Bootstrap 3.4.0 - as small as it gets (near-perfect GZIP compression)

Choose a version:

The original file has 70815 bytes (69.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 37608 bytes (36.7k, 53%).

After GZIP compression these minified files vary in size:

cdnjs	10098 bytes (9.9k)	CDN
gzip -6 (default)	10058 bytes (9.8k)	local copy
Microsoft	10041 bytes (9.8k)	CDN
MaxCDN	10035 bytes (9.8k)	CDN
jsdelivr	10035 bytes (9.8k)	CDN
gzip -9	10019 bytes (9.8k)	local copy
unpkg	10006 bytes (9.8k)	CDN
libdeflate -12	9692 bytes (9.5k)	local copy
7zip -mx=9 -tgzip	9690 bytes (9.5k)	local copy
kzip -s0 -rn -b2	9690 bytes (9.5k)	local copy
zultra	9666 bytes (9.4k)	local copy
pigz -11 -n	9644 bytes (9.4k)	local copy
Zopfli	9632 bytes (9.4k)	local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.4.0.min.js (or via HTTPS)

You will automatically get the smallest Bootstrap 3.4.0 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 374 bytes by using my Bootstrap 3.4.0 Zopfli version instead of the best available CDN (3.88% smaller than unpkg, 9632 vs. 10006 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 --mls8192 --bsr11 --lazy --ohh

(found December 14, 2018)

Description	Value	Parameter
iterations	1000000	--i1000000
maximum blocks	8	--mb8
maximum length score	8192	--mls8192
block splitting recursion	11	--bsr11
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/v3.4.0/dist/js/bootstrap.min.js --location | md5sum
3d8308804264c5b751f6e54734c46897 -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.4.0.min.zopfli.js.gz | md5sum
3d8308804264c5b751f6e54734c46897 -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.4.0/dist/js/bootstrap.min.js --location | sha1sum
369a832ef7f8a57e9b59b84b181fdb4fc9125050 -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.4.0.min.zopfli.js.gz | sha1sum
369a832ef7f8a57e9b59b84b181fdb4fc9125050 -

All listed CDNs deliver identical contents:

CDN	Size (compressed)	MD5 (uncompressed)	Timestamp
cdnjs	10098 bytes	3d8308804264c5b751f6e54734c46897	(invalid)
Microsoft	10041 bytes	3d8308804264c5b751f6e54734c46897	January 15, 2019 @ 18:51
MaxCDN	10035 bytes	3d8308804264c5b751f6e54734c46897	(invalid)
jsdelivr	10035 bytes	3d8308804264c5b751f6e54734c46897	December 5, 2019 @ 13:18
unpkg	10006 bytes	3d8308804264c5b751f6e54734c46897	(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
9632 bytes	-1 byte	zopfli --i1000000 --mls8192 --bsr11 --lazy --ohh	December 14, 2018 @ 18:17
9633 bytes	-1 byte	zopfli --i10000 --mls8192 --bsr11 --lazy --ohh	December 14, 2018 @ 14:20
9634 bytes	-1 byte	zopfli --i10000 --mls256 --bsr20 --lazy --ohh	December 14, 2018 @ 14:18
9635 bytes	–	zopfli --i100 --mls256 --bsr20 --lazy --ohh	December 14, 2018 @ 13:57

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 @ 12:53.

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	9644	9644	9644	9643	9643	9643	9638	9636	9638	9635	9634	9635	9641	9646	9644
4	9636	9636	9634	9637	9636	9635	9636	9634	9636	9636	9635	9637	9636	9637	9637
6	9638	9638	9638	9637	9636	9637	9635	9634	9635	9636	9636	9636	9635	9635	9635
7	9636	9636	9641	9642	9642	9637	9636	9634	9635	9636	9636	9637	9637	9636	9637
8	9636	9636	9634	9641	9637	9641	9636	9634	9635	9636	9636	9637	9636	9643	9636
9	9635	9634	9636	9637	9637	9635	9636	9634	9635	9635	9636	9638	9645	9635	9636
10	9636	9636	9637	9642	9635	9641	9641	9636	9636	9636	9634	9637	9637	9635	9636
11	9636	9636	9634	9642	9635	9636	9636	9634	9634	9636	9635	9637	9632	9637	9637
12	9636	9636	9634	9637	9637	9634	9636	9634	9636	9636	9636	9635	9636	9637	9637
13	9636	9636	9634	9637	9637	9636	9636	9634	9635	9636	9636	9637	9636	9637	9636
14	9636	9636	9634	9637	9636	9636	9636	9634	9637	9635	9637	9637	9637	9643	9636
15	9637	9637	9635	9636	9635	9636	9636	9637	9635	9636	9636	9635	9636	9636	9632
16	9636	9636	9634	9642	9635	9636	9636	9635	9635	9635	9637	9635	9636	9636	9635
17	9636	9636	9634	9637	9634	9632	9635	9635	9635	9636	9635	9635	9636	9637	9636
18	9636	9636	9634	9636	9642	9636	9636	9636	9636	9636	9636	9637	9636	9635	9636
19	9636	9636	9635	9641	9634	9636	9637	9634	9636	9636	9635	9637	9636	9643	9636
20	9636	9636	9636	9637	9635	9636	9635	9634	9637	9636	9635	9638	9636	9637	9635
21	9636	9636	9634	9637	9635	9635	9636	9636	9637	9636	9635	9638	9636	9637	9636
22	9636	9636	9634	9637	9635	9635	9636	9634	9637	9636	9635	9637	9636	9643	9632
23	9636	9636	9636	9641	9635	9634	9637	9636	9635	9636	9634	9637	9637	9637	9636
25	9636	9636	9634	9637	9635	9636	9636	9635	9637	9636	9634	9635	9636	9643	9635
30	9636	9636	9634	9636	9635	9636	9634	9634	9635	9636	9637	9637	9636	9641	9638
40	9637	9637	9634	9637	9635	9636	9636	9636	9637	9634	9635	9637	9640	9637	9636

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	9635 bytes	–	100%
1,000	9635 bytes	–	100%
10,000	9633 bytes	-2 bytes	100%
100,000	9633 bytes	–	1.16%
1,000,000	9632 bytes	-1 byte	1.16%
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)	9690 bytes	+58 bytes (+0.60%)	–
1	9692 bytes	+60 bytes (+0.62%)	+2 bytes
2	9690 bytes	+58 bytes (+0.60%)	–
3	9715 bytes	+83 bytes (+0.86%)	+25 bytes
4	9723 bytes	+91 bytes (+0.94%)	+33 bytes
5	9763 bytes	+131 bytes (+1.36%)	+73 bytes
6	9802 bytes	+170 bytes (+1.76%)	+112 bytes
7	9833 bytes	+201 bytes (+2.09%)	+143 bytes
8	9877 bytes	+245 bytes (+2.54%)	+187 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	8105 bytes	-1527 bytes (-15.85%)
ZPAQ (Wikipedia)	zpaq	zpaq -method 69	8763 bytes	-869 bytes (-9.02%)
Brotli (Wikipedia)	brotli	brotli -q 11	8884 bytes	-748 bytes (-7.77%)
PPMd (Wikipedia)	7zip	7za a -mx=9 -m0=ppmd	9175 bytes	-457 bytes (-4.74%)
Burrows-Wheeler transform (Wikipedia)	bzip2	bzip2 -9	9473 bytes	-159 bytes (-1.65%)
LZMA2 (Wikipedia)	xz	xz -9	9568 bytes	-64 bytes (-0.66%)
Zstandard (Wikipedia)	zstd	zstd -19	9582 bytes	-50 bytes (-0.52%)

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.