Choose a version:
39% The original file has 219227 bytes (214.1k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 85925 bytes (83.9k, 39%).

After GZIP compression these minified files vary in size:
Microsoft
  38182 bytes (37.3k)
CDN
Baidu
  30205 bytes (29.5k)
CDN
gzip -6 (default)
  29967 bytes (29.3k)
local copy
Google
  29947 bytes (29.2k)
CDN
gzip -9
  29890 bytes (29.2k)
local copy
libdeflate -12
  28910 bytes (28.2k)
local copy
kzip -s0 -rn -b0
  28901 bytes (28.2k)
local copy
7zip -mx=9 -tgzip
  28887 bytes (28.2k)
local copy
Yandex
  28821 bytes (28.1k)
CDN
pigz -11 -n
  28815 bytes (28.1k)
local copy
Zopfli
  28790 bytes (28.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/jquery/jquery-1.5.2.min.js (or via HTTPS)

You will automatically get the smallest jQuery 1.5.2 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 31 bytes by using my jQuery 1.5.2 Zopfli version instead of the best available CDN (0.11% smaller than Yandex, 28790 vs. 28821 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 --mls32 --bsr12 --lazy --ohh

(found January 8, 2016)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 32  --mls32
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

Verify file integrity

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

MD5:
curl --silent --compressed https://code.jquery.com/jquery-1.5.2.min.js --location | md5sum
e85aed5c30d734f1e30646e030d7a817  -
curl --silent --compressed https://minime.stephan-brumme.com/files/jquery/jquery-1.5.2.min.zopfli.js.gz | md5sum
e85aed5c30d734f1e30646e030d7a817  -

SHA1:
curl --silent --compressed https://code.jquery.com/jquery-1.5.2.min.js --location | sha1sum
b8dcaa1c866905c0bdb0b70c8e564ff1c3fe27ad  -
curl --silent --compressed https://minime.stephan-brumme.com/files/jquery/jquery-1.5.2.min.zopfli.js.gz | sha1sum
b8dcaa1c866905c0bdb0b70c8e564ff1c3fe27ad  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 38182 bytes e85aed5c30d734f1e30646e030d7a817 (invalid)
Google 29947 bytes e85aed5c30d734f1e30646e030d7a817 (invalid)
Yandex 28821 bytes e85aed5c30d734f1e30646e030d7a817 June 15, 2015 @ 21:17

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 30205 bytes c580234a054e07276cbedbe2993a2378 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
28790 bytes -1 byte zopfli --i100000 --mls32 --bsr12 --lazy --ohh January 8, 2016 @ 10:28
28791 bytes -1 byte zopfli --i100000 --mls32 --bsr30 --lazy --ohh January 8, 2016 @ 08:53
28792 bytes -1 byte zopfli --i100000 --mls8 --bsr16 --lazy --ohh November 23, 2015 @ 11:26
28793 bytes -3 bytes zopfli --i100000 --mls4096 --bsr14 --lazy --ohh September 2, 2015 @ 00:30
28796 bytes -2 bytes zopfli --i10000 --mls4096 --bsr14 --lazy --ohh September 1, 2015 @ 21:30
28798 bytes -3 bytes zopfli --i1000 --mls4096 --bsr14 --lazy --ohh September 1, 2015 @ 20:38
28801 bytes -4 bytes zopfli --i1000 --mls8192 --bsr10 --lazy --ohh September 1, 2015 @ 20:38
28805 bytes zopfli --i100 --mls8192 --bsr10 --lazy --ohh September 1, 2015 @ 20:27

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
28811 28810 28810 28809 28806 28807 28803 28812 28803 28813 28798 28801 28800 28800 28808
28799 28795 28794 28794 28796 28795 28799 28801 28807 28801 28802 28801 28798 28804 28806
28795 28803 28795 28795 28795 28797 28794 28802 28799 28799 28804 28800 28800 28804 28804
28801 28800 28802 28802 28799 28802 28804 28801 28799 28799 28799 28797 28798 28796 28799
28796 28796 28799 28801 28795 28794 28798 28804 28799 28799 28799 28800 28802 28802 28804
28810 28795 28792 28794 28794 28797 28792 28800 28798 28798 28800 28801 28802 28800 28804
28806 28802 28799 28796 28797 28797 28803 28800 28803 28799 28799 28799 28795 28798 28799
28801 28796 28799 28795 28796 28795 28798 28804 28799 28799 28802 28799 28802 28800 28804
28794 28795 28795 28795 28790 28799 28791 28798 28799 28799 28802 28796 28799 28796 28800
28794 28800 28801 28795 28796 28796 28792 28803 28799 28799 28804 28795 28797 28796 28803
28800 28792 28800 28795 28794 28794 28797 28803 28799 28799 28800 28793 28804 28800 28800
28800 28796 28799 28794 28797 28798 28794 28798 28803 28799 28799 28796 28803 28800 28806
28794 28796 28792 28795 28794 28796 28792 28804 28804 28799 28800 28799 28802 28800 28805
28800 28801 28800 28795 28795 28797 28805 28798 28800 28799 28800 28802 28803 28800 28802
28807 28794 28795 28794 28794 28798 28794 28798 28799 28799 28800 28799 28800 28800 28804
28807 28799 28799 28794 28799 28800 28802 28804 28799 28799 28800 28801 28805 28798 28805
28807 28800 28800 28801 28799 28798 28802 28804 28801 28800 28805 28797 28799 28804 28799
28799 28800 28794 28795 28795 28797 28804 28801 28799 28799 28798 28801 28797 28795 28798
28804 28798 28800 28803 28795 28801 28813 28802 28799 28799 28800 28799 28801 28800 28799
28807 28800 28800 28797 28796 28794 28798 28804 28800 28800 28799 28800 28803 28795 28799
28794 28795 28800 28795 28795 28796 28804 28798 28799 28799 28798 28799 28804 28795 28804
28796 28796 28799 28795 28791 28795 28806 28801 28803 28799 28799 28801 28805 28800 28805
28797 28795 28800 28801 28790 28794 28794 28799 28803 28799 28800 28799 28799 28800 28803

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 28801 bytes 100%
1,000 28793 bytes -8 bytes 100%
10,000 28793 bytes 100%
100,000 28790 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
28901 bytes +111 bytes (+0.39%)
28901 bytes +111 bytes (+0.39%)
28944 bytes +154 bytes (+0.53%) +43 bytes
28935 bytes +145 bytes (+0.50%) +34 bytes
28936 bytes +146 bytes (+0.51%) +35 bytes
28975 bytes +185 bytes (+0.64%) +74 bytes
28993 bytes +203 bytes (+0.71%) +92 bytes
29001 bytes +211 bytes (+0.73%) +100 bytes
29020 bytes +230 bytes (+0.80%) +119 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 23265 bytes -5525 bytes (-19.19%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 23917 bytes -4873 bytes (-16.93%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 25156 bytes -3634 bytes (-12.62%)
Brotli (Wikipedia) brotli brotli -q 11 26537 bytes -2253 bytes (-7.83%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 26774 bytes -2016 bytes (-7.00%)
LZMA2 (Wikipedia) xz xz -9 27704 bytes -1086 bytes (-3.77%)
Zstandard (Wikipedia) zstd zstd -19 28289 bytes -501 bytes (-1.74%)

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