BackboneJS 1.2.1 - as small as it gets (near-perfect GZIP compression)

The original file has 70852 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 22857 bytes (22.3k, 32%).

After GZIP compression these minified files vary in size:

Boot	8671 bytes (8.5k)	CDN
cdnjs	7466 bytes (7.3k)	CDN
gzip -6 (default)	7441 bytes (7.3k)	local copy
gzip -9	7432 bytes (7.3k)	local copy
unpkg	7429 bytes (7.3k)	CDN
jsdelivr	7414 bytes (7.2k)	CDN
7zip -mx=9 -tgzip	7221 bytes (7.1k)	local copy
zultra	7216 bytes (7.0k)	local copy
libdeflate -12	7210 bytes (7.0k)	local copy
pigz -11 -n	7206 bytes (7.0k)	local copy
kzip -s0 -rn -b0	7202 bytes (7.0k)	local copy
Zopfli	7200 bytes (7.0k)	local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-1.2.1.min.js (or via HTTPS)

You will automatically get the smallest BackboneJS 1.2.1 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 214 bytes by using my BackboneJS 1.2.1 Zopfli version instead of the best available CDN (2.97% smaller than jsdelivr, 7200 vs. 7414 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 --i10000 --mb8 --mls2048 --bsr13 --lazy --ohh

(found September 8, 2015)

Description	Value	Parameter
iterations	10000	--i10000
maximum blocks	8	--mb8
maximum length score	2048	--mls2048
block splitting recursion	13	--bsr13
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/jashkenas/backbone/1.2.1/backbone-min.js --location | md5sum
1671918bffa92a85d3caaf2a2bd24e7a -
curl --silent --compressed https://minime.stephan-brumme.com/files/backbonejs/backbone-1.2.1.min.zopfli.js.gz | md5sum
1671918bffa92a85d3caaf2a2bd24e7a -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/1.2.1/backbone-min.js --location | sha1sum
f745a8455c6355a24decf31b6c6c2c1dd42f0466 -
curl --silent --compressed https://minime.stephan-brumme.com/files/backbonejs/backbone-1.2.1.min.zopfli.js.gz | sha1sum
f745a8455c6355a24decf31b6c6c2c1dd42f0466 -

All listed CDNs deliver identical contents:

CDN	Size (compressed)	MD5 (uncompressed)	Timestamp
Boot	8671 bytes	1671918bffa92a85d3caaf2a2bd24e7a	(invalid)
cdnjs	7466 bytes	1671918bffa92a85d3caaf2a2bd24e7a	(invalid)
unpkg	7429 bytes	1671918bffa92a85d3caaf2a2bd24e7a	July 11, 2016 @ 16:18
jsdelivr	7414 bytes	1671918bffa92a85d3caaf2a2bd24e7a	(invalid)

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

Other Versions

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

1.4.1, 1.4.0,
1.3.3, 1.3.2, 1.3.1, 1.3.0,
1.2.3, 1.2.2, 1.2.1, 1.2.0,
1.1.2, 1.1.1, 1.1.0,
1.0.0,
0.9.10, 0.9.9, 0.9.2, 0.9.1, 0.9.0,
0.3.3, 0.3.2, 0.3.1, 0.3.0,
0.2.0,
0.1.2, 0.1.1

The project site contains an overview how well these versions were compressed.
Other interesting projects are AngularJS, Bootstrap, D3, Dojo, Ember, jQuery, Knockout, lodash, React, Socket.IO, ThreeJS, UnderscoreJS and Vue.

Changelog

Best Zopfli parameters so far:

Size	Improvement	Parameters	Found
7200 bytes	-1 byte	zopfli --i10000 --mls2048 --bsr13 --lazy --ohh	September 8, 2015 @ 12:24
7201 bytes	-1 byte	zopfli --i1000 --mls512 --bsr9 --lazy --ohh	September 8, 2015 @ 11:39
7202 bytes	–	zopfli --i100 --mls512 --bsr14 --lazy --ohh	September 8, 2015 @ 11:32

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, 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
2	7204	7203	7203	7203	7203	7204	7204	7204	7202	7204	7204	7202	7201	7202	7201
4	7202	7202	7201	7202	7202	7203	7202	7202	7202	7203	7201	7203	7203	7203	7203
6	7203	7202	7203	7210	7201	7210	7204	7210	7203	7201	7204	7203	7202	7202	7201
7	7210	7201	7211	7212	7205	7203	7204	7209	7202	7207	7202	7204	7202	7203	7203
8	7203	7204	7202	7202	7201	7203	7204	7201	7201	7203	7201	7204	7202	7203	7203
9	7211	7202	7202	7202	7202	7211	7202	7210	7200	7201	7201	7203	7203	7203	7203
10	7203	7202	7202	7200	7201	7202	7203	7211	7201	7201	7201	7204	7202	7203	7201
11	7203	7203	7203	7200	7201	7203	7203	7204	7200	7201	7201	7204	7203	7203	7203
12	7202	7202	7211	7201	7202	7203	7202	7201	7200	7200	7201	7203	7202	7203	7203
13	7202	7202	7202	7202	7201	7203	7202	7201	7201	7200	7200	7204	7202	7203	7203
14	7202	7202	7203	7200	7201	7202	7202	7201	7201	7200	7201	7203	7203	7203	7203
15	7202	7202	7212	7210	7202	7203	7203	7201	7201	7202	7202	7205	7202	7203	7203
16	7210	7202	7203	7201	7202	7202	7202	7201	7204	7201	7201	7204	7202	7203	7203
17	7202	7202	7202	7201	7203	7203	7203	7201	7201	7202	7202	7205	7202	7203	7203
18	7202	7202	7203	7201	7202	7201	7202	7201	7202	7202	7201	7205	7203	7203	7203
19	7202	7202	7202	7201	7202	7201	7210	7210	7201	7202	7201	7204	7203	7203	7203
20	7202	7202	7202	7202	7201	7201	7202	7201	7201	7203	7201	7204	7203	7203	7203
21	7202	7202	7202	7202	7201	7202	7203	7201	7202	7206	7200	7207	7203	7203	7203
22	7201	7210	7211	7210	7201	7203	7210	7211	7201	7201	7202	7205	7203	7203	7203
23	7200	7203	7202	7201	7201	7203	7203	7201	7201	7201	7200	7204	7203	7203	7203
25	7202	7202	7211	7201	7202	7203	7203	7211	7201	7201	7200	7204	7203	7203	7203
30	7203	7201	7200	7202	7202	7203	7202	7202	7201	7201	7202	7205	7203	7203	7203
40	7202	7203	7203	7201	7201	7202	7203	7201	7201	7202	7202	7205	7202	7203	7203

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	7202 bytes	–	100%
1,000	7201 bytes	-1 byte	100%
10,000	7200 bytes	-1 byte	100%
100,000	7200 bytes	–	18.55%
1,000,000	7200 bytes	–	0.29%
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)	7202 bytes	+2 bytes (+0.03%)	–
1	7202 bytes	+2 bytes (+0.03%)	–
2	7232 bytes	+32 bytes (+0.44%)	+30 bytes
3	7261 bytes	+61 bytes (+0.85%)	+59 bytes
4	7300 bytes	+100 bytes (+1.39%)	+98 bytes
5	7314 bytes	+114 bytes (+1.58%)	+112 bytes
6	7330 bytes	+130 bytes (+1.81%)	+128 bytes
7	7361 bytes	+161 bytes (+2.24%)	+159 bytes
8	7389 bytes	+189 bytes (+2.63%)	+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	6275 bytes	-925 bytes (-12.85%)
PPMd (Wikipedia)	7zip	7za a -mx=9 -m0=ppmd	6738 bytes	-462 bytes (-6.42%)
Brotli (Wikipedia)	brotli	brotli -q 11	6743 bytes	-457 bytes (-6.35%)
ZPAQ (Wikipedia)	zpaq	zpaq -method 69	6901 bytes	-299 bytes (-4.15%)
Burrows-Wheeler transform (Wikipedia)	bzip2	bzip2 -9	7127 bytes	-73 bytes (-1.01%)
Zstandard (Wikipedia)	zstd	zstd -19	7193 bytes	-7 bytes (-0.10%)
LZMA2 (Wikipedia)	xz	xz -9	7224 bytes	+24 bytes (+0.33%)

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.