Choose a version:
29% The original file has 434041 bytes (423.9k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 126490 bytes (123.5k, 29%).

After GZIP compression these minified files vary in size:
Boot
  42210 bytes (41.2k)
CDN
cdnjs
  35401 bytes (34.6k)
CDN
gzip -6 (default)
  34874 bytes (34.1k)
local copy
cdnhttps
  34854 bytes (34.0k)
CDN
unpkg
  34756 bytes (33.9k)
CDN
jsdelivr
  34706 bytes (33.9k)
CDN
gzip -9
  34663 bytes (33.9k)
local copy
7zip -mx=9 -tgzip
  33625 bytes (32.8k)
local copy
libdeflate -12
  33599 bytes (32.8k)
local copy
kzip -s0 -rn -b1
  33563 bytes (32.8k)
local copy
pigz -11 -n
  33498 bytes (32.7k)
local copy
Zopfli
  33482 bytes (32.7k)
local copy
Zopfli (defluff)
  33481 bytes (32.7k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.11.2.min.js (or via HTTPS)

You will automatically get the smallest React 0.11.2 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 1224 bytes by using my React 0.11.2 Zopfli version instead of the best available CDN (3.66% smaller than jsdelivr, 33482 vs. 34706 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 --mls1024 --bsr22 --lazy --ohh

(found December 18, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 1024  --mls1024
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

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 (33481 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed https://fb.me/react-0.11.2.min.js --location | md5sum
0cbcfcf774419b8037a1aef5e5c0ae71  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.11.2.min.zopfli.js.gz | md5sum
0cbcfcf774419b8037a1aef5e5c0ae71  -

SHA1:
curl --silent --compressed https://fb.me/react-0.11.2.min.js --location | sha1sum
a73e98b67a5f19fbf0c7eb01396efea50ab5b9c8  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.11.2.min.zopfli.js.gz | sha1sum
a73e98b67a5f19fbf0c7eb01396efea50ab5b9c8  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 42210 bytes 0cbcfcf774419b8037a1aef5e5c0ae71 (invalid)
cdnjs 35401 bytes 0cbcfcf774419b8037a1aef5e5c0ae71 (invalid)
cdnhttps 34854 bytes 0cbcfcf774419b8037a1aef5e5c0ae71 December 24, 2015 @ 07:35
unpkg 34756 bytes 0cbcfcf774419b8037a1aef5e5c0ae71 July 11, 2016 @ 15:34
jsdelivr 34706 bytes 0cbcfcf774419b8037a1aef5e5c0ae71 (invalid)

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
33482 bytes -1 byte zopfli --i100000 --mls1024 --bsr22 --lazy --ohh December 18, 2015 @ 20:14
33483 bytes -1 byte zopfli --i100000 --mls64 --bsr6 --lazy --ohh December 17, 2015 @ 13:29
33484 bytes -1 byte zopfli --i1000 --mls64 --bsr8 --lazy --ohh September 14, 2015 @ 17:50
33485 bytes -6 bytes zopfli --i1000 --mls64 --bsr9 --lazy --ohh September 14, 2015 @ 17:49
33491 bytes zopfli --i100 --mls64 --bsr14 --lazy --ohh September 14, 2015 @ 11:57

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
33490 33489 33490 33506 33487 33497 33489 33486 33484 33501 33485 33498 33505 33495 33492
33497 33496 33497 33498 33486 33486 33495 33484 33486 33489 33486 33485 33499 33499 33489
33495 33496 33493 33486 33486 33483 33485 33484 33487 33486 33485 33484 33489 33502 33491
33497 33498 33494 33485 33486 33483 33485 33484 33484 33484 33483 33484 33487 33495 33507
33494 33495 33493 33487 33484 33483 33486 33484 33484 33484 33483 33484 33488 33499 33489
33501 33500 33493 33485 33484 33485 33485 33502 33486 33485 33485 33485 33495 33499 33487
33494 33496 33493 33485 33486 33484 33485 33486 33484 33498 33485 33483 33499 33500 33489
33500 33500 33496 33497 33485 33483 33486 33484 33486 33486 33483 33484 33488 33500 33490
33495 33496 33494 33485 33484 33485 33485 33483 33485 33483 33486 33484 33496 33499 33489
33494 33495 33494 33486 33486 33484 33485 33485 33495 33484 33486 33485 33487 33499 33491
33499 33498 33494 33484 33486 33484 33485 33484 33485 33484 33483 33484 33488 33499 33492
33493 33492 33493 33485 33486 33484 33485 33486 33485 33483 33485 33484 33499 33495 33492
33494 33494 33492 33487 33486 33483 33485 33486 33484 33485 33485 33484 33501 33497 33488
33495 33498 33493 33486 33486 33485 33486 33484 33484 33485 33483 33484 33500 33495 33487
33495 33494 33492 33485 33486 33483 33485 33484 33484 33490 33483 33484 33496 33495 33489
33498 33498 33493 33485 33486 33483 33485 33484 33484 33485 33483 33484 33499 33495 33487
33497 33495 33495 33499 33486 33484 33485 33485 33486 33486 33483 33485 33490 33500 33489
33496 33496 33496 33486 33499 33484 33486 33485 33484 33484 33483 33484 33496 33499 33487
33498 33499 33497 33486 33484 33483 33485 33483 33485 33482 33483 33484 33490 33496 33493
33493 33493 33492 33486 33484 33484 33486 33485 33484 33484 33485 33485 33489 33497 33489
33495 33496 33494 33486 33486 33484 33485 33483 33486 33485 33483 33485 33499 33499 33503
33499 33501 33492 33486 33484 33483 33485 33485 33485 33486 33485 33482 33491 33489 33489
33495 33493 33492 33485 33486 33483 33485 33483 33484 33497 33483 33484 33496 33499 33486

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 33491 bytes 100%
1,000 33484 bytes -7 bytes 100%
10,000 33484 bytes 100%
100,000 33482 bytes -2 bytes 24.93%
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
33564 bytes +82 bytes (+0.24%) +1 byte
33563 bytes +81 bytes (+0.24%)
33578 bytes +96 bytes (+0.29%) +15 bytes
33607 bytes +125 bytes (+0.37%) +44 bytes
33649 bytes +167 bytes (+0.50%) +86 bytes
33663 bytes +181 bytes (+0.54%) +100 bytes
33625 bytes +143 bytes (+0.43%) +62 bytes
33662 bytes +180 bytes (+0.54%) +99 bytes
33675 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 24797 bytes -8685 bytes (-25.94%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 25941 bytes -7541 bytes (-22.52%)
Brotli (Wikipedia) brotli brotli -q 11 29579 bytes -3903 bytes (-11.66%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 29688 bytes -3794 bytes (-11.33%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 29728 bytes -3754 bytes (-11.21%)
LZMA2 (Wikipedia) xz xz -9 30852 bytes -2630 bytes (-7.85%)
Zstandard (Wikipedia) zstd zstd -19 31869 bytes -1613 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