Choose a version:
21% The original file has 286716 bytes (280.0k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 59822 bytes (58.4k, 21%).

After GZIP compression these minified files vary in size:
Boot
  25328 bytes (24.7k)
CDN, direct link
cdnjs
  22278 bytes (21.8k)
CDN, direct link
gzip -6 (default)
  22115 bytes (21.6k)
local copy
unpkg
  22094 bytes (21.6k)
CDN, direct link
cdnhttps
  22093 bytes (21.6k)
CDN, direct link
gzip -9
  22065 bytes (21.5k)
local copy
jsdelivr
  22052 bytes (21.5k)
CDN, direct link
7zip -mx=9 -tgzip
  21385 bytes (20.9k)
local copy
libdeflate -12
  21365 bytes (20.9k)
local copy
kzip -s0 -rn -b4
  21360 bytes (20.9k)
local copy
pigz -11 -n
  21344 bytes (20.8k)
local copy
Zopfli
  21321 bytes (20.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/knockout/knockout-3.4.0.min.js

You will automatically get the smallest Knockout 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 731 bytes by using my Knockout 3.4.0 Zopfli version instead of the best available CDN (3.43% smaller than jsdelivr, 21321 vs. 22052 bytes):
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 --i10000000 --mb8 --mls32768 --bsr40 --lazy --ohh

(found January 9, 2016)
Description Value Parameter
iterations 10000000  --i10000000
maximum blocks 8  --mb8
maximum length score 32768  --mls32768
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 http://knockoutjs.com/downloads/knockout-3.4.0.js --location | md5sum
fa8662c7a8415d0355f444eaff534845  -
curl --silent --compressed http://minime.stephan-brumme.com/files/knockout/knockout-3.4.0.min.zopfli.js.gz | md5sum
fa8662c7a8415d0355f444eaff534845  -

SHA1:
curl --silent --compressed http://knockoutjs.com/downloads/knockout-3.4.0.js --location | sha1sum
b60c2c301c280378b4d51769cb20a46e65989c73  -
curl --silent --compressed http://minime.stephan-brumme.com/files/knockout/knockout-3.4.0.min.zopfli.js.gz | sha1sum
b60c2c301c280378b4d51769cb20a46e65989c73  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 25328 bytes fa8662c7a8415d0355f444eaff534845 November 29, 2015 @ 08:56
cdnjs 22278 bytes fa8662c7a8415d0355f444eaff534845 November 17, 2015 @ 02:20
unpkg 22094 bytes fa8662c7a8415d0355f444eaff534845 July 11, 2016 @ 16:43
cdnhttps 22093 bytes fa8662c7a8415d0355f444eaff534845 December 24, 2015 @ 07:33
jsdelivr 22052 bytes fa8662c7a8415d0355f444eaff534845 November 17, 2015 @ 10:19

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

Other Versions

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

3.4.2, 3.4.1, 3.4.0,
3.3.0,
3.2.0,
3.1.0,
3.0.0,
2.3.0,
2.2.1, 2.2.0,
2.1.0,
2.0.0,
1.2.1, 1.2.0,
1.1.2, 1.1.1, 1.1.0

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

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
21321 bytes -1 byte zopfli --i10000000 --mls32768 --bsr40 --lazy --ohh January 9, 2016 @ 16:48
21322 bytes -3 bytes zopfli --i1000000 --mls32768 --bsr40 --lazy --ohh November 17, 2015 @ 20:35
21325 bytes -1 byte zopfli --i100000 --mls32768 --bsr40 --lazy --ohh November 17, 2015 @ 11:59
21326 bytes -2 bytes zopfli --i10000 --mls32768 --bsr40 --lazy --ohh November 17, 2015 @ 11:25
21328 bytes -1 byte zopfli --i10000 --mls4096 --bsr18 --lazy --ohh November 17, 2015 @ 10:21
21329 bytes -1 byte zopfli --i1000 --mls4096 --bsr21 --lazy --ohh November 17, 2015 @ 10:18
21330 bytes zopfli --i100 --mls4096 --bsr21 --lazy --ohh November 17, 2015 @ 08:53

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

Most recent activity on July 11, 2016 @ 16:43.

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, 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
21344 21343 21336 21338 21339 21340 21342 21342 21339 21337 21338 21330 21331 21337 21334
21335 21340 21336 21334 21334 21339 21341 21340 21339 21340 21339 21333 21326 21331 21329
21335 21334 21331 21334 21339 21339 21340 21340 21336 21340 21337 21331 21330 21330 21331
21332 21341 21336 21332 21334 21339 21341 21341 21339 21340 21339 21326 21330 21331 21330
21335 21341 21336 21332 21336 21339 21341 21340 21340 21340 21340 21329 21330 21335 21331
21337 21341 21331 21333 21339 21340 21341 21339 21340 21335 21339 21329 21329 21331 21329
21342 21342 21341 21339 21339 21339 21340 21339 21341 21326 21339 21329 21330 21332 21324
21336 21341 21336 21331 21337 21338 21342 21339 21339 21340 21339 21326 21330 21330 21326
21336 21340 21336 21333 21337 21340 21342 21341 21340 21340 21339 21330 21329 21335 21330
21338 21341 21341 21340 21334 21339 21340 21341 21338 21339 21339 21326 21327 21331 21329
21334 21341 21336 21340 21339 21339 21339 21340 21338 21338 21338 21330 21327 21330 21329
21337 21341 21336 21335 21334 21341 21341 21341 21339 21335 21338 21329 21330 21331 21329
21337 21341 21337 21334 21334 21341 21341 21339 21337 21339 21338 21329 21330 21335 21326
21335 21341 21336 21334 21333 21340 21339 21339 21339 21340 21339 21329 21330 21331 21326
21336 21333 21335 21333 21335 21340 21341 21341 21340 21339 21339 21326 21329 21332 21329
21338 21340 21335 21334 21334 21339 21340 21342 21340 21337 21339 21326 21329 21332 21330
21335 21341 21331 21342 21334 21340 21342 21340 21340 21339 21339 21330 21329 21331 21326
21335 21340 21336 21334 21334 21339 21342 21339 21340 21339 21339 21329 21329 21335 21331
21336 21341 21331 21334 21340 21340 21341 21339 21339 21327 21339 21329 21330 21339 21329
21338 21341 21331 21335 21335 21341 21342 21340 21339 21339 21339 21329 21327 21329 21329
21336 21341 21336 21332 21334 21340 21341 21339 21340 21326 21337 21329 21330 21335 21329
21334 21341 21335 21333 21335 21338 21341 21340 21340 21326 21339 21326 21330 21331 21329
21336 21336 21336 21334 21334 21340 21339 21339 21340 21340 21339 21332 21329 21330 21321

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 21330 bytes 100%
1,000 21328 bytes -2 bytes 100%
10,000 21326 bytes -2 bytes 100%
100,000 21325 bytes -1 byte 5.80%
1,000,000 21322 bytes -3 bytes 0.58%
10,000,000 21321 bytes -1 byte 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
21429 bytes +108 bytes (+0.51%) +69 bytes
21428 bytes +107 bytes (+0.50%) +68 bytes
21365 bytes +44 bytes (+0.21%) +5 bytes
21376 bytes +55 bytes (+0.26%) +16 bytes
21360 bytes +39 bytes (+0.18%)
21391 bytes +70 bytes (+0.33%) +31 bytes
21442 bytes +121 bytes (+0.57%) +82 bytes
21482 bytes +161 bytes (+0.76%) +122 bytes
21509 bytes +188 bytes (+0.88%) +149 bytes

Non-DEFLATE Algorithms

Archivers based on completely different compression algorithms often produce superior results.
Unfortunately, browsers only support gzip compression at the moment.
Algorithm Program Parameters Size Compared To Best Zopfli
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 18063 bytes -3258 bytes (-15.28%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 18113 bytes -3208 bytes (-15.05%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 19366 bytes -1955 bytes (-9.17%)
Brotli (Wikipedia) brotli brotli -q 11 19640 bytes -1681 bytes (-7.88%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 20180 bytes -1141 bytes (-5.35%)
LZMA2 (Wikipedia) xz xz -9 20868 bytes -453 bytes (-2.12%)
ZSTD (Wikipedia) zstd zstd -19 21257 bytes -64 bytes (-0.30%)

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):


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 2017.
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