Choose a version:
48% The original file has 58533 bytes (57.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 27822 bytes (27.2k, 48%).

After GZIP compression these minified files vary in size:
Microsoft
  9494 bytes (9.3k)
CDN, direct link
Boot
  8671 bytes (8.5k)
CDN, direct link
MaxCDN
  8671 bytes (8.5k)
CDN, direct link
Baidu
  7336 bytes (7.2k)
CDN, direct link
cdnjs
  7329 bytes (7.2k)
CDN, direct link
gzip -6 (default)
  7306 bytes (7.1k)
local copy
gzip -9
  7288 bytes (7.1k)
local copy
cdnhttps
  7283 bytes (7.1k)
CDN, direct link
Yandex
  7273 bytes (7.1k)
CDN, direct link
jsdelivr
  7273 bytes (7.1k)
CDN, direct link
libdeflate -12
  7054 bytes (6.9k)
local copy
7zip -mx=9 -tgzip
  7045 bytes (6.9k)
local copy
kzip -s0 -rn -b1
  7038 bytes (6.9k)
local copy
pigz -11 -n
  7000 bytes (6.8k)
local copy
Zopfli
  6994 bytes (6.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.0.3.min.js

You will automatically get the smallest Bootstrap 3.0.3 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 279 bytes by using my Bootstrap 3.0.3 Zopfli version instead of the best available CDN (3.99% smaller than jsdelivr, 6994 vs. 7273 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 --bsr13 --lazy --ohh

(found November 23, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 1024  --mls1024
block splitting recursion 13  --bsr13
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://raw.githubusercontent.com/twbs/bootstrap/v3.0.3/dist/js/bootstrap.min.js --location | md5sum
353240ad37d1b084a53b1575f8ce57da  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.0.3.min.zopfli.js.gz | md5sum
353240ad37d1b084a53b1575f8ce57da  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.0.3/dist/js/bootstrap.min.js --location | sha1sum
b3182f99be238cc41164df8615005fad53282b4e  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.0.3.min.zopfli.js.gz | sha1sum
b3182f99be238cc41164df8615005fad53282b4e  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 9494 bytes 353240ad37d1b084a53b1575f8ce57da (invalid)
Boot 8671 bytes 353240ad37d1b084a53b1575f8ce57da (invalid)
MaxCDN 8671 bytes 353240ad37d1b084a53b1575f8ce57da (invalid)
cdnjs 7329 bytes 353240ad37d1b084a53b1575f8ce57da (invalid)
cdnhttps 7283 bytes 353240ad37d1b084a53b1575f8ce57da December 24, 2015 @ 07:36
Yandex 7273 bytes 353240ad37d1b084a53b1575f8ce57da (invalid)
jsdelivr 7273 bytes 353240ad37d1b084a53b1575f8ce57da (invalid)

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 7336 bytes ddf62d2a6b8d502890dca20f3eb20b81 only whitespaces differ (invalid)

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

Other Versions

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

3.3.7, 3.3.6, 3.3.5, 3.3.4, 3.3.2, 3.3.1, 3.3.0,
3.2.0,
3.1.1, 3.1.0,
3.0.3, 3.0.2, 3.0.1, 3.0.0

The project site contains an overview how well these versions were compressed.
Other interesting projects are AngularJS, BackboneJS, D3, Dojo, Ember, jQuery, Knockout, lodash, React, Socket.IO, ThreeJS, UnderscoreJS and Vue.

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
6994 bytes -1 byte zopfli --i100000 --mls1024 --bsr13 --lazy --ohh November 23, 2015 @ 15:33
6995 bytes -1 byte zopfli --i10000 --mls512 --bsr6 --lazy --ohh September 10, 2015 @ 18:50
6996 bytes -1 byte zopfli --i1000 --mls512 --bsr13 --lazy --ohh September 10, 2015 @ 16:51
6997 bytes zopfli --i100 --mls512 --bsr16 --lazy --ohh September 10, 2015 @ 16:27

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 @ 14:40.

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 1,000,000.
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
7011 7011 7010 7011 7011 7010 7011 7013 6998 7001 7000 6999 7000 6999 6998
7010 7010 7010 7009 7001 7009 7009 7000 6994 7000 7001 7001 7000 7001 7002
7009 7009 7010 7011 7001 7006 7000 7000 6994 7002 6999 6996 7000 6998 6999
7010 7010 7011 7010 7000 7000 7009 7000 6997 7002 6996 6996 6999 6998 6999
7012 7012 7010 7011 7012 7010 7009 6999 6998 7002 6999 6998 7000 6996 6996
7010 7010 7010 7000 7000 7006 7009 6999 6997 6996 7004 6997 6998 6999 6996
7010 7010 7010 7000 7000 7000 7009 7000 6994 6996 7002 6996 6996 6998 6999
7011 7011 7010 7010 7010 7010 7009 6999 6997 7002 6994 6997 6999 6998 6999
7011 7011 7010 7010 7000 7010 6997 6999 6994 7002 6999 6998 6998 6998 6999
7000 7000 7010 7010 7011 7010 7000 6999 6994 6994 6999 6998 6996 6999 6999
7011 7011 7011 7001 7010 7010 7009 6999 7000 6994 6999 6999 6997 6996 6999
7011 7011 7011 7010 7000 6999 7009 7000 6996 7002 6999 6996 6999 6998 6999
7010 7010 7010 7009 7000 6999 7000 6999 6994 7002 6999 6999 6999 6999 6999
7011 7011 7010 7009 7010 7010 7000 6999 6994 6996 6999 6996 6997 6999 6999
7010 7010 7010 7010 7001 6999 7000 6999 6996 6996 6999 6996 6998 6999 7001
6997 6997 7010 7009 7000 7000 6997 6999 6994 6996 6999 6998 6998 6999 6999
7011 7011 7010 7009 7012 7010 7009 6999 6996 7002 6999 6999 6998 6998 6999
7010 7010 7000 7009 7000 7000 7009 6999 6996 7002 6999 6998 6997 6999 6999
7010 7010 7010 7000 7000 7000 6997 6996 6994 7002 6999 6996 6996 6998 6999
7011 7011 7010 7010 7009 7010 6997 7000 6994 7002 6999 6996 6998 6999 6999
7011 7011 7010 7010 7000 6999 7000 7000 6994 7002 6999 6998 6998 6996 6999
6997 6997 7001 7001 7010 7008 7009 6998 6997 6996 6999 6999 6996 6996 6996
7009 7009 7011 7010 7001 7000 6997 6999 7000 6996 6999 6999 6997 6998 6999

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 6997 bytes 100%
1,000 6996 bytes -1 byte 100%
10,000 6995 bytes -1 byte 100%
100,000 6994 bytes -1 byte 4.06%
1,000,000 6994 bytes 4.06%
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
7039 bytes +45 bytes (+0.64%) +1 byte
7038 bytes +44 bytes (+0.63%)
7055 bytes +61 bytes (+0.87%) +17 bytes
7060 bytes +66 bytes (+0.94%) +22 bytes
7093 bytes +99 bytes (+1.42%) +55 bytes
7140 bytes +146 bytes (+2.09%) +102 bytes
7180 bytes +186 bytes (+2.66%) +142 bytes
7212 bytes +218 bytes (+3.12%) +174 bytes
7248 bytes +254 bytes (+3.63%) +210 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
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 5866 bytes -1128 bytes (-16.13%)
Brotli (Wikipedia) brotli brotli -q 11 6456 bytes -538 bytes (-7.69%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 6635 bytes -359 bytes (-5.13%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 6834 bytes -160 bytes (-2.29%)
ZSTD (Wikipedia) zstd zstd -19 7006 bytes +12 bytes (+0.17%)
LZMA2 (Wikipedia) xz xz -9 7008 bytes +14 bytes (+0.20%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 7211 bytes +217 bytes (+3.10%)

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 2017.
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