr16 --lazy --ohh September 14, 2015 @ 12:00

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
34692 34692 34693 34692 34692 34692 34694 34699 34699 34701 34702 34685 34691 34669 34697
34698 34674 34683 34698 34680 34686 34693 34694 34684 34685 34683 34686 34691 34697 34696
34681 34685 34672 34685 34690 34689 34688 34685 34685 34684 34685 34669 34690 34670 34691
34677 34676 34662 34674 34690 34688 34689 34690 34683 34683 34685 34668 34692 34692 34692
34688 34689 34661 34689 34673 34691 34689 34685 34689 34689 34685 34685 34692 34692 34692
34684 34685 34685 34685 34689 34684 34688 34690 34683 34684 34685 34669 34691 34692 34692
34684 34685 34685 34684 34689 34684 34684 34684 34685 34683 34686 34685 34663 34694 34692
34683 34684 34685 34684 34689 34684 34684 34685 34683 34683 34685 34669 34690 34693 34691
34687 34687 34672 34667 34689 34684 34683 34685 34685 34683 34685 34684 34668 34693 34692
34687 34683 34689 34685 34688 34684 34688 34685 34684 34683 34683 34685 34692 34668 34668
34676 34680 34661 34683 34675 34684 34688 34684 34685 34683 34685 34668 34692 34669 34668
34690 34690 34660 34678 34685 34684 34688 34684 34685 34683 34686 34670 34691 34668 34668
34689 34687 34688 34685 34688 34683 34688 34685 34683 34685 34685 34669 34689 34692 34668
34688 34688 34685 34685 34685 34684 34688 34685 34683 34685 34685 34671 34691 34668 34668
34688 34690 34685 34685 34688 34683 34688 34688 34683 34685 34685 34684 34666 34693 34692
34689 34687 34685 34685 34688 34683 34688 34688 34683 34684 34685 34669 34692 34693 34692
34684 34683 34685 34685 34684 34684 34689 34689 34685 34683 34685 34669 34690 34668 34668
34691 34685 34673 34678 34674 34684 34684 34684 34685 34683 34686 34685 34693 34693 34692
34683 34685 34684 34686 34685 34684 34688 34685 34686 34688 34688 34685 34693 34691 34691
34674 34682 34685 34684 34688 34689 34684 34684 34683 34684 34683 34685 34692 34669 34669
34673 34683 34683 34685 34689 34685 34682 34684 34686 34685 34685 34668 34690 34692 34692
34688 34685 34661 34685 34688 34684 34688 34684 34684 34683 34685 34684 34693 34692 34669
34689 34682 34685 34685 34688 34683 34688 34684 34684 34683 34685 34669 34692 34669 34669

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 34674 bytes 100%
1,000 34664 bytes -10 bytes 100%
10,000 34663 bytes -1 byte 100%
100,000 34660 bytes -3 bytes 2.03%
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
34789 bytes +129 bytes (+0.37%) +3 bytes
34786 bytes +126 bytes (+0.36%)
34812 bytes +152 bytes (+0.44%) +26 bytes
34824 bytes +164 bytes (+0.47%) +38 bytes
34825 bytes +165 bytes (+0.48%) +39 bytes
34852 bytes +192 bytes (+0.55%) +66 bytes
34852 bytes +192 bytes (+0.55%) +66 bytes
34891 bytes +231 bytes (+0.67%) +105 bytes
34898 bytes +238 bytes (+0.69%) +112 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 25755 bytes -8905 bytes (-25.69%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 27482 bytes -7178 bytes (-20.71%)
Brotli (Wikipedia) brotli brotli -q 11 30725 bytes -3935 bytes (-11.35%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 30790 bytes -3870 bytes (-11.17%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 31024 bytes -3636 bytes (-10.49%)
LZMA2 (Wikipedia) xz xz -9 31764 bytes -2896 bytes (-8.36%)
Zstandard (Wikipedia) zstd zstd -19 33151 bytes -1509 bytes (-4.35%)

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