Choose a version:
20% The original file has 549985 bytes (537.1k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 112351 bytes (109.7k, 20%).

After GZIP compression these minified files vary in size:
Boot
  37549 bytes (36.7k)
CDN
Baidu
  31584 bytes (30.8k)
CDN
cdnjs
  31572 bytes (30.8k)
CDN
gzip -6 (default)
  31121 bytes (30.4k)
local copy
cdnhttps
  31101 bytes (30.4k)
CDN
jsdelivr
  31006 bytes (30.3k)
CDN
gzip -9
  30969 bytes (30.2k)
local copy
7zip -mx=9 -tgzip
  29990 bytes (29.3k)
local copy
libdeflate -12
  29956 bytes (29.3k)
local copy
kzip -s0 -rn -b5
  29901 bytes (29.2k)
local copy
pigz -11 -n
  29898 bytes (29.2k)
local copy
Zopfli
  29858 bytes (29.2k)
local copy
Zopfli (defluff)
  29857 bytes (29.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.10.0.min.js (or via HTTPS)

You will automatically get the smallest React 0.10.0 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 1148 bytes by using my React 0.10.0 Zopfli version instead of the best available CDN (3.84% smaller than jsdelivr, 29858 vs. 31006 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 --mls2 --bsr17 --lazy --ohh

(found October 21, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 2  --mls2
block splitting recursion 17  --bsr17
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 (29857 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed https://fb.me/react-0.10.0.min.js --location | md5sum
ccee8e983b9a380e27ebc9b112d1f4c9  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.10.0.min.zopfli.js.gz | md5sum
ccee8e983b9a380e27ebc9b112d1f4c9  -

SHA1:
curl --silent --compressed https://fb.me/react-0.10.0.min.js --location | sha1sum
c21e60147b4e6d7c35976476dc634aa1bd88b75f  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.10.0.min.zopfli.js.gz | sha1sum
c21e60147b4e6d7c35976476dc634aa1bd88b75f  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 37549 bytes ccee8e983b9a380e27ebc9b112d1f4c9 March 20, 2015 @ 16:46
cdnjs 31572 bytes ccee8e983b9a380e27ebc9b112d1f4c9 March 21, 2014 @ 23:45
cdnhttps 31101 bytes ccee8e983b9a380e27ebc9b112d1f4c9 December 24, 2015 @ 07:35
jsdelivr 31006 bytes ccee8e983b9a380e27ebc9b112d1f4c9 August 7, 2014 @ 20:33

And some CDNs send you a different file: original/react/react-0.10.0.min.js.gz not found
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp

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
29858 bytes -1 byte zopfli --i100000 --mls2 --bsr17 --lazy --ohh October 21, 2015 @ 14:28
29859 bytes -3 bytes zopfli --i10000 --mls2 --bsr17 --lazy --ohh October 21, 2015 @ 13:43
29862 bytes -4 bytes zopfli --i10000 --mls4 --bsr18 --lazy --ohh October 14, 2015 @ 09:37
29866 bytes -1 byte zopfli --i1000 --mls2 --bsr17 --lazy --ohh September 24, 2015 @ 00:46
29867 bytes -2 bytes zopfli --i100000 --mls8192 --bsr11 --lazy --ohh September 16, 2015 @ 12:07
29869 bytes -5 bytes zopfli --i10000 --mls8192 --bsr11 --lazy --ohh September 16, 2015 @ 11:26
29874 bytes -3 bytes zopfli --i1000 --mls8192 --bsr11 --lazy --ohh September 14, 2015 @ 20:35
29877 bytes -1 byte zopfli --i1000 --mls256 --bsr12 --lazy --ohh September 14, 2015 @ 20:19
29878 bytes -1 byte zopfli --i1000 --mls128 --bsr14 --lazy --ohh September 14, 2015 @ 20:12
29879 bytes zopfli --i100 --mls512 --bsr8 --lazy --ohh September 14, 2015 @ 12:04

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

Most recent activity on June 16, 2016 @ 14:39.

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
29888 29890 29888 29888 29888 29888 29887 29887 29886 29886 29886 29897 29896 29900 29898
29883 29882 29886 29888 29888 29889 29886 29887 29883 29884 29884 29888 29891 29900 29897
29887 29883 29889 29885 29886 29887 29887 29887 29884 29885 29892 29891 29894 29891 29891
29883 29873 29890 29876 29882 29886 29875 29882 29883 29884 29887 29876 29895 29891 29890
29869 29879 29876 29885 29890 29890 29882 29879 29873 29875 29882 29896 29896 29899 29891
29882 29879 29879 29879 29879 29874 29887 29878 29878 29874 29887 29886 29896 29892 29890
29882 29878 29877 29872 29877 29879 29879 29878 29877 29884 29887 29886 29894 29891 29890
29879 29879 29878 29878 29878 29876 29875 29886 29879 29885 29887 29875 29867 29902 29890
29882 29869 29883 29876 29879 29877 29875 29875 29883 29883 29880 29877 29897 29895 29892
29875 29873 29877 29876 29880 29877 29873 29887 29884 29884 29886 29899 29875 29892 29897
29869 29877 29877 29876 29881 29875 29876 29874 29883 29877 29887 29875 29878 29902 29891
29881 29875 29891 29872 29879 29877 29875 29875 29883 29884 29871 29878 29894 29894 29892
29880 29881 29876 29875 29888 29880 29875 29883 29885 29877 29886 29876 29877 29891 29891
29858 29860 29878 29879 29881 29877 29875 29883 29876 29876 29887 29893 29875 29897 29890
29875 29859 29874 29878 29879 29881 29874 29877 29883 29877 29881 29876 29894 29904 29890
29881 29860 29877 29876 29879 29874 29877 29883 29883 29883 29886 29887 29897 29900 29891
29881 29860 29879 29879 29880 29871 29875 29877 29882 29884 29887 29887 29895 29901 29891
29879 29873 29874 29876 29880 29877 29883 29875 29876 29884 29887 29876 29895 29895 29891
29880 29876 29877 29872 29879 29876 29877 29873 29877 29875 29887 29887 29895 29899 29891
29881 29877 29875 29874 29880 29875 29875 29883 29875 29884 29887 29887 29895 29893 29893
29883 29881 29873 29874 29882 29880 29875 29884 29883 29876 29886 29877 29895 29897 29891
29880 29878 29877 29860 29878 29880 29875 29881 29883 29884 29887 29886 29897 29896 29890
29865 29877 29871 29879 29879 29877 29875 29876 29877 29883 29887 29875 29894 29888 29891

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 29872 bytes 100%
1,000 29866 bytes -6 bytes 100%
10,000 29859 bytes -7 bytes 100%
100,000 29858 bytes -1 byte 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
29959 bytes +101 bytes (+0.34%) +58 bytes
29961 bytes +103 bytes (+0.34%) +60 bytes
29979 bytes +121 bytes (+0.41%) +78 bytes
29982 bytes +124 bytes (+0.42%) +81 bytes
29977 bytes +119 bytes (+0.40%) +76 bytes
29901 bytes +43 bytes (+0.14%)
29912 bytes +54 bytes (+0.18%) +11 bytes
29947 bytes +89 bytes (+0.30%) +46 bytes
29941 bytes +83 bytes (+0.28%) +40 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 22375 bytes -7483 bytes (-25.06%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 23341 bytes -6517 bytes (-21.83%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 26367 bytes -3491 bytes (-11.69%)
Brotli (Wikipedia) brotli brotli -q 11 26577 bytes -3281 bytes (-10.99%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 26677 bytes -3181 bytes (-10.65%)
LZMA2 (Wikipedia) xz xz -9 27656 bytes -2202 bytes (-7.37%)
Zstandard (Wikipedia) zstd zstd -19 28532 bytes -1326 bytes (-4.44%)

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