Choose a version:
53% The original file has 69707 bytes (68.1k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 37045 bytes (36.2k, 53%).

After GZIP compression these minified files vary in size:
Microsoft
  13045 bytes (12.7k)
 CDN
Boot
  11889 bytes (11.6k)
 CDN
MaxCDN
  11889 bytes (11.6k)
 CDN
cdnjs
  9925 bytes (9.7k)
 CDN
gzip -6 (default)
  9855 bytes (9.6k)
 local copy
Sina
  9833 bytes (9.6k)
 CDN
unpkg
  9833 bytes (9.6k)
 CDN
gzip -9
  9829 bytes (9.6k)
 local copy
jsdelivr
  9810 bytes (9.6k)
 CDN
7zip -mx=9 -tgzip
  9524 bytes (9.3k)
 local copy
kzip -s0 -rn -b1
  9524 bytes (9.3k)
 local copy
libdeflate -12
  9515 bytes (9.3k)
 local copy
zultra
  9484 bytes (9.3k)
 local copy
pigz -11 -n
  9472 bytes (9.3k)
 local copy
Zopfli
  9463 bytes (9.2k)
 local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.7.min.js (or via HTTPS)

You will automatically get the smallest Bootstrap 3.3.7 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 347 bytes by using my Bootstrap 3.3.7 Zopfli version instead of the best available CDN (3.67% smaller than jsdelivr, 9463 vs. 9810 bytes):
Download
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 --mls128 --bsr8 --lazy --ohh

(found July 26, 2016)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 128  --mls128
block splitting recursion 8  --bsr8
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/v3.3.7/dist/js/bootstrap.min.js --location | md5sum
5869c96cc8f19086aee625d670d741f9  -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.7.min.zopfli.js.gz | md5sum
5869c96cc8f19086aee625d670d741f9  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.3.7/dist/js/bootstrap.min.js --location | sha1sum
430a443d74830fe9be26efca431f448c1b3740f9  -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.7.min.zopfli.js.gz | sha1sum
430a443d74830fe9be26efca431f448c1b3740f9  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 13045 bytes 5869c96cc8f19086aee625d670d741f9 September 19, 2016 @ 19:05
Boot 11889 bytes 5869c96cc8f19086aee625d670d741f9 July 26, 2016 @ 05:31
MaxCDN 11889 bytes 5869c96cc8f19086aee625d670d741f9 (invalid)
cdnjs 9925 bytes 5869c96cc8f19086aee625d670d741f9 July 26, 2016 @ 09:16
Sina 9833 bytes 5869c96cc8f19086aee625d670d741f9 May 17, 2018 @ 09:16
unpkg 9833 bytes 5869c96cc8f19086aee625d670d741f9 July 25, 2016 @ 21:54
jsdelivr 9810 bytes 5869c96cc8f19086aee625d670d741f9 (invalid)

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

Other Versions

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

5.2.3, 5.2.2, 5.2.1, 5.2.0,
5.1.3, 5.1.2, 5.1.1, 5.1.0,
5.0.2, 5.0.1, 5.0.0,
4.6.0,
4.5.3, 4.5.2, 4.5.1, 4.5.0,
4.4.1, 4.4.0,
4.3.1, 4.3.0,
4.2.1, 4.2.0,
4.1.3, 4.1.2, 4.1.1, 4.1.0, 4.0.0,
3.4.1, 3.4.0,
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
9463 bytes -1 byte zopfli --i1000000 --mls128 --bsr8 --lazy --ohh July 26, 2016 @ 18:15
9464 bytes -1 byte zopfli --i10000 --mls4096 --bsr40 --lazy --ohh July 25, 2016 @ 22:12
9465 bytes -1 byte zopfli --i1000 --mls4096 --bsr40 --lazy --ohh July 25, 2016 @ 22:07
9466 bytes – zopfli --i100 --mls128 --bsr17 --lazy --ohh July 25, 2016 @ 21:58

If there are multiple parameter sets yielding the same compressed size, only the first one found is shown.

Most recent activity on July 20, 2020 @ 12:52.

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, 1,000,000 or 10,000,000.
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
2 9474 9474 9474 9474 9475 9475 9474 9474 9475 9479 9479 9467 9473 9473 9474
4 9467 9467 9466 9467 9465 9467 9465 9468 9466 9467 9467 9465 9467 9466 9477
6 9465 9465 9469 9468 9468 9466 9467 9468 9465 9466 9466 9465 9466 9467 9467
7 9465 9465 9467 9466 9466 9466 9465 9468 9465 9465 9467 9466 9471 9466 9469
8 9465 9465 9465 9466 9466 9466 9463 9468 9465 9465 9466 9465 9465 9466 9466
9 9465 9465 9466 9466 9466 9466 9466 9467 9467 9465 9465 9465 9467 9467 9467
10 9465 9465 9469 9466 9465 9466 9466 9467 9466 9466 9464 9466 9467 9466 9466
11 9465 9465 9467 9465 9465 9465 9465 9467 9465 9465 9467 9465 9471 9466 9466
12 9465 9465 9468 9468 9466 9465 9466 9467 9465 9466 9465 9465 9467 9466 9465
13 9465 9465 9466 9466 9466 9466 9467 9467 9465 9465 9467 9465 9467 9466 9465
14 9465 9465 9469 9468 9465 9466 9465 9466 9467 9465 9467 9465 9468 9466 9466
15 9465 9465 9465 9466 9466 9466 9465 9467 9465 9465 9465 9466 9471 9492 9465
16 9465 9465 9468 9466 9465 9466 9465 9467 9465 9467 9464 9467 9467 9465 9466
17 9465 9465 9465 9466 9466 9466 9465 9466 9465 9467 9465 9465 9467 9466 9466
18 9465 9465 9466 9466 9465 9465 9466 9468 9465 9467 9466 9465 9467 9466 9469
19 9465 9465 9465 9468 9465 9466 9465 9466 9465 9465 9464 9465 9467 9466 9465
20 9465 9465 9469 9466 9465 9465 9466 9468 9465 9468 9464 9466 9467 9466 9465
21 9467 9467 9466 9465 9466 9465 9466 9467 9465 9465 9466 9465 9467 9466 9466
22 9465 9465 9466 9466 9465 9465 9465 9467 9465 9465 9467 9465 9469 9466 9466
23 9465 9465 9469 9466 9466 9466 9465 9468 9465 9465 9466 9465 9467 9466 9466
25 9466 9466 9466 9466 9466 9466 9466 9467 9465 9465 9466 9465 9467 9466 9465
30 9465 9465 9466 9466 9465 9465 9466 9468 9466 9464 9467 9465 9477 9468 9464
40 9466 9466 9466 9466 9465 9465 9465 9467 9465 9465 9467 9464 9467 9465 9466

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 9466 bytes – 100%
1,000 9465 bytes -1 byte 100%
10,000 9464 bytes -1 byte 100%
100,000 9464 bytes – 2.32%
1,000,000 9463 bytes -1 byte 2.32%
10,000,000 9463 bytes – 0.29%

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
(any) 9525 bytes +62 bytes (+0.66%) +1 byte
1 9524 bytes +61 bytes (+0.64%) –
2 9528 bytes +65 bytes (+0.69%) +4 bytes
3 9546 bytes +83 bytes (+0.88%) +22 bytes
4 9555 bytes +92 bytes (+0.97%) +31 bytes
5 9599 bytes +136 bytes (+1.44%) +75 bytes
6 9645 bytes +182 bytes (+1.92%) +121 bytes
7 9676 bytes +213 bytes (+2.25%) +152 bytes
8 9720 bytes +257 bytes (+2.72%) +196 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 - for example, your browser actually supports it !
Algorithm Program Parameters Size Compared To Best Zopfli
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 7889 bytes -1574 bytes (-16.63%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 8548 bytes -915 bytes (-9.67%)
Brotli (Wikipedia) brotli brotli -q 11 8710 bytes -753 bytes (-7.96%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 8936 bytes -527 bytes (-5.57%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 9194 bytes -269 bytes (-2.84%)
LZMA2 (Wikipedia) xz xz -9 9412 bytes -51 bytes (-0.54%)
Zstandard (Wikipedia) zstd zstd -19 9469 bytes +6 bytes (+0.06%)

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):
Load and Parse Data


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 2025.
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

All trademarks are property of their respective owners. You know, the boring legal stuff.