Choose a version:
53% The original file has 66732 bytes (65.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 35452 bytes (34.6k, 53%).

After GZIP compression these minified files vary in size:
Microsoft
  12247 bytes (12.0k)
CDN, direct link
Boot
  11290 bytes (11.0k)
CDN, direct link
MaxCDN
  11290 bytes (11.0k)
CDN, direct link
cdnjs
  9490 bytes (9.3k)
CDN, direct link
gzip -6 (default)
  9430 bytes (9.2k)
local copy
cdnhttps
  9407 bytes (9.2k)
CDN, direct link
gzip -9
  9399 bytes (9.2k)
local copy
unpkg
  9392 bytes (9.2k)
CDN, direct link
jsdelivr
  9379 bytes (9.2k)
CDN, direct link
kzip -s0 -rn -b1
  9088 bytes (8.9k)
local copy
7zip -mx=9 -tgzip
  9087 bytes (8.9k)
local copy
libdeflate -12
  9087 bytes (8.9k)
local copy
pigz -11 -n
  9035 bytes (8.8k)
local copy
Zopfli
  9025 bytes (8.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.2.min.js

You will automatically get the smallest Bootstrap 3.3.2 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 354 bytes by using my Bootstrap 3.3.2 Zopfli version instead of the best available CDN (3.92% smaller than jsdelivr, 9025 vs. 9379 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 --mls256 --bsr25 --lazy --ohh

(found February 26, 2016)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 256  --mls256
block splitting recursion 25  --bsr25
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/v3.3.2/dist/js/bootstrap.min.js --location | md5sum
046ba2b5f4cff7d2eaaa1af55caa9fd8  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.2.min.zopfli.js.gz | md5sum
046ba2b5f4cff7d2eaaa1af55caa9fd8  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.3.2/dist/js/bootstrap.min.js --location | sha1sum
b3f2ef9f985e7906c9360756b73cd64bf7733647  -
curl --silent --compressed http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.2.min.zopfli.js.gz | sha1sum
b3f2ef9f985e7906c9360756b73cd64bf7733647  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 12247 bytes 046ba2b5f4cff7d2eaaa1af55caa9fd8 (invalid)
Boot 11290 bytes 046ba2b5f4cff7d2eaaa1af55caa9fd8 (invalid)
MaxCDN 11290 bytes 046ba2b5f4cff7d2eaaa1af55caa9fd8 (invalid)
cdnjs 9490 bytes 046ba2b5f4cff7d2eaaa1af55caa9fd8 (invalid)
cdnhttps 9407 bytes 046ba2b5f4cff7d2eaaa1af55caa9fd8 December 24, 2015 @ 07:36
unpkg 9392 bytes 046ba2b5f4cff7d2eaaa1af55caa9fd8 July 11, 2016 @ 16:21
jsdelivr 9379 bytes 046ba2b5f4cff7d2eaaa1af55caa9fd8 (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
9025 bytes -1 byte zopfli --i1000000 --mls256 --bsr25 --lazy --ohh February 26, 2016 @ 16:36
9026 bytes -1 byte zopfli --i10000 --mls256 --bsr8 --lazy --ohh September 17, 2015 @ 22:10
9027 bytes -1 byte zopfli --i10000 --mls512 --bsr4 --lazy --ohh September 10, 2015 @ 17:29
9028 bytes -1 byte zopfli --i10000 --mls512 --bsr6 --lazy --ohh September 10, 2015 @ 17:24
9029 bytes -1 byte zopfli --i1000 --mls512 --bsr13 --lazy --ohh September 10, 2015 @ 16:35
9030 bytes zopfli --i100 --mls1024 --bsr6 --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 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 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
9037 9037 9037 9037 9038 9038 9039 9038 9037 9039 9040 9039 9037 9030 9038
9027 9027 9027 9028 9029 9031 9029 9027 9027 9029 9029 9037 9035 9029 9036
9028 9028 9029 9028 9031 9031 9027 9027 9028 9028 9031 9028 9029 9027 9029
9027 9027 9027 9028 9029 9029 9029 9028 9029 9029 9031 9031 9029 9029 9030
9025 9025 9028 9028 9029 9029 9028 9025 9030 9029 9031 9031 9029 9032 9029
9028 9028 9028 9029 9028 9029 9029 9030 9029 9030 9032 9032 9030 9029 9029
9025 9025 9028 9031 9029 9029 9029 9029 9030 9029 9033 9028 9029 9028 9030
9025 9025 9028 9031 9030 9031 9030 9025 9029 9029 9031 9031 9029 9029 9030
9028 9028 9031 9028 9031 9029 9029 9028 9029 9029 9029 9031 9029 9027 9030
9028 9028 9028 9028 9029 9029 9029 9025 9029 9029 9029 9028 9029 9036 9031
9028 9028 9029 9031 9030 9029 9029 9029 9029 9029 9031 9029 9029 9028 9030
9029 9029 9028 9027 9029 9029 9029 9028 9029 9029 9029 9036 9029 9029 9030
9028 9028 9028 9027 9029 9029 9030 9029 9029 9029 9031 9030 9029 9029 9030
9027 9027 9028 9031 9029 9029 9029 9025 9029 9030 9031 9030 9029 9028 9030
9028 9028 9029 9031 9029 9029 9029 9028 9027 9030 9031 9028 9029 9027 9028
9025 9025 9027 9028 9029 9029 9029 9028 9027 9030 9031 9029 9029 9029 9029
9025 9025 9029 9028 9029 9029 9029 9025 9027 9029 9031 9029 9029 9029 9029
9025 9025 9028 9028 9029 9029 9029 9025 9029 9029 9031 9028 9029 9029 9029
9025 9025 9029 9028 9029 9029 9029 9028 9029 9029 9029 9031 9029 9030 9030
9028 9028 9027 9028 9029 9029 9028 9028 9029 9029 9029 9031 9029 9027 9029
9028 9028 9028 9028 9029 9029 9029 9025 9029 9029 9033 9031 9030 9027 9029
9027 9027 9028 9027 9028 9030 9030 9028 9029 9029 9031 9029 9029 9028 9029
9028 9028 9029 9031 9029 9029 9029 9029 9029 9029 9029 9029 9029 9028 9029

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 9030 bytes 100%
1,000 9028 bytes -2 bytes 100%
10,000 9026 bytes -2 bytes 100%
100,000 9026 bytes 6.09%
1,000,000 9025 bytes -1 byte 6.09%
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
9089 bytes +64 bytes (+0.71%) +1 byte
9088 bytes +63 bytes (+0.70%)
9091 bytes +66 bytes (+0.73%) +3 bytes
9093 bytes +68 bytes (+0.75%) +5 bytes
9125 bytes +100 bytes (+1.11%) +37 bytes
9166 bytes +141 bytes (+1.56%) +78 bytes
9209 bytes +184 bytes (+2.04%) +121 bytes
9241 bytes +216 bytes (+2.39%) +153 bytes
9283 bytes +258 bytes (+2.86%) +195 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 7511 bytes -1514 bytes (-16.78%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 8211 bytes -814 bytes (-9.02%)
Brotli (Wikipedia) brotli brotli -q 11 8320 bytes -705 bytes (-7.81%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 8551 bytes -474 bytes (-5.25%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 8751 bytes -274 bytes (-3.04%)
LZMA2 (Wikipedia) xz xz -9 8996 bytes -29 bytes (-0.32%)
ZSTD (Wikipedia) zstd zstd -19 9042 bytes +17 bytes (+0.19%)

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