Bootstrap 3.1.0 - as small as it gets (near-perfect GZIP compression)

Choose a version:

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
Boot	9154 bytes (8.9k)	CDN
MaxCDN	9154 bytes (8.9k)	CDN
cdnjs	7718 bytes (7.5k)	CDN
gzip -6 (default)	7688 bytes (7.5k)	local copy
gzip -9	7671 bytes (7.5k)	local copy
jsdelivr	7655 bytes (7.5k)	CDN
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
zultra	7400 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 (or via HTTPS)

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):

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 --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 https://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 https://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)
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:

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
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 July 20, 2020 @ 12:49.

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
2	7377	7377	7377	7378	7370	7368	7372	7368	7368	7374	7374	7373	7371	7369	7372
4	7368	7368	7372	7367	7367	7368	7368	7367	7368	7367	7374	7367	7367	7374	7374
6	7367	7367	7372	7367	7369	7368	7368	7368	7369	7370	7373	7368	7373	7374	7374
7	7376	7376	7368	7368	7368	7368	7368	7367	7368	7367	7368	7368	7368	7368	7373
8	7367	7367	7372	7367	7368	7368	7368	7368	7368	7370	7365	7368	7377	7368	7373
9	7376	7376	7372	7367	7368	7368	7368	7367	7368	7367	7367	7367	7378	7373	7374
10	7368	7368	7372	7367	7368	7368	7368	7367	7368	7370	7370	7369	7378	7368	7368
11	7368	7368	7376	7367	7370	7368	7368	7368	7368	7370	7367	7369	7368	7368	7368
12	7376	7376	7372	7367	7369	7368	7368	7368	7368	7370	7367	7368	7367	7367	7373
13	7367	7367	7375	7367	7369	7368	7368	7367	7368	7367	7365	7368	7374	7373	7373
14	7367	7367	7372	7367	7370	7367	7367	7369	7369	7367	7365	7368	7373	7374	7374
15	7376	7376	7373	7367	7368	7367	7368	7368	7367	7368	7367	7368	7368	7368	7373
16	7377	7377	7376	7369	7369	7368	7368	7367	7368	7368	7372	7367	7374	7368	7373
17	7376	7376	7372	7367	7368	7368	7368	7368	7369	7368	7367	7368	7367	7368	7367
18	7370	7370	7372	7367	7368	7368	7368	7367	7368	7370	7367	7368	7368	7368	7369
19	7367	7367	7372	7367	7369	7368	7368	7367	7368	7370	7365	7368	7368	7367	7374
20	7377	7377	7375	7367	7368	7368	7368	7367	7368	7369	7365	7367	7376	7374	7374
21	7367	7367	7372	7367	7368	7367	7368	7367	7368	7369	7367	7368	7376	7374	7373
22	7370	7370	7368	7367	7368	7367	7368	7368	7369	7367	7371	7368	7367	7368	7368
23	7376	7376	7372	7367	7368	7367	7368	7368	7369	7367	7367	7368	7373	7368	7373
25	7367	7367	7372	7367	7368	7368	7368	7368	7368	7367	7370	7368	7367	7368	7373
30	7370	7370	7372	7369	7369	7368	7368	7368	7368	7368	7365	7367	7369	7367	7365
40	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
(any)	7407 bytes	+42 bytes (+0.57%)	+1 byte
1	7406 bytes	+41 bytes (+0.56%)	–
2	7420 bytes	+55 bytes (+0.75%)	+14 bytes
3	7425 bytes	+60 bytes (+0.81%)	+19 bytes
4	7466 bytes	+101 bytes (+1.37%)	+60 bytes
5	7511 bytes	+146 bytes (+1.98%)	+105 bytes
6	7545 bytes	+180 bytes (+2.44%)	+139 bytes
7	7579 bytes	+214 bytes (+2.91%)	+173 bytes
8	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.
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	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%)
Zstandard (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):

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 2026.
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.