Choose a version:
31% The original file has 280364 bytes (273.8k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 88145 bytes (86.1k, 31%).

After GZIP compression these minified files vary in size:
unpkg
  36493 bytes (35.6k)
CDN
cdnjs
  30908 bytes (30.2k)
CDN
gzip -6 (default)
  30739 bytes (30.0k)
local copy
gzip -9
  30658 bytes (29.9k)
local copy
7zip -mx=9 -tgzip
  29699 bytes (29.0k)
local copy
libdeflate -12
  29620 bytes (28.9k)
local copy
pigz -11 -n
  29603 bytes (28.9k)
local copy
kzip -s0 -rn -b2
  29593 bytes (28.9k)
local copy
Zopfli
  29574 bytes (28.9k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/jquery/jquery-3.4.1.min.js (or via HTTPS)

You will automatically get the smallest jQuery 3.4.1 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 1334 bytes by using my jQuery 3.4.1 Zopfli version instead of the best available CDN (4.51% smaller than cdnjs, 29574 vs. 30908 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 --mls128 --bsr4 --lazy --ohh

(found May 2, 2019)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 128  --mls128
block splitting recursion 4  --bsr4
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-3.4.1.min.js --location | md5sum
220afd743d9e9643852e31a135a9f3ae  -
curl --silent --compressed https://minime.stephan-brumme.com/files/jquery/jquery-3.4.1.min.zopfli.js.gz | md5sum
220afd743d9e9643852e31a135a9f3ae  -

SHA1:
curl --silent --compressed https://code.jquery.com/jquery-3.4.1.min.js --location | sha1sum
88523924351bac0b5d560fe0c5781e2556e7693d  -
curl --silent --compressed https://minime.stephan-brumme.com/files/jquery/jquery-3.4.1.min.zopfli.js.gz | sha1sum
88523924351bac0b5d560fe0c5781e2556e7693d  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
unpkg 36493 bytes 220afd743d9e9643852e31a135a9f3ae (invalid)
cdnjs 30908 bytes 220afd743d9e9643852e31a135a9f3ae May 1, 2019 @ 23:46

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

Other Versions

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

3.4.1, 3.4.0,
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
29574 bytes -1 byte zopfli --i100000 --mls128 --bsr4 --lazy --ohh May 2, 2019 @ 09:59
29575 bytes -1 byte zopfli --i10000 --mls8192 --bsr19 --lazy --ohh May 2, 2019 @ 08:53
29576 bytes -1 byte zopfli --i1000 --mls4096 --bsr30 --lazy --ohh May 2, 2019 @ 08:35
29577 bytes -2 bytes zopfli --i1000 --mls2048 --bsr19 --lazy --ohh May 2, 2019 @ 08:34
29579 bytes -1 byte zopfli --i1000 --mls2048 --bsr21 --lazy --ohh May 2, 2019 @ 08:34
29580 bytes zopfli --i100 --mls4096 --bsr30 --lazy --ohh May 2, 2019 @ 08:30

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

Most recent activity on May 2, 2019 @ 15:56.

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
29604 29579 29603 29576 29615 29599 29583 29583 29585 29587 29589 29584 29576 29585 29602
29600 29618 29617 29610 29611 29594 29574 29581 29591 29590 29579 29584 29595 29590 29603
29610 29588 29592 29593 29590 29589 29592 29592 29592 29591 29591 29578 29595 29588 29604
29589 29590 29590 29589 29594 29589 29590 29585 29591 29591 29591 29584 29577 29583 29603
29606 29608 29610 29587 29587 29588 29583 29584 29585 29588 29589 29584 29577 29582 29603
29600 29590 29611 29606 29590 29590 29601 29581 29592 29591 29576 29584 29592 29584 29603
29590 29590 29613 29593 29593 29592 29592 29584 29576 29591 29576 29594 29593 29584 29603
29591 29586 29594 29592 29589 29593 29591 29582 29592 29591 29576 29584 29595 29582 29603
29596 29603 29613 29607 29592 29609 29590 29592 29592 29591 29591 29584 29577 29584 29603
29588 29590 29589 29590 29590 29599 29593 29584 29592 29591 29589 29575 29594 29584 29602
29589 29585 29593 29605 29583 29588 29592 29592 29577 29591 29576 29584 29575 29583 29603
29585 29590 29615 29590 29589 29586 29593 29592 29592 29592 29578 29584 29595 29583 29603
29590 29591 29588 29593 29593 29597 29592 29583 29580 29591 29590 29575 29576 29582 29603
29591 29585 29589 29592 29589 29599 29600 29588 29577 29591 29576 29584 29595 29584 29603
29585 29584 29589 29592 29593 29595 29592 29591 29591 29591 29590 29575 29594 29585 29604
29590 29590 29591 29592 29589 29592 29595 29583 29592 29591 29576 29584 29575 29583 29603
29608 29612 29605 29607 29592 29595 29591 29592 29592 29591 29577 29575 29595 29585 29603
29588 29589 29589 29593 29593 29598 29602 29588 29579 29578 29578 29584 29595 29584 29605
29585 29590 29593 29593 29593 29592 29592 29588 29591 29591 29590 29584 29593 29584 29604
29589 29584 29589 29592 29592 29593 29591 29585 29592 29591 29591 29575 29595 29582 29604
29586 29587 29591 29589 29589 29592 29592 29592 29575 29578 29577 29576 29576 29584 29603
29590 29612 29610 29589 29594 29594 29592 29585 29578 29584 29577 29576 29575 29582 29603
29588 29590 29587 29607 29592 29591 29592 29592 29591 29591 29576 29575 29576 29585 29603

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 29580 bytes 100%
1,000 29576 bytes -4 bytes 100%
10,000 29575 bytes -1 byte 100%
100,000 29574 bytes -1 byte 3.19%
1,000,000 29574 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
29677 bytes +103 bytes (+0.35%) +84 bytes
29673 bytes +99 bytes (+0.33%) +80 bytes
29593 bytes +19 bytes (+0.06%)
29601 bytes +27 bytes (+0.09%) +8 bytes
29604 bytes +30 bytes (+0.10%) +11 bytes
29643 bytes +69 bytes (+0.23%) +50 bytes
29682 bytes +108 bytes (+0.37%) +89 bytes
29718 bytes +144 bytes (+0.49%) +125 bytes
29765 bytes +191 bytes (+0.65%) +172 bytes

Non-DEFLATE Algorithms

Archivers based on completely different compression algorithms often produce superior results.
Unfortunately, browsers only support gzip compression at the moment.
However, support for Brotli is constantly growing - but your browser doesn't support it.
Algorithm Program Parameters Size Compared To Best Zopfli
ZPAQ (Wikipedia) zpaq zpaq -method 69 24871 bytes -4703 bytes (-15.90%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 25225 bytes -4349 bytes (-14.71%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 26715 bytes -2859 bytes (-9.67%)
Brotli (Wikipedia) brotli brotli -q 11 27768 bytes -1806 bytes (-6.11%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 28398 bytes -1176 bytes (-3.98%)
LZMA2 (Wikipedia) xz xz -9 28960 bytes -614 bytes (-2.08%)
Zstandard (Wikipedia) zstd zstd -19 29236 bytes -338 bytes (-1.14%)

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 2019.
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