Choose a version:
24% The original file has 375088 bytes (366.3k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 89269 bytes (87.2k, 24%).

After GZIP compression these minified files vary in size:
Boot
  35017 bytes (34.2k)
CDN, direct link
cdnhttps
  30550 bytes (29.8k)
CDN, direct link
cdnjs
  30522 bytes (29.8k)
CDN, direct link
gzip -6 (default)
  30422 bytes (29.7k)
local copy
gzip -9
  30385 bytes (29.7k)
local copy
libdeflate -12
  29065 bytes (28.4k)
local copy
7zip -mx=9 -tgzip
  29024 bytes (28.3k)
local copy
kzip -s0 -rn -b1
  29008 bytes (28.3k)
local copy
pigz -11 -n
  28954 bytes (28.3k)
local copy
Zopfli
  28871 bytes (28.2k)
local copy
Zopfli (defluff)
  28870 bytes (28.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/dojo/dojo-1.4.2.min.js

You will automatically get the smallest Dojo 1.4.2 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 1651 bytes by using my Dojo 1.4.2 Zopfli version instead of the best available CDN (5.72% smaller than cdnjs, 28871 vs. 30522 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 --mls64 --bsr30 --lazy --ohh

(found December 1, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 64  --mls64
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

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 (28870 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed http://download.dojotoolkit.org/release-1.4.2/dojo.js --location | md5sum
5c9bd713ac3ad48b1268679eb9b537a8  -
curl --silent --compressed http://minime.stephan-brumme.com/files/dojo/dojo-1.4.2.min.zopfli.js.gz | md5sum
5c9bd713ac3ad48b1268679eb9b537a8  -

SHA1:
curl --silent --compressed http://download.dojotoolkit.org/release-1.4.2/dojo.js --location | sha1sum
813d3e6c3bd6cf78010da4f778903d1dbb20f08e  -
curl --silent --compressed http://minime.stephan-brumme.com/files/dojo/dojo-1.4.2.min.zopfli.js.gz | sha1sum
813d3e6c3bd6cf78010da4f778903d1dbb20f08e  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 35017 bytes 5c9bd713ac3ad48b1268679eb9b537a8 March 19, 2015 @ 15:31
cdnjs 30522 bytes 5c9bd713ac3ad48b1268679eb9b537a8 February 8, 2015 @ 14:45

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
cdnhttps 30550 bytes 0de3f02c356d9322d602d8dc20b93eab < /*
< Copyright (c) 2004-2009, The Dojo Foundation All Rights R [...]
< Available via Academic Free License >= 2.1 OR the modifie [...]
< see: http://dojotoolkit.org/license for details
< */
<
< /*
< This is a compiled version of Dojo, built for deployment [...]
< development. To get an editable version, please visit:
<
[...]
December 24, 2015 @ 07:33

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

Other Versions

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

1.12.2, 1.12.1,
1.11.4, 1.11.3, 1.11.2, 1.11.1, 1.11.0,
1.10.8, 1.10.7, 1.10.6, 1.10.5, 1.10.4, 1.10.3, 1.10.2, 1.10.1, 1.10.0,
1.9.11, 1.9.10, 1.9.9, 1.9.8, 1.9.7, 1.9.6, 1.9.5, 1.9.4, 1.9.3, 1.9.2, 1.9.1, 1.9.0,
1.8.12, 1.8.11, 1.8.10, 1.8.9, 1.8.8, 1.8.7, 1.8.6, 1.8.5, 1.8.4, 1.8.3, 1.8.2, 1.8.1, 1.8.0,
1.7.10, 1.7.9, 1.7.8, 1.7.7, 1.7.6, 1.7.5, 1.7.4, 1.7.3, 1.7.2, 1.7.1, 1.7.0,
1.6.3, 1.6.2, 1.6.1, 1.6.0,
1.5.4, 1.5.3, 1.5.2, 1.5.1, 1.5.0,
1.4.6, 1.4.5, 1.4.4, 1.4.3, 1.4.2, 1.4.1, 1.4.0,
1.3.3, 1.3.2, 1.3.1, 1.3.0,
1.2.3

The project site contains an overview how well these versions were compressed.
Other interesting projects are AngularJS, BackboneJS, Bootstrap, D3, Ember, jQuery, Knockout, lodash, React, Socket.IO, ThreeJS, UnderscoreJS and Vue.

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
28871 bytes -3 bytes zopfli --i100000 --mls64 --bsr30 --lazy --ohh December 1, 2015 @ 15:15
28874 bytes -4 bytes zopfli --i10000 --mls64 --bsr30 --lazy --ohh November 22, 2015 @ 22:11
28878 bytes -8 bytes zopfli --i1000 --mls64 --bsr30 --lazy --ohh September 24, 2015 @ 11:50
28886 bytes zopfli --i100 --mls64 --bsr30 --lazy --ohh September 24, 2015 @ 11:46

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
28943 28939 28952 28948 28944 28968 28954 28960 28959 28961 28958 28952 28971 28954 28957
28925 28951 28941 28948 28923 28914 28917 28927 28933 28953 28924 28960 28957 28960 28952
28921 28923 28917 28924 28924 28917 28935 28943 28940 28959 28935 28961 28903 28959 28959
28924 28929 28934 28931 28946 28924 28919 28919 28939 28948 28936 28962 28957 28959 28957
28921 28923 28918 28929 28924 28923 28929 28932 28932 28926 28926 28951 28958 28958 28955
28934 28926 28922 28918 28912 28920 28916 28914 28944 28960 28925 28953 28942 28952 28953
28926 28924 28923 28924 28920 28918 28918 28922 28940 28953 28936 28914 28953 28961 28950
28927 28918 28915 28910 28940 28919 28921 28918 28922 28952 28933 28952 28957 28969 28960
28919 28918 28920 28929 28920 28912 28910 28921 28928 28910 28916 28896 28957 28951 28956
28917 28912 28918 28918 28909 28916 28920 28924 28927 28914 28913 28896 28929 28953 28952
28909 28911 28907 28912 28909 28917 28916 28923 28925 28954 28915 28954 28902 28958 28957
28905 28916 28942 28914 28910 28910 28922 28922 28922 28916 28908 28960 28959 28958 28964
28912 28917 28908 28913 28923 28907 28915 28909 28925 28916 28932 28950 28947 28957 28957
28913 28929 28911 28932 28925 28917 28915 28928 28934 28915 28919 28951 28959 28958 28957
28917 28901 28898 28921 28911 28919 28921 28913 28934 28924 28915 28953 28903 28961 28961
28919 28917 28937 28920 28913 28921 28927 28932 28920 28923 28950 28957 28959 28952 28952
28897 28898 28892 28910 28900 28920 28920 28931 28911 28914 28926 28955 28959 28961 28956
28918 28925 28930 28921 28925 28902 28951 28911 28929 28917 28938 28955 28940 28959 28951
28897 28897 28932 28911 28917 28922 28927 28931 28929 28961 28921 28960 28943 28956 28951
28928 28910 28911 28909 28910 28915 28922 28912 28915 28912 28960 28960 28900 28958 28951
28909 28911 28929 28914 28930 28910 28918 28922 28920 28908 28916 28920 28902 28959 28958
28928 28920 28913 28909 28910 28871 28915 28935 28926 28917 28913 28951 28897 28965 28952
28912 28908 28916 28914 28915 28915 28920 28923 28929 28914 28909 28953 28968 28952 28952

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 28886 bytes 100%
1,000 28878 bytes -8 bytes 100%
10,000 28874 bytes -4 bytes 100%
100,000 28871 bytes -3 bytes 0.29%
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
29013 bytes +142 bytes (+0.49%) +5 bytes
29008 bytes +137 bytes (+0.47%)
29049 bytes +178 bytes (+0.62%) +41 bytes
29021 bytes +150 bytes (+0.52%) +13 bytes
29043 bytes +172 bytes (+0.60%) +35 bytes
29031 bytes +160 bytes (+0.55%) +23 bytes
29025 bytes +154 bytes (+0.53%) +17 bytes
29035 bytes +164 bytes (+0.57%) +27 bytes
29077 bytes +206 bytes (+0.71%) +69 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 22987 bytes -5884 bytes (-20.38%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 25768 bytes -3103 bytes (-10.75%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 26626 bytes -2245 bytes (-7.78%)
Brotli (Wikipedia) brotli brotli -q 11 26823 bytes -2048 bytes (-7.09%)
LZMA2 (Wikipedia) xz xz -9 27724 bytes -1147 bytes (-3.97%)
ZSTD (Wikipedia) zstd zstd -19 28470 bytes -401 bytes (-1.39%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 28597 bytes -274 bytes (-0.95%)

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