Choose a version:
58% The original file has 80469 bytes (78.6k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 46437 bytes (45.3k, 58%).

After GZIP compression these minified files vary in size:
gzip -6 (default)
  14661 bytes (14.3k)
local copy
gzip -9
  14617 bytes (14.3k)
local copy
libdeflate -12
  14132 bytes (13.8k)
local copy
kzip -s0 -rn -b0
  14123 bytes (13.8k)
local copy
7zip -mx=9 -tgzip
  14097 bytes (13.8k)
local copy
pigz -11 -n
  14077 bytes (13.7k)
local copy
Zopfli
  14057 bytes (13.7k)
local copy
Zopfli (defluff)
  14056 bytes (13.7k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/jquery/jquery-1.2.1.min.js

You will automatically get the smallest jQuery 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

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 --bsr12 --lazy --ohh

(found January 5, 2016)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 8  --mls8
block splitting recursion 12  --bsr12
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 (14056 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed http://code.jquery.com/jquery-1.2.1.min.js --location | md5sum
1fd52f46e191c7d4234e48f759a64777  -
curl --silent --compressed http://minime.stephan-brumme.com/files/jquery/jquery-1.2.1.min.zopfli.js.gz | md5sum
1fd52f46e191c7d4234e48f759a64777  -

SHA1:
curl --silent --compressed http://code.jquery.com/jquery-1.2.1.min.js --location | sha1sum
0cafb88edcaebad82c207cdf124de1889364c9f3  -
curl --silent --compressed http://minime.stephan-brumme.com/files/jquery/jquery-1.2.1.min.zopfli.js.gz | sha1sum
0cafb88edcaebad82c207cdf124de1889364c9f3  -

Other Versions

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

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
14057 bytes -2 bytes zopfli --i100000 --mls8 --bsr12 --lazy --ohh January 5, 2016 @ 12:56
14059 bytes -2 bytes zopfli --i100000 --mls512 --bsr16 --lazy --ohh September 2, 2015 @ 02:48
14061 bytes -1 byte zopfli --i10000 --mls512 --bsr16 --lazy --ohh September 1, 2015 @ 21:37
14062 bytes -2 bytes zopfli --i1000 --mls512 --bsr16 --lazy --ohh September 1, 2015 @ 20:40
14064 bytes -1 byte zopfli --i1000 --mls2048 --bsr9 --lazy --ohh September 1, 2015 @ 20:40
14065 bytes zopfli --i100 --mls512 --bsr16 --lazy --ohh September 1, 2015 @ 20:17

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 @ 14:39.

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
14070 14070 14071 14072 14070 14071 14074 14068 14072 14081 14074 14082 14070 14073 14071
14075 14075 14069 14068 14064 14068 14070 14075 14071 14069 14061 14068 14076 14078 14070
14063 14065 14069 14064 14063 14063 14079 14065 14064 14069 14063 14073 14080 14076 14068
14061 14063 14062 14064 14063 14064 14065 14067 14061 14069 14062 14069 14083 14065 14065
14061 14062 14070 14063 14064 14063 14063 14064 14063 14070 14064 14069 14079 14075 14074
14062 14063 14062 14063 14063 14062 14063 14062 14063 14070 14060 14067 14069 14069 14081
14068 14068 14070 14073 14072 14062 14063 14063 14069 14071 14069 14069 14069 14076 14073
14070 14063 14069 14063 14064 14062 14062 14063 14060 14070 14060 14069 14078 14069 14064
14062 14063 14057 14063 14063 14063 14080 14081 14077 14078 14073 14069 14078 14073 14077
14062 14064 14062 14063 14062 14064 14063 14063 14059 14064 14063 14069 14071 14070 14065
14079 14064 14084 14062 14064 14085 14079 14064 14060 14070 14070 14073 14078 14070 14071
14062 14064 14062 14062 14063 14066 14064 14062 14062 14069 14069 14069 14078 14065 14063
14063 14063 14061 14062 14064 14064 14064 14061 14059 14065 14068 14069 14071 14068 14063
14062 14063 14070 14062 14064 14062 14079 14063 14062 14070 14076 14069 14069 14069 14072
14063 14064 14061 14063 14063 14064 14063 14064 14062 14069 14062 14069 14079 14075 14072
14064 14064 14061 14063 14063 14063 14063 14063 14061 14070 14070 14069 14069 14076 14076
14061 14063 14065 14063 14064 14071 14063 14063 14063 14070 14070 14069 14078 14070 14069
14059 14063 14060 14063 14063 14062 14062 14063 14064 14068 14069 14069 14079 14072 14070
14061 14072 14062 14064 14062 14063 14063 14063 14064 14070 14067 14069 14077 14070 14074
14071 14062 14071 14071 14064 14062 14062 14063 14062 14070 14069 14074 14079 14076 14071
14063 14063 14072 14062 14063 14061 14071 14069 14069 14070 14069 14075 14078 14070 14073
14058 14065 14062 14061 14062 14063 14062 14062 14063 14070 14062 14069 14078 14071 14063
14062 14064 14059 14071 14063 14064 14063 14065 14062 14071 14069 14068 14079 14070 14064

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 14064 bytes 100%
1,000 14061 bytes -3 bytes 100%
10,000 14060 bytes -1 byte 100%
100,000 14057 bytes -3 bytes 3.19%
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
14123 bytes +66 bytes (+0.47%)
14124 bytes +67 bytes (+0.48%) +1 byte
14125 bytes +68 bytes (+0.48%) +2 bytes
14143 bytes +86 bytes (+0.61%) +20 bytes
14157 bytes +100 bytes (+0.71%) +34 bytes
14156 bytes +99 bytes (+0.70%) +33 bytes
14181 bytes +124 bytes (+0.88%) +58 bytes
14230 bytes +173 bytes (+1.23%) +107 bytes
14255 bytes +198 bytes (+1.41%) +132 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 12174 bytes -1883 bytes (-13.40%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 12237 bytes -1820 bytes (-12.95%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 12996 bytes -1061 bytes (-7.55%)
Brotli (Wikipedia) brotli brotli -q 11 13313 bytes -744 bytes (-5.29%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 13800 bytes -257 bytes (-1.83%)
LZMA2 (Wikipedia) xz xz -9 14000 bytes -57 bytes (-0.41%)
ZSTD (Wikipedia) zstd zstd -19 14101 bytes +44 bytes (+0.31%)

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