Choose a version:
44% The original file has 163855 bytes (160.0k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 72174 bytes (70.5k, 44%).

After GZIP compression these minified files vary in size:
Microsoft
  31254 bytes (30.5k)
CDN
Boot
  28573 bytes (27.9k)
CDN
Baidu
  24836 bytes (24.3k)
CDN
cdnjs
  24751 bytes (24.2k)
CDN
gzip -6 (default)
  24625 bytes (24.0k)
local copy
Google
  24605 bytes (24.0k)
CDN
cdnhttps
  24605 bytes (24.0k)
CDN
gzip -9
  24575 bytes (24.0k)
local copy
7zip -mx=9 -tgzip
  23869 bytes (23.3k)
local copy
kzip -s0 -rn -b5
  23833 bytes (23.3k)
local copy
libdeflate -12
  23799 bytes (23.2k)
local copy
Yandex
  23793 bytes (23.2k)
CDN
pigz -11 -n
  23781 bytes (23.2k)
local copy
Zopfli
  23745 bytes (23.2k)
local copy
Zopfli (defluff)
  23743 bytes (23.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/jquery/jquery-1.4.2.min.js (or via HTTPS)

You will automatically get the smallest jQuery 1.4.2 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 48 bytes by using my jQuery 1.4.2 Zopfli version instead of the best available CDN (0.20% smaller than Yandex, 23745 vs. 23793 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 --mls8 --bsr16 --lazy --ohh

(found October 21, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 8  --mls8
block splitting recursion 16  --bsr16
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 2 more bytes (23743 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed https://code.jquery.com/jquery-1.4.2.min.js --location | md5sum
10092eee563dec2dca82b77d2cf5a1ae  -
curl --silent --compressed https://minime.stephan-brumme.com/files/jquery/jquery-1.4.2.min.zopfli.js.gz | md5sum
10092eee563dec2dca82b77d2cf5a1ae  -

SHA1:
curl --silent --compressed https://code.jquery.com/jquery-1.4.2.min.js --location | sha1sum
65cbff4e9d95d47a6f31d96ab4ea361c1f538a7b  -
curl --silent --compressed https://minime.stephan-brumme.com/files/jquery/jquery-1.4.2.min.zopfli.js.gz | sha1sum
65cbff4e9d95d47a6f31d96ab4ea361c1f538a7b  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 28573 bytes 10092eee563dec2dca82b77d2cf5a1ae March 18, 2015 @ 09:41
cdnjs 24751 bytes 10092eee563dec2dca82b77d2cf5a1ae (invalid)
Google 24605 bytes 10092eee563dec2dca82b77d2cf5a1ae (invalid)
cdnhttps 24605 bytes 10092eee563dec2dca82b77d2cf5a1ae December 24, 2015 @ 07:33
Yandex 23793 bytes 10092eee563dec2dca82b77d2cf5a1ae June 15, 2015 @ 21:17

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Microsoft 31254 bytes e055c570668301b71137281a0ce65560 < /*!
> /*
< * http://jquery.com/
< *
< * Copyright 2010, John Resig
< * Dual licensed under the MIT or GPL Version 2 licenses.
< * http://jquery.org/license
> * Copyright 2010, John Resig, http://jquery.com/
> * Distributed in whole under the terms of the MIT license
> * http://www.opensource.org/licenses/mit-license.php
[...]
(invalid)
Baidu 24836 bytes 65b352e1ba79f0e2a3b1e014bc2571af only whitespaces differ January 7, 2015 @ 10:16

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

Other Versions

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

3.3.1, 3.3.0,
3.2.1, 3.2.0,
3.1.1, 3.1.0,
3.0.0,
2.2.4, 2.2.3, 2.2.2, 2.2.1, 2.2.0,
2.1.4, 2.1.3, 2.1.2, 2.1.1, 2.1.0,
2.0.3, 2.0.2, 2.0.1, 2.0.0,
1.12.4, 1.12.3, 1.12.2, 1.12.1, 1.12.0,
1.11.3, 1.11.2, 1.11.1, 1.11.0,
1.10.2, 1.10.1, 1.10.0,
1.9.1, 1.9.0,
1.8.3, 1.8.2, 1.8.1, 1.8.0,
1.7.2, 1.7.1, 1.7.0,
1.6.4, 1.6.3, 1.6.2, 1.6.1, 1.6,
1.5.2, 1.5.1, 1.5,
1.4.4, 1.4.3, 1.4.2, 1.4.1, 1.4,
1.3.2, 1.3.1, 1.3,
1.2.6, 1.2.5, 1.2.4, 1.2.3, 1.2.2, 1.2.1, 1.2,
1.1.4, 1.1.3, 1.1.2, 1.1.1, 1.1,
1.0.4, 1.0.3, 1.0.2, 1.0.1, 1.0

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

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
23745 bytes -2 bytes zopfli --i100000 --mls8 --bsr16 --lazy --ohh October 21, 2015 @ 12:03
23747 bytes -2 bytes zopfli --i10000 --mls8 --bsr16 --lazy --ohh October 21, 2015 @ 11:32
23749 bytes -5 bytes zopfli --i1000 --mls8 --bsr16 --lazy --ohh September 19, 2015 @ 23:44
23754 bytes zopfli --i100 --mls8 --bsr16 --lazy --ohh September 18, 2015 @ 16:18

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 @ 14:36.

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
23773 23773 23773 23773 23773 23774 23773 23774 23774 23776 23777 23777 23775 23773 23778
23778 23777 23778 23774 23779 23774 23773 23776 23773 23772 23777 23779 23780 23781 23781
23778 23776 23778 23778 23778 23773 23779 23773 23774 23773 23773 23780 23782 23783 23781
23779 23778 23772 23775 23776 23773 23777 23776 23774 23773 23773 23775 23774 23773 23774
23774 23774 23773 23774 23773 23774 23773 23774 23770 23776 23777 23773 23781 23779 23781
23776 23776 23778 23776 23775 23776 23774 23773 23774 23773 23774 23779 23782 23773 23784
23777 23777 23777 23778 23776 23777 23777 23778 23774 23778 23773 23773 23780 23772 23782
23776 23778 23776 23776 23774 23775 23774 23773 23770 23774 23774 23779 23773 23774 23776
23773 23772 23774 23772 23774 23774 23778 23774 23772 23773 23777 23772 23780 23773 23785
23776 23777 23774 23778 23774 23775 23777 23770 23773 23773 23777 23780 23780 23781 23780
23776 23776 23776 23778 23777 23777 23777 23778 23774 23778 23777 23779 23777 23773 23783
23777 23777 23776 23778 23775 23777 23778 23773 23774 23778 23773 23775 23780 23773 23776
23777 23777 23745 23774 23774 23775 23774 23773 23774 23773 23776 23774 23780 23779 23785
23777 23777 23777 23778 23774 23773 23779 23773 23774 23774 23773 23777 23780 23771 23785
23777 23772 23777 23777 23774 23775 23774 23778 23774 23773 23775 23780 23781 23773 23785
23777 23777 23776 23776 23776 23775 23779 23775 23773 23773 23773 23775 23772 23773 23780
23773 23774 23776 23775 23777 23776 23775 23774 23773 23773 23774 23773 23776 23774 23780
23773 23774 23775 23775 23773 23778 23776 23773 23773 23774 23774 23781 23780 23779 23779
23772 23772 23773 23774 23773 23778 23774 23774 23773 23774 23774 23773 23771 23772 23779
23774 23774 23776 23772 23774 23776 23776 23774 23773 23774 23777 23773 23780 23773 23783
23773 23774 23774 23774 23772 23777 23778 23774 23772 23774 23774 23774 23781 23774 23781
23773 23773 23773 23772 23776 23775 23779 23773 23774 23774 23777 23775 23780 23777 23781
23774 23774 23773 23776 23775 23775 23773 23774 23774 23774 23774 23780 23775 23774 23781

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 23754 bytes 100%
1,000 23749 bytes -5 bytes 100%
10,000 23747 bytes -2 bytes 100%
100,000 23745 bytes -2 bytes 0.58%
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
23841 bytes +96 bytes (+0.40%) +8 bytes
23841 bytes +96 bytes (+0.40%) +8 bytes
23871 bytes +126 bytes (+0.53%) +38 bytes
23860 bytes +115 bytes (+0.48%) +27 bytes
23835 bytes +90 bytes (+0.38%) +2 bytes
23833 bytes +88 bytes (+0.37%)
23861 bytes +116 bytes (+0.49%) +28 bytes
23867 bytes +122 bytes (+0.51%) +34 bytes
23899 bytes +154 bytes (+0.65%) +66 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
ZPAQ (Wikipedia) zpaq zpaq -method 69 19715 bytes -4030 bytes (-16.97%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 20099 bytes -3646 bytes (-15.35%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 20872 bytes -2873 bytes (-12.10%)
Brotli (Wikipedia) brotli brotli -q 11 21942 bytes -1803 bytes (-7.59%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 22643 bytes -1102 bytes (-4.64%)
LZMA2 (Wikipedia) xz xz -9 23080 bytes -665 bytes (-2.80%)
Zstandard (Wikipedia) zstd zstd -19 23466 bytes -279 bytes (-1.17%)

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 2018.
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