Choose a version:
32% The original file has 271751 bytes (265.4k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 86927 bytes (84.9k, 32%).

After GZIP compression these minified files vary in size:
Microsoft
  38892 bytes (38.0k)
CDN
cdnjs
  30544 bytes (29.8k)
CDN
Google
  30399 bytes (29.7k)
CDN
gzip -6 (default)
  30371 bytes (29.7k)
local copy
gzip -9
  30308 bytes (29.6k)
local copy
unpkg
  30289 bytes (29.6k)
CDN
7zip -mx=9 -tgzip
  29342 bytes (28.7k)
local copy
libdeflate -12
  29278 bytes (28.6k)
local copy
pigz -11 -n
  29245 bytes (28.6k)
local copy
kzip -s0 -rn -b2
  29242 bytes (28.6k)
local copy
Zopfli
  29232 bytes (28.5k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/jquery/jquery-3.3.1.min.js

You will automatically get the smallest jQuery 3.3.1 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 1057 bytes by using my jQuery 3.3.1 Zopfli version instead of the best available CDN (3.62% smaller than unpkg, 29232 vs. 30289 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 --bsr30 --lazy --ohh

(found January 22, 2018)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 2048  --mls2048
block splitting recursion 30  --bsr30
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 http://code.jquery.com/jquery-3.3.1.min.js --location | md5sum
a09e13ee94d51c524b7e2a728c7d4039  -
curl --silent --compressed http://minime.stephan-brumme.com/files/jquery/jquery-3.3.1.min.zopfli.js.gz | md5sum
a09e13ee94d51c524b7e2a728c7d4039  -

SHA1:
curl --silent --compressed http://code.jquery.com/jquery-3.3.1.min.js --location | sha1sum
0dc32db4aa9c5f03f3b38c47d883dbd4fed13aae  -
curl --silent --compressed http://minime.stephan-brumme.com/files/jquery/jquery-3.3.1.min.zopfli.js.gz | sha1sum
0dc32db4aa9c5f03f3b38c47d883dbd4fed13aae  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Microsoft 38892 bytes a09e13ee94d51c524b7e2a728c7d4039 January 22, 2018 @ 20:27
cdnjs 30544 bytes a09e13ee94d51c524b7e2a728c7d4039 January 20, 2018 @ 19:01
Google 30399 bytes a09e13ee94d51c524b7e2a728c7d4039 January 25, 2018 @ 16:33
unpkg 30289 bytes a09e13ee94d51c524b7e2a728c7d4039 January 20, 2018 @ 18:26

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
29232 bytes -1 byte zopfli --i1000000 --mls2048 --bsr30 --lazy --ohh January 22, 2018 @ 21:27
29233 bytes -2 bytes zopfli --i100000 --mls2048 --bsr30 --lazy --ohh January 22, 2018 @ 17:35
29235 bytes -1 byte zopfli --i10000 --mls1024 --bsr4 --lazy --ohh January 22, 2018 @ 17:28
29236 bytes -1 byte zopfli --i1000 --mls2048 --bsr30 --lazy --ohh January 22, 2018 @ 16:37
29237 bytes zopfli --i100 --mls512 --bsr4 --lazy --ohh January 22, 2018 @ 16:35

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

Most recent activity on January 25, 2018 @ 16:33.

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
29252 29255 29252 29241 29241 29243 29253 29240 29240 29242 29245 29245 29237 29239 29251
29254 29251 29256 29253 29253 29253 29250 29238 29233 29232 29237 29238 29237 29238 29236
29251 29257 29255 29268 29254 29257 29255 29245 29244 29239 29238 29238 29234 29246 29238
29251 29250 29252 29255 29250 29255 29255 29238 29239 29238 29238 29237 29239 29239 29239
29250 29254 29256 29272 29271 29269 29253 29238 29238 29242 29238 29238 29238 29238 29240
29253 29255 29255 29254 29254 29256 29251 29238 29234 29240 29245 29237 29237 29238 29238
29251 29252 29252 29255 29255 29265 29256 29238 29235 29238 29237 29238 29238 29240 29238
29252 29253 29252 29254 29255 29251 29250 29238 29238 29238 29238 29238 29234 29238 29238
29251 29251 29250 29254 29251 29253 29255 29237 29239 29238 29237 29238 29234 29241 29240
29252 29267 29265 29266 29255 29260 29251 29237 29239 29238 29237 29238 29238 29238 29238
29278 29255 29252 29251 29268 29255 29252 29238 29238 29238 29239 29237 29244 29240 29240
29252 29250 29252 29254 29255 29255 29252 29238 29238 29238 29238 29237 29238 29239 29237
29253 29251 29253 29251 29251 29256 29255 29238 29238 29239 29238 29238 29234 29238 29240
29252 29256 29255 29255 29254 29256 29256 29238 29237 29238 29237 29238 29234 29238 29237
29252 29251 29256 29266 29255 29255 29255 29238 29238 29238 29234 29238 29238 29238 29238
29253 29260 29254 29255 29254 29254 29251 29238 29238 29238 29232 29237 29237 29238 29237
29252 29256 29255 29255 29253 29256 29256 29238 29238 29238 29238 29238 29240 29240 29240
29252 29251 29254 29254 29254 29255 29252 29238 29238 29239 29238 29239 29245 29240 29240
29251 29252 29255 29255 29255 29256 29252 29238 29238 29239 29237 29239 29237 29241 29238
29259 29254 29253 29255 29256 29256 29243 29238 29238 29239 29238 29238 29237 29240 29238
29251 29256 29252 29256 29252 29255 29254 29238 29238 29238 29238 29238 29237 29238 29240
29251 29256 29256 29253 29250 29256 29251 29238 29238 29239 29232 29238 29245 29240 29238
29250 29260 29255 29253 29253 29253 29252 29238 29238 29238 29245 29239 29239 29238 29238

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 29237 bytes 100%
1,000 29236 bytes -1 byte 100%
10,000 29235 bytes -1 byte 100%
100,000 29232 bytes -3 bytes 3.77%
1,000,000 29232 bytes 0.87%
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
29323 bytes +91 bytes (+0.31%) +81 bytes
29321 bytes +89 bytes (+0.30%) +79 bytes
29242 bytes +10 bytes (+0.03%)
29254 bytes +22 bytes (+0.08%) +12 bytes
29260 bytes +28 bytes (+0.10%) +18 bytes
29286 bytes +54 bytes (+0.18%) +44 bytes
29323 bytes +91 bytes (+0.31%) +81 bytes
29359 bytes +127 bytes (+0.43%) +117 bytes
29399 bytes +167 bytes (+0.57%) +157 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 24547 bytes -4685 bytes (-16.03%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 24911 bytes -4321 bytes (-14.78%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 26361 bytes -2871 bytes (-9.82%)
Brotli (Wikipedia) brotli brotli -q 11 27480 bytes -1752 bytes (-5.99%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 27960 bytes -1272 bytes (-4.35%)
LZMA2 (Wikipedia) xz xz -9 28604 bytes -628 bytes (-2.15%)
ZSTD (Wikipedia) zstd zstd -19 29007 bytes -225 bytes (-0.77%)

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