Choose a version:
53% The original file has 55244 bytes (53.9k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 29097 bytes (28.4k, 53%).

After GZIP compression these minified files vary in size:
Microsoft
  9934 bytes (9.7k)
CDN, direct link
Boot
  9154 bytes (8.9k)
CDN, direct link
MaxCDN
  9154 bytes (8.9k)
CDN, direct link
cdnjs
  7718 bytes (7.5k)
CDN, direct link
gzip -6 (default)
  7688 bytes (7.5k)
local copy
gzip -9
  7671 bytes (7.5k)
local copy
cdnhttps
  7665 bytes (7.5k)
CDN, direct link
jsdelivr
  7655 bytes (7.5k)
CDN, direct link
libdeflate -12
  7421 bytes (7.2k)
local copy
7zip -mx=9 -tgzip
  7410 bytes (7.2k)
local copy
kzip -s0 -rn -b1
  7406 bytes (7.2k)
local copy
pigz -11 -n
  7378 bytes (7.2k)
local copy
Zopfli
  7365 bytes (7.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.1.0.min.js

You will automatically get the smallest Bootstrap 3.1.0 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 290 bytes by using my Bootstrap 3.1.0 Zopfli version instead of the best available CDN (3.94% smaller than jsdelivr, 7365 vs. 7655 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 --mls2048 --bsr40 --lazy --ohh

(found November 23, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 2048  --mls2048
block splitting recursion 40  --bsr40
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/v3.1.0/dist/js/bootstrap.min.js --location | md5sum
e1d08589ec26bec3a81625ce274d76d9  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.1.0.min.zopfli.js.gz | md5sum
e1d08589ec26bec3a81625ce274d76d9  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.1.0/dist/js/bootstrap.min.js --location | sha1sum
c6a8a0f02ee0ecd975226ae4b38e9660750d1f93  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.1.0.min.zopfli.js.gz | sha1sum
c6a8a0f02ee0ecd975226ae4b38e9660750d1f93  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 9934 bytes e1d08589ec26bec3a81625ce274d76d9 (invalid)
Boot 9154 bytes e1d08589ec26bec3a81625ce274d76d9 (invalid)
MaxCDN 9154 bytes e1d08589ec26bec3a81625ce274d76d9 (invalid)
cdnjs 7718 bytes e1d08589ec26bec3a81625ce274d76d9 (invalid)
cdnhttps 7665 bytes e1d08589ec26bec3a81625ce274d76d9 December 24, 2015 @ 07:36
jsdelivr 7655 bytes e1d08589ec26bec3a81625ce274d76d9 (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
7365 bytes -1 byte zopfli --i100000 --mls2048 --bsr40 --lazy --ohh November 23, 2015 @ 15:34
7366 bytes -1 byte zopfli --i10000 --mls2048 --bsr14 --lazy --ohh September 10, 2015 @ 18:41
7367 bytes -1 byte zopfli --i1000 --mls2048 --bsr8 --lazy --ohh September 10, 2015 @ 16:50
7368 bytes -1 byte zopfli --i1000 --mls512 --bsr4 --lazy --ohh September 10, 2015 @ 16:50
7369 bytes zopfli --i100 --mls512 --bsr2 --lazy --ohh September 10, 2015 @ 16:29

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 @ 14:35.

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
7377 7377 7377 7378 7370 7368 7372 7368 7368 7374 7374 7373 7371 7369 7372
7368 7368 7372 7367 7367 7368 7368 7367 7368 7367 7374 7367 7367 7374 7374
7367 7367 7372 7367 7369 7368 7368 7368 7369 7370 7373 7368 7373 7374 7374
7376 7376 7368 7368 7368 7368 7368 7367 7368 7367 7368 7368 7368 7368 7373
7367 7367 7372 7367 7368 7368 7368 7368 7368 7370 7365 7368 7377 7368 7373
7376 7376 7372 7367 7368 7368 7368 7367 7368 7367 7367 7367 7378 7373 7374
7368 7368 7372 7367 7368 7368 7368 7367 7368 7370 7370 7369 7378 7368 7368
7368 7368 7376 7367 7370 7368 7368 7368 7368 7370 7367 7369 7368 7368 7368
7376 7376 7372 7367 7369 7368 7368 7368 7368 7370 7367 7368 7367 7367 7373
7367 7367 7375 7367 7369 7368 7368 7367 7368 7367 7365 7368 7374 7373 7373
7367 7367 7372 7367 7370 7367 7367 7369 7369 7367 7365 7368 7373 7374 7374
7376 7376 7373 7367 7368 7367 7368 7368 7367 7368 7367 7368 7368 7368 7373
7377 7377 7376 7369 7369 7368 7368 7367 7368 7368 7372 7367 7374 7368 7373
7376 7376 7372 7367 7368 7368 7368 7368 7369 7368 7367 7368 7367 7368 7367
7370 7370 7372 7367 7368 7368 7368 7367 7368 7370 7367 7368 7368 7368 7369
7367 7367 7372 7367 7369 7368 7368 7367 7368 7370 7365 7368 7368 7367 7374
7377 7377 7375 7367 7368 7368 7368 7367 7368 7369 7365 7367 7376 7374 7374
7367 7367 7372 7367 7368 7367 7368 7367 7368 7369 7367 7368 7376 7374 7373
7370 7370 7368 7367 7368 7367 7368 7368 7369 7367 7371 7368 7367 7368 7368
7376 7376 7372 7367 7368 7367 7368 7368 7369 7367 7367 7368 7373 7368 7373
7367 7367 7372 7367 7368 7368 7368 7368 7368 7367 7370 7368 7367 7368 7373
7370 7370 7372 7369 7369 7368 7368 7368 7368 7368 7365 7367 7369 7367 7365
7367 7367 7372 7367 7368 7367 7368 7367 7368 7370 7365 7373 7368 7368 7373

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 7368 bytes 100%
1,000 7367 bytes -1 byte 100%
10,000 7366 bytes -1 byte 100%
100,000 7365 bytes -1 byte 2.32%
1,000,000 7365 bytes 2.32%
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
7407 bytes +42 bytes (+0.57%) +1 byte
7406 bytes +41 bytes (+0.56%)
7420 bytes +55 bytes (+0.75%) +14 bytes
7425 bytes +60 bytes (+0.81%) +19 bytes
7466 bytes +101 bytes (+1.37%) +60 bytes
7511 bytes +146 bytes (+1.98%) +105 bytes
7545 bytes +180 bytes (+2.44%) +139 bytes
7579 bytes +214 bytes (+2.91%) +173 bytes
7616 bytes +251 bytes (+3.41%) +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 6167 bytes -1198 bytes (-16.27%)
Brotli (Wikipedia) brotli brotli -q 11 6806 bytes -559 bytes (-7.59%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 6920 bytes -445 bytes (-6.04%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 7193 bytes -172 bytes (-2.34%)
ZSTD (Wikipedia) zstd zstd -19 7379 bytes +14 bytes (+0.19%)
LZMA2 (Wikipedia) xz xz -9 7380 bytes +15 bytes (+0.20%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 7569 bytes +204 bytes (+2.77%)

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