Choose a version:
26% The original file has 610219 bytes (595.9k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 159225 bytes (155.5k, 26%).

After GZIP compression these minified files vary in size:
Boot
  63172 bytes (61.7k)
CDN
cdnhttps
  54829 bytes (53.5k)
CDN
cdnjs
  54751 bytes (53.5k)
CDN
gzip -6 (default)
  54490 bytes (53.2k)
local copy
gzip -9
  54424 bytes (53.1k)
local copy
libdeflate -12
  51867 bytes (50.7k)
local copy
7zip -mx=9 -tgzip
  51856 bytes (50.6k)
local copy
kzip -s0 -rn -b1
  51778 bytes (50.6k)
local copy
pigz -11 -n
  51777 bytes (50.6k)
local copy
Zopfli
  51596 bytes (50.4k)
local copy
Zopfli (defluff)
  51595 bytes (50.4k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/dojo/dojo-1.8.9.min.js

You will automatically get the smallest Dojo 1.8.9 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 3155 bytes by using my Dojo 1.8.9 Zopfli version instead of the best available CDN (6.11% smaller than cdnjs, 51596 vs. 54751 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 --mls8 --bsr19 --lazy --ohh

(found December 3, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 8  --mls8
block splitting recursion 19  --bsr19
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 (51595 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed http://download.dojotoolkit.org/release-1.8.9/dojo.js --location | md5sum
ae039782e04010ee13a74af8f1493c0d  -
curl --silent --compressed http://minime.stephan-brumme.com/files/dojo/dojo-1.8.9.min.zopfli.js.gz | md5sum
ae039782e04010ee13a74af8f1493c0d  -

SHA1:
curl --silent --compressed http://download.dojotoolkit.org/release-1.8.9/dojo.js --location | sha1sum
aa175788faab4feec74ab86de854d84bf13a9888  -
curl --silent --compressed http://minime.stephan-brumme.com/files/dojo/dojo-1.8.9.min.zopfli.js.gz | sha1sum
aa175788faab4feec74ab86de854d84bf13a9888  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 63172 bytes ae039782e04010ee13a74af8f1493c0d March 19, 2015 @ 15:41
cdnjs 54751 bytes ae039782e04010ee13a74af8f1493c0d February 8, 2015 @ 14:45

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
cdnhttps 54829 bytes d3278142f9d2a38d7925a9b42b32edfa < /*
< Copyright (c) 2004-2012, 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 an optimized version of Dojo, built for deploymen [...]
< development. To get sources and documentation, please vis [...]
<
[...]
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:

1.13.0,
1.12.3, 1.12.2, 1.12.1,
1.11.5, 1.11.4, 1.11.3, 1.11.2, 1.11.1, 1.11.0,
1.10.9, 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
51596 bytes -2 bytes zopfli --i100000 --mls8 --bsr19 --lazy --ohh December 3, 2015 @ 15:52
51598 bytes -7 bytes zopfli --i100000 --mls2 --bsr21 --lazy --ohh December 3, 2015 @ 15:00
51605 bytes -2 bytes zopfli --i10000 --mls2 --bsr21 --lazy --ohh October 13, 2015 @ 19:40
51607 bytes -4 bytes zopfli --i1000 --mls2 --bsr21 --lazy --ohh September 22, 2015 @ 23:04
51611 bytes -3 bytes zopfli --i1000 --mls8 --bsr19 --lazy --ohh September 21, 2015 @ 19:20
51614 bytes -6 bytes zopfli --i1000 --mls8 --bsr15 --lazy --ohh September 19, 2015 @ 08:23
51620 bytes zopfli --i100 --mls8 --bsr15 --lazy --ohh September 18, 2015 @ 15:27

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 @ 14:36.

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 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
51684 51671 51682 51677 51680 51678 51677 51681 51683 51702 51688 51696 51705 51705 51686
51680 51632 51679 51681 51681 51678 51680 51680 51685 51672 51691 51691 51684 51683 51679
51623 51637 51632 51680 51678 51680 51683 51681 51680 51690 51682 51682 51683 51695 51682
51675 51710 51678 51678 51682 51681 51681 51682 51680 51678 51675 51684 51680 51677 51679
51617 51642 51699 51678 51679 51674 51674 51674 51682 51688 51685 51682 51683 51691 51680
51617 51630 51691 51678 51679 51680 51680 51675 51680 51693 51683 51690 51683 51685 51679
51622 51625 51680 51678 51680 51675 51681 51679 51679 51687 51685 51690 51700 51686 51680
51616 51632 51624 51677 51680 51675 51680 51675 51684 51687 51685 51683 51683 51685 51680
51618 51678 51678 51678 51679 51675 51675 51680 51696 51682 51683 51683 51683 51674 51682
51623 51634 51678 51678 51678 51679 51674 51679 51682 51682 51683 51683 51691 51683 51681
51615 51638 51679 51679 51679 51674 51674 51676 51682 51686 51684 51682 51690 51675 51679
51616 51630 51610 51676 51700 51680 51682 51685 51680 51700 51675 51691 51700 51677 51679
51624 51631 51679 51677 51678 51680 51681 51682 51699 51691 51687 51690 51704 51675 51682
51622 51635 51624 51678 51697 51679 51674 51680 51680 51683 51683 51686 51683 51673 51683
51619 51631 51623 51697 51680 51678 51683 51677 51683 51686 51688 51691 51699 51673 51683
51619 51631 51596 51675 51681 51682 51680 51675 51682 51686 51683 51683 51683 51677 51683
51616 51679 51615 51679 51680 51681 51674 51675 51680 51686 51688 51683 51699 51677 51679
51598 51633 51623 51679 51679 51675 51675 51675 51679 51686 51682 51684 51682 51704 51682
51615 51634 51620 51679 51680 51678 51682 51679 51685 51699 51692 51686 51682 51704 51680
51616 51681 51679 51678 51679 51675 51680 51682 51680 51686 51686 51684 51682 51683 51680
51618 51635 51625 51678 51679 51680 51681 51677 51679 51682 51674 51690 51687 51679 51682
51627 51625 51674 51678 51697 51674 51681 51680 51683 51675 51690 51683 51683 51681 51682
51617 51624 51622 51677 51679 51674 51674 51677 51680 51674 51674 51683 51683 51678 51679

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 51612 bytes 100%
1,000 51607 bytes -5 bytes 100%
10,000 51605 bytes -2 bytes 100%
100,000 51596 bytes -9 bytes 0.58%
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
51838 bytes +242 bytes (+0.47%) +60 bytes
51778 bytes +182 bytes (+0.35%)
51793 bytes +197 bytes (+0.38%) +15 bytes
51839 bytes +243 bytes (+0.47%) +61 bytes
51863 bytes +267 bytes (+0.52%) +85 bytes
51887 bytes +291 bytes (+0.56%) +109 bytes
51931 bytes +335 bytes (+0.65%) +153 bytes
51917 bytes +321 bytes (+0.62%) +139 bytes
51925 bytes +329 bytes (+0.64%) +147 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 37835 bytes -13761 bytes (-26.67%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 44896 bytes -6700 bytes (-12.99%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 46261 bytes -5335 bytes (-10.34%)
Brotli (Wikipedia) brotli brotli -q 11 47378 bytes -4218 bytes (-8.18%)
LZMA2 (Wikipedia) xz xz -9 48484 bytes -3112 bytes (-6.03%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 49769 bytes -1827 bytes (-3.54%)
ZSTD (Wikipedia) zstd zstd -19 49921 bytes -1675 bytes (-3.25%)

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