Choose a version:
20% The original file has 598400 bytes (584.4k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 120732 bytes (117.9k, 20%).

After GZIP compression these minified files vary in size:
Boot
  42706 bytes (41.7k)
CDN
cdnjs
  36446 bytes (35.6k)
CDN
gzip -6 (default)
  36109 bytes (35.3k)
local copy
cdnhttps
  36089 bytes (35.2k)
CDN
unpkg
  36067 bytes (35.2k)
CDN
jsdelivr
  35982 bytes (35.1k)
CDN
gzip -9
  35927 bytes (35.1k)
local copy
libdeflate -12
  34797 bytes (34.0k)
local copy
7zip -mx=9 -tgzip
  34777 bytes (34.0k)
local copy
kzip -s0 -rn -b1
  34771 bytes (34.0k)
local copy
pigz -11 -n
  34680 bytes (33.9k)
local copy
Zopfli
  34647 bytes (33.8k)
local copy
Zopfli (defluff)
  34646 bytes (33.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.13.0.min.js (or via HTTPS)

You will automatically get the smallest React 0.13.0 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 1335 bytes by using my React 0.13.0 Zopfli version instead of the best available CDN (3.85% smaller than jsdelivr, 34647 vs. 35982 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 --mls16 --bsr14 --lazy --ohh

(found December 16, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 16  --mls16
block splitting recursion 14  --bsr14
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 (34646 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed https://fb.me/react-0.13.0.min.js --location | md5sum
3637ed039dbe5013c9d523262e8602a6  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.13.0.min.zopfli.js.gz | md5sum
3637ed039dbe5013c9d523262e8602a6  -

SHA1:
curl --silent --compressed https://fb.me/react-0.13.0.min.js --location | sha1sum
abe260949b842524c4f93a51d48773ca6f7e4012  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.13.0.min.zopfli.js.gz | sha1sum
abe260949b842524c4f93a51d48773ca6f7e4012  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 42706 bytes 3637ed039dbe5013c9d523262e8602a6 March 20, 2015 @ 16:51
cdnjs 36446 bytes 3637ed039dbe5013c9d523262e8602a6 March 11, 2015 @ 11:00
cdnhttps 36089 bytes 3637ed039dbe5013c9d523262e8602a6 December 24, 2015 @ 07:35
unpkg 36067 bytes 3637ed039dbe5013c9d523262e8602a6 July 11, 2016 @ 15:33
jsdelivr 35982 bytes 3637ed039dbe5013c9d523262e8602a6 March 10, 2015 @ 23:11

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
34647 bytes -2 bytes zopfli --i100000 --mls16 --bsr14 --lazy --ohh December 16, 2015 @ 13:22
34649 bytes -1 byte zopfli --i10000 --mls16 --bsr14 --lazy --ohh September 20, 2015 @ 17:21
34650 bytes -1 byte zopfli --i10000 --mls16 --bsr12 --lazy --ohh September 20, 2015 @ 16:28
34651 bytes -2 bytes zopfli --i10000 --mls4096 --bsr11 --lazy --ohh September 15, 2015 @ 18:42
34653 bytes -4 bytes zopfli --i1000 --mls4096 --bsr11 --lazy --ohh September 14, 2015 @ 15:13
34657 bytes -2 bytes zopfli --i1000 --mls4096 --bsr7 --lazy --ohh September 14, 2015 @ 14:38
34659 bytes zopfli --i100 --mls4096 --bsr11 --lazy --ohh September 14, 2015 @ 12:50

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
34677 34678 34676 34677 34677 34678 34679 34685 34682 34686 34689 34670 34669 34653 34682
34678 34661 34667 34683 34665 34670 34677 34679 34670 34670 34670 34671 34675 34682 34678
34662 34675 34664 34648 34674 34673 34671 34674 34666 34669 34670 34655 34675 34660 34654
34662 34663 34663 34659 34676 34657 34674 34677 34668 34670 34668 34655 34675 34677 34677
34670 34673 34663 34676 34672 34674 34674 34674 34674 34673 34667 34670 34676 34676 34675
34668 34670 34668 34670 34673 34670 34672 34673 34668 34670 34673 34654 34676 34677 34676
34669 34670 34670 34670 34674 34670 34668 34669 34668 34670 34668 34670 34677 34677 34677
34668 34669 34670 34670 34673 34670 34668 34669 34668 34670 34668 34647 34675 34649 34675
34670 34672 34675 34647 34673 34670 34668 34669 34666 34668 34668 34669 34676 34677 34678
34674 34670 34673 34678 34674 34670 34672 34670 34666 34670 34668 34670 34677 34655 34676
34669 34662 34664 34647 34647 34670 34671 34669 34666 34670 34670 34655 34677 34655 34654
34675 34675 34664 34647 34669 34670 34671 34670 34668 34670 34669 34669 34675 34655 34656
34672 34673 34674 34671 34671 34670 34671 34669 34668 34670 34668 34656 34677 34677 34677
34673 34673 34669 34670 34669 34670 34672 34669 34666 34670 34668 34670 34676 34651 34675
34663 34675 34670 34670 34673 34670 34671 34669 34668 34670 34668 34670 34654 34677 34677
34675 34674 34670 34670 34673 34670 34671 34669 34666 34670 34668 34654 34676 34677 34677
34675 34672 34670 34670 34670 34670 34672 34669 34668 34669 34668 34654 34676 34654 34676
34673 34673 34667 34661 34671 34670 34668 34669 34668 34669 34669 34653 34675 34654 34653
34668 34670 34669 34671 34670 34670 34673 34670 34666 34668 34668 34670 34676 34676 34678
34658 34670 34664 34670 34674 34674 34669 34669 34668 34668 34668 34670 34675 34654 34653
34659 34668 34668 34670 34673 34673 34668 34669 34668 34670 34673 34670 34657 34675 34676
34673 34673 34665 34670 34673 34670 34672 34669 34666 34670 34668 34669 34656 34675 34675
34673 34670 34670 34670 34673 34673 34672 34669 34668 34670 34668 34669 34676 34675 34675

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 34659 bytes 100%
1,000 34651 bytes -8 bytes 100%
10,000 34649 bytes -2 bytes 100%
100,000 34647 bytes -2 bytes 2.32%
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
34775 bytes +128 bytes (+0.37%) +4 bytes
34771 bytes +124 bytes (+0.36%)
34796 bytes +149 bytes (+0.43%) +25 bytes
34806 bytes +159 bytes (+0.46%) +35 bytes
34806 bytes +159 bytes (+0.46%) +35 bytes
34837 bytes +190 bytes (+0.55%) +66 bytes
34835 bytes +188 bytes (+0.54%) +64 bytes
34877 bytes +230 bytes (+0.66%) +106 bytes
34882 bytes +235 bytes (+0.68%) +111 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 25746 bytes -8901 bytes (-25.69%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 27471 bytes -7176 bytes (-20.71%)
Brotli (Wikipedia) brotli brotli -q 11 30712 bytes -3935 bytes (-11.36%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 30736 bytes -3911 bytes (-11.29%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 31014 bytes -3633 bytes (-10.49%)
LZMA2 (Wikipedia) xz xz -9 31768 bytes -2879 bytes (-8.31%)
Zstandard (Wikipedia) zstd zstd -19 33139 bytes -1508 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