Choose a version:
35% The original file has 268381 bytes (262.1k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 92629 bytes (90.5k, 35%).

After GZIP compression these minified files vary in size:
Microsoft
  41473 bytes (40.5k)
CDN, direct link
Boot
  37959 bytes (37.1k)
CDN, direct link
jsdelivr
  37959 bytes (37.1k)
CDN, direct link
Baidu
  33001 bytes (32.2k)
CDN, direct link
cdnjs
  32993 bytes (32.2k)
CDN, direct link
gzip -6 (default)
  32839 bytes (32.1k)
local copy
Google
  32819 bytes (32.0k)
CDN, direct link
cdnhttps
  32819 bytes (32.0k)
CDN, direct link
gzip -9
  32792 bytes (32.0k)
local copy
Sina
  32775 bytes (32.0k)
CDN, direct link
libdeflate -12
  31807 bytes (31.1k)
local copy
7zip -mx=9 -tgzip
  31763 bytes (31.0k)
local copy
kzip -s0 -rn -b2
  31755 bytes (31.0k)
local copy
Yandex
  31691 bytes (30.9k)
CDN, direct link
pigz -11 -n
  31679 bytes (30.9k)
local copy
Zopfli
  31668 bytes (30.9k)
local copy
Zopfli (defluff)
  31667 bytes (30.9k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/jquery/jquery-1.9.1.min.js

You will automatically get the smallest jQuery 1.9.1 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

Save 23 bytes by using my jQuery 1.9.1 Zopfli version instead of the best available CDN (0.07% smaller than Yandex, 31668 vs. 31691 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 --i1000000 --mb8 --mls2048 --bsr16 --lazy --ohh

(found September 8, 2015)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 2048  --mls2048
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 1 more byte (31667 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed http://code.jquery.com/jquery-1.9.1.min.js --location | md5sum
397754ba49e9e0cf4e7c190da78dda05  -
curl --silent --compressed http://minime.stephan-brumme.com/files/jquery/jquery-1.9.1.min.zopfli.js.gz | md5sum
397754ba49e9e0cf4e7c190da78dda05  -

SHA1:
curl --silent --compressed http://code.jquery.com/jquery-1.9.1.min.js --location | sha1sum
ae49e56999d82802727455f0ba83b63acd90a22b  -
curl --silent --compressed http://minime.stephan-brumme.com/files/jquery/jquery-1.9.1.min.zopfli.js.gz | sha1sum
ae49e56999d82802727455f0ba83b63acd90a22b  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 41473 bytes 397754ba49e9e0cf4e7c190da78dda05 (invalid)
Boot 37959 bytes 397754ba49e9e0cf4e7c190da78dda05 March 18, 2015 @ 09:42
jsdelivr 37959 bytes 397754ba49e9e0cf4e7c190da78dda05 (invalid)
cdnjs 32993 bytes 397754ba49e9e0cf4e7c190da78dda05 (invalid)
Google 32819 bytes 397754ba49e9e0cf4e7c190da78dda05 (invalid)
cdnhttps 32819 bytes 397754ba49e9e0cf4e7c190da78dda05 December 24, 2015 @ 07:33
Sina 32775 bytes 397754ba49e9e0cf4e7c190da78dda05 (invalid)
Yandex 31691 bytes 397754ba49e9e0cf4e7c190da78dda05 June 15, 2015 @ 21:17

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 33001 bytes 383771ef1692bfcc3f2b6917ca985778 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:

3.2.1, 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
31668 bytes -1 byte zopfli --i1000000 --mls2048 --bsr16 --lazy --ohh September 8, 2015 @ 02:09
31669 bytes -3 bytes zopfli --i100000 --mls2048 --bsr16 --lazy --ohh September 2, 2015 @ 00:05
31672 bytes -1 byte zopfli --i10000 --mls2048 --bsr16 --lazy --ohh September 1, 2015 @ 21:08
31673 bytes -1 byte zopfli --i1000 --mls2048 --bsr16 --lazy --ohh September 1, 2015 @ 20:35
31674 bytes zopfli --i100 --mls2048 --bsr16 --lazy --ohh September 1, 2015 @ 20:19

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, 100,000 or 1,000,000.
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
31676 31686 31687 31688 31681 31689 31678 31691 31679 31684 31685 31681 31681 31682 31680
31675 31676 31677 31683 31680 31679 31681 31681 31678 31677 31678 31672 31673 31676 31677
31673 31674 31672 31677 31672 31673 31673 31673 31680 31670 31670 31673 31672 31674 31677
31672 31675 31676 31676 31672 31672 31681 31673 31679 31673 31689 31680 31668 31675 31675
31673 31674 31673 31673 31672 31672 31673 31673 31677 31677 31673 31673 31672 31678 31678
31669 31674 31678 31674 31673 31673 31674 31673 31674 31671 31678 31673 31672 31675 31675
31673 31674 31677 31676 31672 31672 31674 31673 31677 31671 31682 31673 31672 31675 31675
31672 31674 31677 31676 31670 31672 31675 31673 31677 31670 31678 31672 31672 31675 31675
31672 31675 31676 31676 31681 31675 31681 31682 31677 31677 31677 31672 31672 31678 31672
31672 31675 31677 31678 31681 31680 31681 31673 31677 31678 31678 31673 31672 31673 31673
31672 31682 31675 31674 31672 31673 31676 31672 31678 31678 31669 31672 31671 31673 31670
31674 31674 31675 31677 31669 31680 31675 31673 31679 31672 31689 31676 31669 31675 31675
31674 31674 31670 31675 31669 31672 31675 31674 31677 31670 31668 31677 31672 31672 31672
31674 31675 31677 31677 31675 31672 31675 31673 31673 31673 31673 31675 31675 31676 31676
31672 31675 31677 31675 31673 31673 31673 31673 31679 31672 31689 31675 31675 31672 31672
31672 31681 31669 31677 31672 31672 31674 31673 31680 31679 31680 31675 31675 31673 31672
31673 31674 31676 31676 31672 31672 31673 31673 31680 31669 31673 31678 31675 31678 31678
31675 31673 31677 31676 31673 31672 31673 31673 31679 31672 31672 31675 31675 31669 31669
31673 31682 31677 31676 31669 31672 31675 31674 31680 31679 31689 31677 31675 31668 31675
31673 31675 31674 31677 31674 31672 31675 31674 31680 31678 31673 31676 31675 31676 31675
31672 31675 31676 31676 31672 31672 31673 31673 31673 31679 31672 31675 31676 31672 31672
31673 31682 31672 31677 31672 31674 31674 31672 31679 31678 31681 31677 31676 31675 31675
31673 31675 31675 31676 31672 31673 31676 31673 31680 31679 31679 31677 31674 31672 31672

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 31673 bytes 100%
1,000 31672 bytes -1 byte 100%
10,000 31671 bytes -1 byte 100%
100,000 31668 bytes -3 bytes 20.00%
1,000,000 31668 bytes 0.29%
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
31757 bytes +89 bytes (+0.28%) +2 bytes
31757 bytes +89 bytes (+0.28%) +2 bytes
31755 bytes +87 bytes (+0.27%)
31770 bytes +102 bytes (+0.32%) +15 bytes
31788 bytes +120 bytes (+0.38%) +33 bytes
31833 bytes +165 bytes (+0.52%) +78 bytes
31821 bytes +153 bytes (+0.48%) +66 bytes
31827 bytes +159 bytes (+0.50%) +72 bytes
31864 bytes +196 bytes (+0.62%) +109 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 25956 bytes -5712 bytes (-18.04%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 26601 bytes -5067 bytes (-16.00%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 28218 bytes -3450 bytes (-10.89%)
Brotli (Wikipedia) brotli brotli -q 11 29352 bytes -2316 bytes (-7.31%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 29849 bytes -1819 bytes (-5.74%)
LZMA2 (Wikipedia) xz xz -9 30536 bytes -1132 bytes (-3.57%)
ZSTD (Wikipedia) zstd zstd -19 31073 bytes -595 bytes (-1.88%)

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