Choose a version:
25% The original file has 162026 bytes (158.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 39823 bytes (38.9k, 25%).

After GZIP compression these minified files vary in size:
Boot
  15855 bytes (15.5k)
CDN, direct link
cdnjs
  13941 bytes (13.6k)
CDN, direct link
gzip -6 (default)
  13893 bytes (13.6k)
local copy
gzip -9
  13882 bytes (13.6k)
local copy
cdnhttps
  13861 bytes (13.5k)
CDN, direct link
7zip -mx=9 -tgzip
  13483 bytes (13.2k)
local copy
kzip -s0 -rn -b1
  13483 bytes (13.2k)
local copy
libdeflate -12
  13472 bytes (13.2k)
local copy
pigz -11 -n
  13453 bytes (13.1k)
local copy
Zopfli
  13434 bytes (13.1k)
local copy
Zopfli (defluff)
  13433 bytes (13.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/knockout/knockout-2.0.0.min.js

You will automatically get the smallest Knockout 2.0.0 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 427 bytes by using my Knockout 2.0.0 Zopfli version instead of the best available CDN (3.18% smaller than cdnhttps, 13434 vs. 13861 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 --i100000 --mb8 --mls64 --bsr9 --lazy --ohh

(found December 18, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 64  --mls64
block splitting recursion 9  --bsr9
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

Even Smaller Files Thanks To Defluff

Zopfli's output can be further optimized by the defluff tool.
In this particular case, defluff saves 1 more byte (13433 bytes).

Verify file integrity

After decompression, my uncompressed files are identical to the original ones:

MD5:
curl --silent --compressed http://knockoutjs.com/downloads/knockout-2.0.0.js --location | md5sum
88d6de08489039ca5e2aa6566849b0cc  -
curl --silent --compressed http://minime.stephan-brumme.com/files/knockout/knockout-2.0.0.min.zopfli.js.gz | md5sum
88d6de08489039ca5e2aa6566849b0cc  -

SHA1:
curl --silent --compressed http://knockoutjs.com/downloads/knockout-2.0.0.js --location | sha1sum
ec3e5fa9fc6f8f89262c4c0a83279ed63f465ee5  -
curl --silent --compressed http://minime.stephan-brumme.com/files/knockout/knockout-2.0.0.min.zopfli.js.gz | sha1sum
ec3e5fa9fc6f8f89262c4c0a83279ed63f465ee5  -

CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Boot 15855 bytes 6cd863a573e96c8792452bd4c57c5e28 only whitespaces differ (invalid)
cdnjs 13941 bytes 6cd863a573e96c8792452bd4c57c5e28 only whitespaces differ (invalid)
cdnhttps 13861 bytes 6cd863a573e96c8792452bd4c57c5e28 only whitespaces differ December 24, 2015 @ 07:33

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
13434 bytes -1 byte zopfli --i100000 --mls64 --bsr9 --lazy --ohh December 18, 2015 @ 22:51
13435 bytes -1 byte zopfli --i10000 --mls64 --bsr14 --lazy --ohh September 20, 2015 @ 08:42
13436 bytes -1 byte zopfli --i10000 --mls64 --bsr12 --lazy --ohh September 20, 2015 @ 08:39
13437 bytes -1 byte zopfli --i1000 --mls4096 --bsr9 --lazy --ohh September 10, 2015 @ 11:57
13438 bytes zopfli --i100 --mls4096 --bsr4 --lazy --ohh September 10, 2015 @ 11:37

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

Most recent activity on June 16, 2016 @ 14:40.

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
13439 13452 13451 13452 13457 13453 13456 13452 13455 13459 13458 13438 13447 13450 13452
13442 13454 13452 13439 13438 13451 13457 13449 13451 13442 13445 13434 13447 13455 13447
13438 13439 13450 13440 13457 13435 13437 13444 13446 13444 13445 13435 13437 13456 13438
13453 13452 13453 13457 13441 13450 13448 13457 13448 13449 13443 13436 13437 13445 13448
13453 13453 13452 13447 13447 13435 13457 13438 13444 13448 13452 13437 13437 13448 13450
13437 13453 13438 13441 13452 13434 13456 13456 13444 13444 13441 13437 13450 13445 13447
13456 13438 13455 13441 13442 13457 13439 13448 13454 13448 13438 13439 13456 13444 13448
13439 13446 13438 13441 13441 13450 13438 13437 13447 13444 13439 13437 13437 13447 13449
13440 13440 13437 13441 13444 13435 13443 13448 13448 13448 13443 13435 13437 13444 13448
13440 13439 13453 13437 13439 13434 13437 13437 13443 13444 13445 13435 13436 13447 13446
13455 13453 13453 13440 13441 13434 13434 13437 13445 13444 13443 13439 13455 13454 13437
13438 13453 13453 13435 13457 13450 13434 13441 13445 13444 13441 13437 13437 13449 13447
13442 13438 13437 13436 13442 13434 13435 13438 13446 13443 13443 13438 13450 13448 13447
13439 13438 13439 13439 13442 13451 13442 13448 13448 13443 13443 13435 13437 13450 13449
13439 13447 13437 13440 13440 13443 13444 13437 13444 13444 13443 13435 13437 13445 13450
13439 13438 13452 13437 13443 13437 13434 13443 13443 13443 13443 13438 13451 13445 13448
13440 13453 13452 13437 13441 13434 13442 13443 13445 13443 13443 13437 13437 13448 13448
13447 13453 13452 13452 13441 13437 13435 13456 13443 13443 13441 13438 13437 13444 13448
13437 13438 13437 13437 13442 13450 13443 13456 13443 13442 13440 13436 13456 13439 13447
13438 13438 13437 13438 13440 13435 13443 13438 13448 13444 13439 13437 13439 13445 13447
13440 13438 13438 13435 13443 13437 13443 13448 13443 13443 13443 13439 13456 13445 13446
13440 13445 13437 13438 13441 13436 13434 13437 13444 13444 13443 13437 13438 13448 13447
13440 13438 13437 13438 13440 13435 13436 13437 13445 13444 13437 13438 13439 13444 13447

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 13438 bytes 100%
1,000 13437 bytes -1 byte 100%
10,000 13435 bytes -2 bytes 100%
100,000 13434 bytes -1 byte 8.70%
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
13483 bytes +49 bytes (+0.36%)
13483 bytes +49 bytes (+0.36%)
13513 bytes +79 bytes (+0.59%) +30 bytes
13543 bytes +109 bytes (+0.81%) +60 bytes
13514 bytes +80 bytes (+0.60%) +31 bytes
13546 bytes +112 bytes (+0.83%) +63 bytes
13569 bytes +135 bytes (+1.00%) +86 bytes
13590 bytes +156 bytes (+1.16%) +107 bytes
13635 bytes +201 bytes (+1.50%) +152 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 11619 bytes -1815 bytes (-13.51%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 12074 bytes -1360 bytes (-10.12%)
Brotli (Wikipedia) brotli brotli -q 11 12286 bytes -1148 bytes (-8.55%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 12466 bytes -968 bytes (-7.21%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 13081 bytes -353 bytes (-2.63%)
LZMA2 (Wikipedia) xz xz -9 13284 bytes -150 bytes (-1.12%)
ZSTD (Wikipedia) zstd zstd -19 13442 bytes +8 bytes (+0.06%)

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