Socket.IO 1.3.5 - as small as it gets (near-perfect GZIP compression)

Choose a version:

The original file has 173966 bytes (169.9k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 91538 bytes (89.4k, 53%).

After GZIP compression these minified files vary in size:

Boot	23745 bytes (23.2k)	CDN
gzip -6 (default)	23688 bytes (23.1k)	local copy
gzip -9	23583 bytes (23.0k)	local copy
libdeflate -12	22772 bytes (22.2k)	local copy
7zip -mx=9 -tgzip	22708 bytes (22.2k)	local copy
zultra	22703 bytes (22.2k)	local copy
kzip -s0 -rn -b0	22671 bytes (22.1k)	local copy
pigz -11 -n	22668 bytes (22.1k)	local copy
Zopfli	22651 bytes (22.1k)	local copy
cdnjs	20323 bytes (19.8k)	CDN

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/socketio/socket.io-1.3.5.min.js (or via HTTPS)

You will automatically get the smallest Socket.IO 1.3.5 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

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 --mls512 --bsr7 --lazy --ohh

(found July 4, 2016)

Description	Value	Parameter
iterations	100000	--i100000
maximum blocks	8	--mb8
maximum length score	512	--mls512
block splitting recursion	7	--bsr7
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/socketio/socket.io-client/1.3.5/socket.io.min.js --location | md5sum
38dc67c66183f4f3dc4af8eb5bb31300 -
curl --silent --compressed https://minime.stephan-brumme.com/files/socket.io/socket.io-1.3.5.min.zopfli.js.gz | md5sum
38dc67c66183f4f3dc4af8eb5bb31300 -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/socketio/socket.io-client/1.3.5/socket.io.min.js --location | sha1sum
95e44cbfd9951ea658db0856a43ddf5ed0796748 -
curl --silent --compressed https://minime.stephan-brumme.com/files/socket.io/socket.io-1.3.5.min.zopfli.js.gz | sha1sum
95e44cbfd9951ea658db0856a43ddf5ed0796748 -

CDN	Size (compressed)	MD5 (uncompressed)	Comment / Diff	Timestamp
Boot	23745 bytes	6553172c6dc3b4fa88b3d76b4eb148fc	< !function(e){if("object"==typeof exports&&"undefined"!=typ [...] < this.query=this.query\|\|{};if(!callbacks){if(!global.___eio [...] < output+=stringFromCharCode(value>>>10&1023\|55296);value=56 [...] > !function(t){if("object"==typeof exports&&"undefined"!=typ [...] > (!c\|\|e)&&(this.supportsBinary=!1),r.call(this,t)}var r=t(" [...] > if("null"==i.slice(P,P+4))return P+=4,null;q()}return"$"}, [...]	(invalid)
cdnjs	20323 bytes	6553172c6dc3b4fa88b3d76b4eb148fc	< !function(e){if("object"==typeof exports&&"undefined"!=typ [...] < this.query=this.query\|\|{};if(!callbacks){if(!global.___eio [...] < output+=stringFromCharCode(value>>>10&1023\|55296);value=56 [...] > !function(t){if("object"==typeof exports&&"undefined"!=typ [...] > (!c\|\|e)&&(this.supportsBinary=!1),r.call(this,t)}var r=t(" [...] > if("null"==i.slice(P,P+4))return P+=4,null;q()}return"$"}, [...]	(invalid)

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

Other Versions

Available Socket.IO versions at minime.stephan-brumme.com:

4.5.4, 4.5.3, 4.5.2, 4.5.1, 4.5.0, 4.4.1, 4.4.0, 4.3.2, 4.3.1, 4.3.0, 4.2.0, 4.1.3, 4.1.2, 4.1.1, 4.1.0, 4.0.2, 4.0.1, 4.0.0,
3.1.2, 3.1.1, 3.1.0, 3.0.5, 3.0.4, 3.0.3, 3.0.2, 3.0.1, 3.0.0,
2.4.0, 2.3.1, 2.3.0, 2.2.0, 2.1.1, 2.1.0, 2.0.4, 2.0.3, 2.0.2, 2.0.1, 2.0.0,
1.7.4, 1.7.2, 1.7.1, 1.7.0, 1.6.0, 1.5.0, 1.4.5, 1.4.4, 1.4.3, 1.4.2, 1.4.1, 1.4.0, 1.3.7, 1.3.6, 1.3.5, 1.3.4, 1.3.3, 1.3.2, 1.3.1, 1.3.0, 1.2.1, 1.2.0, 1.1.0, 1.0.6, 1.0.5, 1.0.4, 1.0.3, 1.0.2, 1.0.1, 1.0.0

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

Changelog

Best Zopfli parameters so far:

Size	Improvement	Parameters	Found
22651 bytes	-1 byte	zopfli --i100000 --mls512 --bsr7 --lazy --ohh	July 4, 2016 @ 12:18
22652 bytes	-1 byte	zopfli --i1000 --mls2048 --bsr40 --lazy --ohh	June 29, 2016 @ 17:27
22653 bytes	-1 byte	zopfli --i1000 --mls1024 --bsr17 --lazy --ohh	June 29, 2016 @ 17:14
22654 bytes	-1 byte	zopfli --i1000 --mls128 --bsr23 --lazy --ohh	June 29, 2016 @ 15:59
22655 bytes	–	zopfli --i100 --mls2048 --bsr25 --lazy --ohh	June 29, 2016 @ 13:25

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 @ 12:51.

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 100,000.

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	22658	22658	22658	22657	22657	22666	22657	22657	22661	22661	22669	22670	22670	22669	22668
4	22681	22682	22682	22682	22683	22663	22663	22662	22655	22655	22668	22668	22668	22668	22668
6	22654	22654	22655	22654	22654	22655	22654	22653	22653	22655	22653	22668	22669	22669	22669
7	22657	22659	22655	22655	22656	22654	22653	22654	22651	22653	22670	22667	22667	22669	22669
8	22654	22653	22654	22655	22653	22655	22654	22653	22656	22653	22669	22670	22669	22669	22669
9	22659	22660	22655	22654	22662	22665	22661	22653	22654	22655	22653	22667	22669	22668	22669
10	22658	22654	22660	22655	22660	22662	22660	22660	22654	22657	22659	22671	22669	22669	22668
11	22656	22658	22653	22654	22654	22662	22661	22660	22654	22653	22670	22670	22669	22668	22668
12	22653	22671	22661	22661	22654	22664	22653	22654	22654	22653	22670	22669	22667	22668	22669
13	22653	22653	22662	22654	22654	22655	22654	22653	22655	22657	22659	22668	22668	22668	22667
14	22659	22653	22654	22654	22656	22653	22653	22653	22654	22657	22655	22667	22669	22668	22673
15	22654	22655	22653	22655	22652	22655	22658	22655	22658	22653	22660	22668	22669	22669	22669
16	22658	22658	22660	22655	22661	22662	22660	22660	22651	22654	22656	22668	22668	22669	22668
17	22659	22653	22653	22654	22656	22656	22653	22654	22653	22652	22670	22669	22668	22668	22667
18	22659	22654	22653	22654	22654	22656	22654	22655	22654	22657	22670	22667	22668	22669	22669
19	22659	22657	22662	22654	22655	22655	22654	22654	22655	22653	22655	22668	22669	22669	22669
20	22667	22662	22661	22662	22660	22661	22661	22654	22654	22653	22654	22668	22669	22669	22669
21	22656	22656	22661	22661	22655	22655	22653	22654	22653	22653	22653	22669	22669	22668	22672
22	22657	22653	22654	22653	22658	22657	22653	22653	22654	22654	22670	22667	22669	22669	22669
23	22656	22654	22654	22655	22654	22654	22653	22654	22653	22653	22670	22667	22669	22668	22669
25	22658	22656	22663	22661	22656	22662	22653	22654	22653	22654	22653	22667	22669	22668	22669
30	22658	22659	22661	22654	22658	22657	22653	22653	22658	22655	22653	22670	22669	22669	22669
40	22659	22655	22654	22654	22652	22654	22654	22654	22657	22654	22652	22669	22669	22669	22669

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	22655 bytes	–	100%
1,000	22652 bytes	-3 bytes	100%
10,000	22652 bytes	–	100%
100,000	22651 bytes	-1 byte	1.74%
1,000,000	–	–	–
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)	22671 bytes	+20 bytes (+0.09%)	–
1	22692 bytes	+41 bytes (+0.18%)	+21 bytes
2	22676 bytes	+25 bytes (+0.11%)	+5 bytes
3	22719 bytes	+68 bytes (+0.30%)	+48 bytes
4	22745 bytes	+94 bytes (+0.41%)	+74 bytes
5	22781 bytes	+130 bytes (+0.57%)	+110 bytes
6	22810 bytes	+159 bytes (+0.70%)	+139 bytes
7	22843 bytes	+192 bytes (+0.85%)	+172 bytes
8	22843 bytes	+192 bytes (+0.85%)	+172 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
ZPAQ (Wikipedia)	zpaq	zpaq -method 69	18317 bytes	-4334 bytes (-19.13%)
RAR (proprietary)	RAR	rar a -m5 -md64m -mc63:128t -mt1	19325 bytes	-3326 bytes (-14.68%)
PPMd (Wikipedia)	7zip	7za a -mx=9 -m0=ppmd	20276 bytes	-2375 bytes (-10.49%)
Brotli (Wikipedia)	brotli	brotli -q 11	21370 bytes	-1281 bytes (-5.66%)
LZMA2 (Wikipedia)	xz	xz -9	22112 bytes	-539 bytes (-2.38%)
Burrows-Wheeler transform (Wikipedia)	bzip2	bzip2 -9	22317 bytes	-334 bytes (-1.47%)
Zstandard (Wikipedia)	zstd	zstd -19	22444 bytes	-207 bytes (-0.91%)

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 2024.
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.