Choose a version:
20% The original file has 600572 bytes (586.5k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 121738 bytes (118.9k, 20%).

After GZIP compression these minified files vary in size:
Boot
  42906 bytes (41.9k)
CDN
cdnjs
  36643 bytes (35.8k)
CDN
gzip -6 (default)
  36228 bytes (35.4k)
local copy
unpkg
  36212 bytes (35.4k)
CDN
cdnhttps
  36208 bytes (35.4k)
CDN
jsdelivr
  36151 bytes (35.3k)
CDN
gzip -9
  36057 bytes (35.2k)
local copy
7zip -mx=9 -tgzip
  34900 bytes (34.1k)
local copy
libdeflate -12
  34893 bytes (34.1k)
local copy
kzip -s0 -rn -b1
  34891 bytes (34.1k)
local copy
pigz -11 -n
  34810 bytes (34.0k)
local copy
Zopfli
  34774 bytes (34.0k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.13.3.min.js

You will automatically get the smallest React 0.13.3 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 1377 bytes by using my React 0.13.3 Zopfli version instead of the best available CDN (3.96% smaller than jsdelivr, 34774 vs. 36151 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 --i1000000 --mb8 --mls8192 --bsr22 --lazy --ohh

(found September 28, 2015)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 8192  --mls8192
block splitting recursion 22  --bsr22
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-0.13.3.min.js --location | md5sum
c3b6b1bdf51c9ef4ba3473a2e1dcb83a  -
curl --silent --compressed http://minime.stephan-brumme.com/files/react/react-0.13.3.min.zopfli.js.gz | md5sum
c3b6b1bdf51c9ef4ba3473a2e1dcb83a  -

SHA1:
curl --silent --compressed https://fb.me/react-0.13.3.min.js --location | sha1sum
7fe6bacb25ba95c4e6494e124853c2a870bfc038  -
curl --silent --compressed http://minime.stephan-brumme.com/files/react/react-0.13.3.min.zopfli.js.gz | sha1sum
7fe6bacb25ba95c4e6494e124853c2a870bfc038  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 42906 bytes c3b6b1bdf51c9ef4ba3473a2e1dcb83a May 14, 2015 @ 23:23
cdnjs 36643 bytes c3b6b1bdf51c9ef4ba3473a2e1dcb83a May 13, 2015 @ 10:45
unpkg 36212 bytes c3b6b1bdf51c9ef4ba3473a2e1dcb83a July 11, 2016 @ 15:33
cdnhttps 36208 bytes c3b6b1bdf51c9ef4ba3473a2e1dcb83a December 24, 2015 @ 07:35
jsdelivr 36151 bytes c3b6b1bdf51c9ef4ba3473a2e1dcb83a May 9, 2015 @ 01:43

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

Other Versions

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

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
34774 bytes -1 byte zopfli --i1000000 --mls8192 --bsr22 --lazy --ohh September 28, 2015 @ 15:44
34775 bytes -1 byte zopfli --i10000000 --mls8192 --bsr13 --lazy --ohh September 17, 2015 @ 07:58
34776 bytes -2 bytes zopfli --i1000000 --mls8192 --bsr13 --lazy --ohh September 14, 2015 @ 21:36
34778 bytes -3 bytes zopfli --i100000 --mls8192 --bsr13 --lazy --ohh September 14, 2015 @ 14:26
34781 bytes -1 byte zopfli --i10000 --mls8192 --bsr13 --lazy --ohh September 14, 2015 @ 13:09
34782 bytes -8 bytes zopfli --i1000 --mls8192 --bsr13 --lazy --ohh September 14, 2015 @ 12:56
34790 bytes zopfli --i100 --mls8192 --bsr13 --lazy --ohh September 14, 2015 @ 11:51

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, 100,000, 1,000,000 or 10,000,000.
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
34807 34809 34808 34806 34808 34810 34811 34812 34814 34814 34794 34795 34792 34805 34806
34814 34809 34806 34785 34802 34803 34804 34799 34798 34798 34797 34798 34810 34811 34783
34806 34800 34800 34797 34800 34801 34796 34796 34799 34796 34798 34795 34803 34806 34785
34806 34796 34801 34798 34798 34797 34802 34802 34802 34798 34798 34803 34783 34806 34787
34807 34804 34800 34800 34800 34796 34802 34799 34795 34796 34798 34786 34787 34804 34800
34807 34798 34797 34797 34797 34797 34797 34799 34796 34798 34799 34795 34780 34805 34804
34806 34802 34800 34800 34801 34797 34797 34796 34796 34801 34798 34790 34804 34804 34791
34806 34800 34800 34800 34801 34800 34801 34797 34796 34796 34798 34794 34805 34777 34784
34800 34801 34810 34799 34800 34800 34797 34797 34797 34798 34796 34798 34803 34809 34783
34806 34800 34800 34798 34802 34800 34797 34796 34795 34798 34798 34797 34775 34809 34798
34807 34800 34800 34797 34800 34800 34797 34797 34796 34798 34798 34798 34779 34803 34787
34806 34800 34800 34799 34796 34796 34796 34797 34796 34798 34798 34788 34780 34806 34808
34807 34800 34800 34798 34798 34796 34797 34799 34798 34798 34798 34794 34780 34804 34790
34807 34800 34798 34800 34798 34796 34796 34796 34798 34798 34798 34794 34804 34792 34789
34807 34800 34796 34797 34800 34800 34799 34799 34795 34798 34798 34779 34780 34790 34791
34809 34800 34800 34797 34798 34800 34796 34799 34796 34798 34798 34789 34779 34777 34791
34810 34800 34797 34797 34801 34797 34796 34795 34799 34799 34796 34791 34804 34778 34781
34799 34797 34796 34797 34801 34797 34797 34797 34796 34798 34796 34796 34776 34777 34790
34806 34797 34796 34800 34798 34796 34796 34801 34796 34798 34796 34795 34774 34804 34786
34805 34800 34801 34797 34800 34801 34801 34799 34796 34798 34797 34795 34805 34803 34803
34805 34800 34800 34801 34798 34796 34800 34797 34796 34798 34798 34795 34786 34805 34806
34806 34800 34797 34798 34798 34796 34796 34797 34796 34798 34799 34785 34788 34804 34780
34809 34797 34797 34797 34800 34797 34797 34797 34796 34798 34798 34797 34780 34805 34807

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 34790 bytes 100%
1,000 34781 bytes -9 bytes 100%
10,000 34780 bytes -1 byte 100%
100,000 34775 bytes -5 bytes 4.93%
1,000,000 34774 bytes -1 byte 0.87%
10,000,000 34774 bytes 0.58%

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
34895 bytes +121 bytes (+0.35%) +4 bytes
34891 bytes +117 bytes (+0.34%)
34914 bytes +140 bytes (+0.40%) +23 bytes
34926 bytes +152 bytes (+0.44%) +35 bytes
34934 bytes +160 bytes (+0.46%) +43 bytes
34958 bytes +184 bytes (+0.53%) +67 bytes
34949 bytes +175 bytes (+0.50%) +58 bytes
34995 bytes +221 bytes (+0.64%) +104 bytes
34994 bytes +220 bytes (+0.63%) +103 bytes

Non-DEFLATE Algorithms

Archivers based on completely different compression algorithms often produce superior results.
Unfortunately, browsers only support gzip compression at the moment.
Algorithm Program Parameters Size Compared To Best Zopfli
ZPAQ (Wikipedia) zpaq zpaq -method 69 25838 bytes -8936 bytes (-25.70%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 27565 bytes -7209 bytes (-20.73%)
Brotli (Wikipedia) brotli brotli -q 11 30789 bytes -3985 bytes (-11.46%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 30980 bytes -3794 bytes (-10.91%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 31143 bytes -3631 bytes (-10.44%)
LZMA2 (Wikipedia) xz xz -9 31904 bytes -2870 bytes (-8.25%)
ZSTD (Wikipedia) zstd zstd -19 33235 bytes -1539 bytes (-4.43%)

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