Choose a version:
21% The original file has 593628 bytes (579.7k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 126354 bytes (123.4k, 21%).

After GZIP compression these minified files vary in size:
Boot
  42185 bytes (41.2k)
CDN
cdnjs
  35345 bytes (34.5k)
CDN
gzip -6 (default)
  34826 bytes (34.0k)
local copy
cdnhttps
  34806 bytes (34.0k)
CDN
unpkg
  34709 bytes (33.9k)
CDN
jsdelivr
  34656 bytes (33.8k)
CDN
gzip -9
  34616 bytes (33.8k)
local copy
7zip -mx=9 -tgzip
  33584 bytes (32.8k)
local copy
libdeflate -12
  33562 bytes (32.8k)
local copy
kzip -s0 -rn -b1
  33523 bytes (32.7k)
local copy
pigz -11 -n
  33457 bytes (32.7k)
local copy
Zopfli
  33442 bytes (32.7k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.11.1.min.js (or via HTTPS)

You will automatically get the smallest React 0.11.1 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 1214 bytes by using my React 0.11.1 Zopfli version instead of the best available CDN (3.63% smaller than jsdelivr, 33442 vs. 34656 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 --mls128 --bsr16 --lazy --ohh

(found December 17, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 128  --mls128
block splitting recursion 16  --bsr16
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-0.11.1.min.js --location | md5sum
a9aa3f2390f73d1b7fa890db000d62cc  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.11.1.min.zopfli.js.gz | md5sum
a9aa3f2390f73d1b7fa890db000d62cc  -

SHA1:
curl --silent --compressed https://fb.me/react-0.11.1.min.js --location | sha1sum
526fac06935134b6e455d59e79efe24b55af8712  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.11.1.min.zopfli.js.gz | sha1sum
526fac06935134b6e455d59e79efe24b55af8712  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 42185 bytes a9aa3f2390f73d1b7fa890db000d62cc March 20, 2015 @ 16:48
cdnjs 35345 bytes a9aa3f2390f73d1b7fa890db000d62cc July 25, 2014 @ 21:00
cdnhttps 34806 bytes a9aa3f2390f73d1b7fa890db000d62cc December 24, 2015 @ 07:35
unpkg 34709 bytes a9aa3f2390f73d1b7fa890db000d62cc July 11, 2016 @ 15:34
jsdelivr 34656 bytes a9aa3f2390f73d1b7fa890db000d62cc August 7, 2014 @ 20:33

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
33442 bytes -1 byte zopfli --i100000 --mls128 --bsr16 --lazy --ohh December 17, 2015 @ 12:11
33443 bytes -1 byte zopfli --i10000 --mls128 --bsr16 --lazy --ohh September 17, 2015 @ 03:50
33444 bytes -1 byte zopfli --i1000 --mls64 --bsr13 --lazy --ohh September 14, 2015 @ 18:35
33445 bytes -8 bytes zopfli --i1000 --mls64 --bsr4 --lazy --ohh September 14, 2015 @ 18:32
33453 bytes zopfli --i100 --mls64 --bsr9 --lazy --ohh September 14, 2015 @ 12:03

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 @ 15:34.

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
33458 33461 33446 33457 33457 33457 33447 33445 33444 33462 33442 33458 33466 33463 33455
33456 33456 33457 33456 33459 33445 33458 33458 33445 33451 33445 33445 33458 33460 33448
33456 33460 33455 33457 33444 33445 33445 33445 33446 33444 33445 33444 33448 33462 33464
33478 33457 33455 33444 33444 33442 33444 33445 33444 33442 33443 33445 33460 33462 33463
33455 33460 33456 33458 33444 33445 33445 33444 33444 33458 33444 33444 33459 33460 33446
33459 33460 33454 33457 33444 33444 33444 33462 33443 33442 33444 33445 33456 33460 33449
33455 33458 33451 33454 33444 33444 33444 33457 33444 33444 33445 33444 33457 33460 33446
33460 33459 33455 33453 33445 33444 33443 33444 33443 33444 33444 33445 33447 33460 33451
33457 33456 33457 33456 33444 33445 33444 33445 33444 33457 33443 33444 33456 33460 33451
33457 33454 33454 33457 33444 33444 33444 33444 33456 33444 33445 33445 33456 33460 33447
33455 33458 33457 33457 33445 33442 33444 33445 33444 33444 33444 33445 33448 33460 33448
33455 33456 33453 33458 33444 33444 33444 33444 33444 33444 33443 33445 33460 33456 33446
33456 33458 33453 33453 33459 33444 33442 33444 33444 33444 33445 33445 33461 33460 33447
33460 33458 33455 33457 33445 33444 33444 33444 33444 33444 33444 33444 33460 33457 33446
33454 33461 33455 33456 33442 33444 33442 33443 33442 33458 33448 33444 33457 33456 33446
33459 33457 33453 33461 33456 33444 33444 33444 33444 33444 33443 33442 33456 33457 33449
33461 33458 33454 33462 33443 33445 33444 33445 33445 33444 33444 33445 33452 33460 33448
33456 33455 33454 33458 33444 33445 33445 33445 33444 33462 33443 33445 33457 33459 33447
33459 33459 33458 33458 33442 33445 33445 33445 33445 33444 33444 33445 33451 33458 33447
33459 33453 33453 33458 33445 33444 33444 33444 33444 33444 33444 33445 33447 33459 33447
33459 33457 33454 33460 33444 33444 33444 33443 33444 33444 33445 33445 33460 33460 33449
33458 33458 33453 33456 33442 33444 33445 33443 33444 33444 33442 33445 33451 33447 33447
33454 33455 33454 33457 33444 33444 33442 33444 33444 33457 33444 33445 33456 33460 33446

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 33453 bytes 100%
1,000 33444 bytes -9 bytes 100%
10,000 33443 bytes -1 byte 100%
100,000 33442 bytes -1 byte 8.70%
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
33524 bytes +82 bytes (+0.25%) +1 byte
33523 bytes +81 bytes (+0.24%)
33536 bytes +94 bytes (+0.28%) +13 bytes
33569 bytes +127 bytes (+0.38%) +46 bytes
33607 bytes +165 bytes (+0.49%) +84 bytes
33626 bytes +184 bytes (+0.55%) +103 bytes
33580 bytes +138 bytes (+0.41%) +57 bytes
33623 bytes +181 bytes (+0.54%) +100 bytes
33635 bytes +193 bytes (+0.58%) +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 24758 bytes -8684 bytes (-25.97%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 25897 bytes -7545 bytes (-22.56%)
Brotli (Wikipedia) brotli brotli -q 11 29597 bytes -3845 bytes (-11.50%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 29669 bytes -3773 bytes (-11.28%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 29688 bytes -3754 bytes (-11.23%)
LZMA2 (Wikipedia) xz xz -9 30808 bytes -2634 bytes (-7.88%)
Zstandard (Wikipedia) zstd zstd -19 31831 bytes -1611 bytes (-4.82%)

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