Choose a version:
23% The original file has 571784 bytes (558.4k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 130436 bytes (127.4k, 23%).

After GZIP compression these minified files vary in size:
Boot
  43495 bytes (42.5k)
CDN
cdnjs
  36498 bytes (35.6k)
CDN
gzip -6 (default)
  36021 bytes (35.2k)
local copy
cdnhttps
  36001 bytes (35.2k)
CDN
unpkg
  35941 bytes (35.1k)
CDN
jsdelivr
  35865 bytes (35.0k)
CDN
gzip -9
  35838 bytes (35.0k)
local copy
7zip -mx=9 -tgzip
  34712 bytes (33.9k)
local copy
libdeflate -12
  34670 bytes (33.9k)
local copy
kzip -s0 -rn -b0
  34651 bytes (33.8k)
local copy
pigz -11 -n
  34595 bytes (33.8k)
local copy
Zopfli
  34582 bytes (33.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/react/react-0.12.2.min.js (or via HTTPS)

You will automatically get the smallest React 0.12.2 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 1283 bytes by using my React 0.12.2 Zopfli version instead of the best available CDN (3.71% smaller than jsdelivr, 34582 vs. 35865 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 --mls512 --bsr14 --lazy --ohh

(found December 16, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 512  --mls512
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

Verify file integrity

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

MD5:
curl --silent --compressed https://fb.me/react-0.12.2.min.js --location | md5sum
9d5e8e2d89dc08dedce3bbbd4dc15886  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.12.2.min.zopfli.js.gz | md5sum
9d5e8e2d89dc08dedce3bbbd4dc15886  -

SHA1:
curl --silent --compressed https://fb.me/react-0.12.2.min.js --location | sha1sum
93fa35574fcf76a7c0367d26ee5c9b54abdcc8ed  -
curl --silent --compressed https://minime.stephan-brumme.com/files/react/react-0.12.2.min.zopfli.js.gz | sha1sum
93fa35574fcf76a7c0367d26ee5c9b54abdcc8ed  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 43495 bytes 9d5e8e2d89dc08dedce3bbbd4dc15886 March 20, 2015 @ 16:51
cdnjs 36498 bytes 9d5e8e2d89dc08dedce3bbbd4dc15886 December 20, 2014 @ 07:00
cdnhttps 36001 bytes 9d5e8e2d89dc08dedce3bbbd4dc15886 December 24, 2015 @ 07:35
unpkg 35941 bytes 9d5e8e2d89dc08dedce3bbbd4dc15886 July 11, 2016 @ 15:34
jsdelivr 35865 bytes 9d5e8e2d89dc08dedce3bbbd4dc15886 December 18, 2014 @ 22:09

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
34582 bytes -2 bytes zopfli --i100000 --mls512 --bsr14 --lazy --ohh December 16, 2015 @ 15:42
34584 bytes -1 byte zopfli --i10000 --mls64 --bsr8 --lazy --ohh September 15, 2015 @ 20:33
34585 bytes -1 byte zopfli --i1000 --mls4096 --bsr13 --lazy --ohh September 14, 2015 @ 16:03
34586 bytes -1 byte zopfli --i1000 --mls512 --bsr8 --lazy --ohh September 14, 2015 @ 15:43
34587 bytes -1 byte zopfli --i1000 --mls64 --bsr8 --lazy --ohh September 14, 2015 @ 15:33
34588 bytes -1 byte zopfli --i1000 --mls64 --bsr7 --lazy --ohh September 14, 2015 @ 15:30
34589 bytes -3 bytes zopfli --i1000 --mls64 --bsr6 --lazy --ohh September 14, 2015 @ 15:29
34592 bytes zopfli --i100 --mls128 --bsr10 --lazy --ohh September 14, 2015 @ 12:02

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
34600 34599 34600 34602 34600 34601 34599 34601 34604 34604 34603 34612 34603 34600 34602
34607 34608 34605 34609 34597 34596 34596 34596 34598 34599 34598 34607 34597 34599 34595
34586 34586 34585 34587 34582 34585 34585 34585 34583 34585 34585 34585 34585 34596 34587
34586 34586 34600 34599 34587 34585 34586 34585 34586 34585 34586 34585 34587 34594 34586
34585 34586 34596 34601 34586 34582 34585 34586 34583 34594 34586 34585 34586 34587 34586
34586 34586 34597 34599 34587 34585 34587 34585 34586 34585 34586 34585 34585 34587 34586
34585 34586 34597 34600 34587 34586 34585 34587 34586 34585 34586 34597 34586 34586 34589
34586 34585 34598 34600 34587 34585 34585 34586 34586 34586 34586 34585 34586 34587 34599
34587 34587 34604 34603 34585 34585 34586 34585 34586 34587 34589 34583 34587 34588 34586
34586 34585 34603 34598 34586 34586 34587 34586 34585 34585 34590 34583 34586 34588 34588
34585 34586 34600 34600 34582 34585 34589 34586 34582 34585 34589 34585 34588 34587 34587
34589 34589 34600 34599 34587 34585 34589 34586 34586 34585 34590 34585 34586 34587 34588
34589 34585 34600 34601 34587 34586 34589 34586 34586 34585 34589 34585 34586 34587 34587
34586 34586 34596 34601 34587 34585 34585 34586 34585 34585 34589 34585 34586 34593 34587
34586 34586 34596 34599 34587 34585 34587 34586 34590 34585 34590 34583 34586 34603 34586
34585 34585 34597 34599 34587 34585 34585 34586 34586 34585 34590 34585 34586 34597 34586
34590 34588 34602 34602 34586 34586 34589 34585 34589 34586 34586 34585 34585 34603 34587
34589 34586 34597 34600 34586 34585 34586 34586 34585 34585 34589 34585 34586 34587 34585
34586 34588 34597 34601 34586 34587 34586 34585 34589 34585 34585 34585 34588 34587 34586
34585 34585 34603 34601 34587 34586 34587 34585 34590 34594 34589 34585 34588 34596 34587
34587 34587 34600 34590 34585 34585 34585 34585 34583 34587 34586 34585 34588 34587 34586
34586 34587 34595 34601 34585 34585 34587 34586 34582 34585 34589 34585 34586 34603 34586
34586 34586 34607 34600 34586 34585 34589 34586 34586 34594 34589 34585 34586 34597 34587

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 34592 bytes 100%
1,000 34585 bytes -7 bytes 100%
10,000 34584 bytes -1 byte 100%
100,000 34582 bytes -2 bytes 3.19%
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
34651 bytes +69 bytes (+0.20%)
34654 bytes +72 bytes (+0.21%) +3 bytes
34673 bytes +91 bytes (+0.26%) +22 bytes
34697 bytes +115 bytes (+0.33%) +46 bytes
34736 bytes +154 bytes (+0.45%) +85 bytes
34751 bytes +169 bytes (+0.49%) +100 bytes
34796 bytes +214 bytes (+0.62%) +145 bytes
34805 bytes +223 bytes (+0.64%) +154 bytes
34817 bytes +235 bytes (+0.68%) +166 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 25546 bytes -9036 bytes (-26.13%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 26801 bytes -7781 bytes (-22.50%)
Brotli (Wikipedia) brotli brotli -q 11 30648 bytes -3934 bytes (-11.38%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 30673 bytes -3909 bytes (-11.30%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 30901 bytes -3681 bytes (-10.64%)
LZMA2 (Wikipedia) xz xz -9 31808 bytes -2774 bytes (-8.02%)
Zstandard (Wikipedia) zstd zstd -19 32811 bytes -1771 bytes (-5.12%)

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