Choose a version:
53% The original file has 55258 bytes (54.0k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 29110 bytes (28.4k, 53%).

After GZIP compression these minified files vary in size:
Microsoft
  9946 bytes (9.7k)
CDN, direct link
Boot
  9167 bytes (9.0k)
CDN, direct link
MaxCDN
  9167 bytes (9.0k)
CDN, direct link
Baidu
  7736 bytes (7.6k)
CDN, direct link
cdnjs
  7731 bytes (7.5k)
CDN, direct link
gzip -6 (default)
  7702 bytes (7.5k)
local copy
gzip -9
  7684 bytes (7.5k)
local copy
unpkg
  7681 bytes (7.5k)
CDN, direct link
cdnhttps
  7679 bytes (7.5k)
CDN, direct link
Yandex
  7668 bytes (7.5k)
CDN, direct link
jsdelivr
  7668 bytes (7.5k)
CDN, direct link
libdeflate -12
  7434 bytes (7.3k)
local copy
7zip -mx=9 -tgzip
  7423 bytes (7.2k)
local copy
kzip -s0 -rn -b1
  7419 bytes (7.2k)
local copy
pigz -11 -n
  7384 bytes (7.2k)
local copy
Zopfli
  7376 bytes (7.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.1.1.min.js

You will automatically get the smallest Bootstrap 3.1.1 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 292 bytes by using my Bootstrap 3.1.1 Zopfli version instead of the best available CDN (3.96% smaller than jsdelivr, 7376 vs. 7668 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 --i1000000 --mb8 --mls64 --bsr40 --lazy --ohh

(found February 26, 2016)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 64  --mls64
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/v3.1.1/dist/js/bootstrap.min.js --location | md5sum
ba847811448ef90d98d272aeccef2a95  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.1.1.min.zopfli.js.gz | md5sum
ba847811448ef90d98d272aeccef2a95  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.1.1/dist/js/bootstrap.min.js --location | sha1sum
5814e91bb6276f4de8b7951c965f2f190a03978d  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.1.1.min.zopfli.js.gz | sha1sum
5814e91bb6276f4de8b7951c965f2f190a03978d  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 9946 bytes ba847811448ef90d98d272aeccef2a95 (invalid)
Boot 9167 bytes ba847811448ef90d98d272aeccef2a95 (invalid)
MaxCDN 9167 bytes ba847811448ef90d98d272aeccef2a95 (invalid)
cdnjs 7731 bytes ba847811448ef90d98d272aeccef2a95 (invalid)
unpkg 7681 bytes ba847811448ef90d98d272aeccef2a95 July 11, 2016 @ 16:21
cdnhttps 7679 bytes ba847811448ef90d98d272aeccef2a95 December 24, 2015 @ 07:36
Yandex 7668 bytes ba847811448ef90d98d272aeccef2a95 (invalid)
jsdelivr 7668 bytes ba847811448ef90d98d272aeccef2a95 (invalid)

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 7736 bytes d1ea2970e53802116381cfd3f61a747a 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
7376 bytes -1 byte zopfli --i1000000 --mls64 --bsr40 --lazy --ohh February 26, 2016 @ 14:45
7377 bytes -1 byte zopfli --i100000 --mls2 --bsr10 --lazy --ohh November 18, 2015 @ 09:24
7378 bytes -1 byte zopfli --i1000 --mls2048 --bsr12 --lazy --ohh September 10, 2015 @ 16:49
7379 bytes -1 byte zopfli --i1000 --mls1024 --bsr6 --lazy --ohh September 10, 2015 @ 16:49
7380 bytes zopfli --i100 --mls512 --bsr2 --lazy --ohh September 10, 2015 @ 16:28

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 @ 16:21.

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, 100,000 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
7389 7389 7390 7390 7390 7380 7379 7384 7378 7384 7385 7384 7387 7385 7384
7387 7387 7384 7378 7381 7379 7379 7376 7380 7381 7380 7381 7383 7383 7384
7387 7387 7387 7379 7379 7380 7379 7379 7377 7379 7379 7380 7384 7384 7384
7387 7387 7383 7380 7380 7379 7379 7380 7377 7379 7379 7380 7378 7380 7383
7379 7379 7385 7376 7379 7379 7379 7380 7379 7379 7380 7377 7384 7383 7383
7379 7379 7383 7377 7379 7376 7379 7379 7377 7378 7379 7380 7383 7384 7384
7376 7376 7386 7377 7376 7379 7377 7381 7379 7379 7383 7377 7379 7379 7379
7387 7387 7384 7380 7381 7376 7379 7376 7377 7379 7381 7380 7380 7379 7384
7379 7379 7381 7379 7379 7378 7379 7376 7379 7379 7376 7377 7383 7379 7383
7387 7387 7384 7379 7379 7378 7379 7381 7379 7379 7378 7380 7384 7379 7384
7378 7378 7384 7379 7380 7379 7379 7380 7379 7380 7379 7381 7383 7379 7383
7379 7379 7385 7380 7379 7379 7379 7380 7379 7380 7379 7377 7380 7379 7383
7388 7388 7385 7379 7379 7379 7379 7379 7379 7380 7378 7381 7388 7383 7384
7388 7388 7385 7379 7384 7379 7380 7381 7379 7379 7379 7381 7380 7380 7379
7388 7388 7385 7379 7379 7379 7379 7381 7377 7380 7377 7379 7379 7378 7380
7379 7379 7384 7379 7379 7376 7379 7380 7380 7379 7379 7380 7383 7379 7383
7388 7388 7385 7376 7379 7376 7379 7380 7380 7380 7379 7381 7383 7384 7383
7378 7378 7385 7379 7379 7379 7379 7381 7377 7379 7380 7379 7384 7379 7384
7379 7379 7383 7378 7379 7379 7379 7380 7377 7380 7379 7379 7380 7380 7383
7386 7386 7384 7379 7379 7379 7379 7380 7377 7379 7379 7380 7380 7379 7379
7379 7379 7381 7379 7379 7376 7379 7381 7377 7379 7378 7377 7381 7383 7383
7379 7379 7384 7376 7379 7379 7379 7379 7379 7378 7380 7379 7383 7384 7384
7379 7379 7385 7379 7379 7376 7380 7380 7377 7379 7379 7379 7388 7383 7384

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 7379 bytes 100%
1,000 7378 bytes -1 byte 100%
10,000 7378 bytes 100%
100,000 7377 bytes -1 byte 14.78%
1,000,000 7376 bytes -1 byte 10.14%
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
7419 bytes +43 bytes (+0.58%)
7419 bytes +43 bytes (+0.58%)
7431 bytes +55 bytes (+0.75%) +12 bytes
7436 bytes +60 bytes (+0.81%) +17 bytes
7479 bytes +103 bytes (+1.40%) +60 bytes
7524 bytes +148 bytes (+2.01%) +105 bytes
7556 bytes +180 bytes (+2.44%) +137 bytes
7592 bytes +216 bytes (+2.93%) +173 bytes
7628 bytes +252 bytes (+3.42%) +209 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 6183 bytes -1193 bytes (-16.17%)
Brotli (Wikipedia) brotli brotli -q 11 6815 bytes -561 bytes (-7.61%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 6930 bytes -446 bytes (-6.05%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 7204 bytes -172 bytes (-2.33%)
LZMA2 (Wikipedia) xz xz -9 7388 bytes +12 bytes (+0.16%)
ZSTD (Wikipedia) zstd zstd -19 7393 bytes +17 bytes (+0.23%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 7583 bytes +207 bytes (+2.81%)

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