Choose a version:
47% The original file has 450736 bytes (440.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 213946 bytes (208.9k, 47%).

After GZIP compression these minified files vary in size:
Boot
  82035 bytes (80.1k)
CDN, direct link
cdnjs
  72561 bytes (70.9k)
CDN, direct link
gzip -6 (default)
  72038 bytes (70.3k)
local copy
jsdelivr
  71943 bytes (70.3k)
CDN, direct link
gzip -9
  71791 bytes (70.1k)
local copy
libdeflate -12
  68991 bytes (67.4k)
local copy
7zip -mx=9 -tgzip
  68708 bytes (67.1k)
local copy
kzip -s0 -rn -b7
  68242 bytes (66.6k)
local copy
pigz -11 -n
  68197 bytes (66.6k)
local copy
Zopfli
  68108 bytes (66.5k)
local copy
Zopfli (defluff)
  68105 bytes (66.5k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-4.4.1.min.js

You will automatically get the smallest D3 4.4.1 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 3835 bytes by using my D3 4.4.1 Zopfli version instead of the best available CDN (5.63% smaller than jsdelivr, 68108 vs. 71943 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 --mls32768 --bsr17 --lazy --ohh

(found January 10, 2017)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 32768  --mls32768
block splitting recursion 17  --bsr17
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 3 more bytes (68105 bytes).

Verify file integrity

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

MD5:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v4.4.1/d3.zip --location | md5sum
f48a2da612b6cc0080c00d755054b9ea  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-4.4.1.min.zopfli.js.gz | md5sum
f48a2da612b6cc0080c00d755054b9ea  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v4.4.1/d3.zip --location | sha1sum
1912ca6add3f8e54cd90f1e4bea9683bda7544aa  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-4.4.1.min.zopfli.js.gz | sha1sum
1912ca6add3f8e54cd90f1e4bea9683bda7544aa  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 82035 bytes f48a2da612b6cc0080c00d755054b9ea January 10, 2017 @ 05:10
cdnjs 72561 bytes f48a2da612b6cc0080c00d755054b9ea January 6, 2017 @ 18:47
jsdelivr 71943 bytes f48a2da612b6cc0080c00d755054b9ea January 6, 2017 @ 18:33

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

Other Versions

Available D3 versions at minime.stephan-brumme.com:

4.9.1, 4.9.0, 4.8.0, 4.7.4, 4.7.3, 4.7.2, 4.7.1, 4.7.0, 4.6.0, 4.5.0, 4.4.4, 4.4.3, 4.4.2, 4.4.1, 4.4.0, 4.3.0, 4.2.8, 4.2.7, 4.2.6, 4.2.5, 4.2.4, 4.2.3, 4.2.2, 4.2.1, 4.2.0, 4.1.1, 4.1.0, 4.0.0,
3.5.17, 3.5.16, 3.5.15, 3.5.14, 3.5.13, 3.5.12, 3.5.11, 3.5.10, 3.5.9, 3.5.8, 3.5.7, 3.5.6, 3.5.5, 3.5.4, 3.5.3, 3.5.2, 3.5.1, 3.5.0, 3.4.13, 3.4.12, 3.4.11, 3.4.10, 3.4.9, 3.4.8, 3.4.6, 3.4.5, 3.4.4, 3.4.3, 3.4.2, 3.4.1, 3.4.0, 3.3.13, 3.3.12, 3.3.11, 3.3.10, 3.3.9, 3.3.8, 3.3.7, 3.3.6, 3.3.5, 3.3.4, 3.3.3, 3.3.2, 3.3.1, 3.3.0, 3.2.8, 3.2.7, 3.2.6, 3.2.5, 3.2.4, 3.2.3, 3.2.2, 3.2.1, 3.2.0, 3.1.10, 3.1.9, 3.1.8, 3.1.7, 3.1.6, 3.1.5, 3.1.4, 3.1.3, 3.1.2, 3.1.1, 3.1.0, 3.0.8, 3.0.7, 3.0.6, 3.0.5, 3.0.4, 3.0.3, 3.0.2, 3.0.1, 3.0.0

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

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
68108 bytes -3 bytes zopfli --i1000000 --mls32768 --bsr17 --lazy --ohh January 10, 2017 @ 04:47
68111 bytes -2 bytes zopfli --i100000 --mls32768 --bsr17 --lazy --ohh January 9, 2017 @ 16:22
68113 bytes -11 bytes zopfli --i10000 --mls32768 --bsr17 --lazy --ohh January 9, 2017 @ 15:02
68124 bytes -13 bytes zopfli --i1000 --mls32768 --bsr17 --lazy --ohh January 9, 2017 @ 14:55
68137 bytes zopfli --i100 --mls32768 --bsr17 --lazy --ohh January 9, 2017 @ 14:50

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

Most recent activity on January 25, 2017 @ 15:30.

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
68334 68324 68430 68420 68418 68417 68413 68418 68451 68410 68427 68619 68622 68610 68440
68259 68275 68379 68158 68289 68171 68161 68174 68156 68198 68195 68204 68288 68234 68377
68267 68237 68957 68143 68962 68950 68956 68307 68282 68359 68258 68295 68296 68965 68303
68269 68300 68969 68966 68948 68270 68248 68263 68237 68240 68192 68133 68277 68960 68325
68283 68343 68252 68943 68952 68253 68943 68239 68244 68234 68254 68275 68252 68298 68282
68234 68245 68276 68940 68953 68955 68249 68254 68224 68232 68258 68245 68306 68980 68126
68942 68948 68954 68948 68948 68952 68240 68257 68242 68241 68234 68256 68212 68251 68302
68943 68233 68942 68956 68939 68294 68950 68251 68232 68223 68249 68242 68235 68252 68152
68262 68270 68244 68940 68941 68956 68263 68246 68226 68229 68252 68261 68966 68948 68288
68958 68952 68248 68940 68950 68965 68941 68232 68234 68232 68237 68240 68248 68964 68277
68943 68951 68941 68925 68941 68940 68931 68233 68227 68217 68235 68237 68240 68263 68281
68938 68944 68249 68936 68945 68948 68941 68247 68243 68233 68249 68239 68290 68951 68278
68955 68941 68950 68937 68934 68927 68229 68231 68240 68225 68229 68240 68274 68947 68280
68942 68240 68295 68946 68949 68945 68941 68245 68239 68223 68229 68240 68255 68963 68108
68247 68263 68235 68943 68951 68238 68948 68247 68242 68231 68262 68271 68270 68284 68303
68954 68254 68234 68941 68945 68940 68949 68244 68238 68234 68232 68231 68250 68962 68294
68232 68243 68242 68938 68948 68949 68952 68246 68243 68232 68239 68131 68265 68294 68283
68242 68247 68951 68946 68946 68238 68944 68263 68234 68233 68942 68938 68240 68259 68277
68246 68245 68246 68945 68946 68241 68948 68249 68239 68233 68240 68238 68250 68963 68303
68942 68948 68288 68938 68950 68934 68245 68251 68221 68231 68241 68236 68270 68961 68281
68238 68249 68956 68955 68929 68253 68927 68236 68229 68233 68940 68936 68962 68301 68283
68928 68951 68952 68936 68942 68936 68225 68236 68230 68231 68237 68272 68258 68958 68282
68258 68238 68945 68943 68942 68940 68283 68272 68226 68217 68229 68278 68302 68276 68286

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 68137 bytes 100%
1,000 68124 bytes -13 bytes 100%
10,000 68113 bytes -11 bytes 100%
100,000 68111 bytes -2 bytes 1.45%
1,000,000 68108 bytes -3 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
68243 bytes +135 bytes (+0.20%) +1 byte
69672 bytes +1564 bytes (+2.30%) +1430 bytes
69546 bytes +1438 bytes (+2.11%) +1304 bytes
69168 bytes +1060 bytes (+1.56%) +926 bytes
68472 bytes +364 bytes (+0.53%) +230 bytes
68472 bytes +364 bytes (+0.53%) +230 bytes
68379 bytes +271 bytes (+0.40%) +137 bytes
68242 bytes +134 bytes (+0.20%)
68247 bytes +139 bytes (+0.20%) +5 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 53873 bytes -14235 bytes (-20.90%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 59903 bytes -8205 bytes (-12.05%)
LZMA2 (Wikipedia) xz xz -9 60720 bytes -7388 bytes (-10.85%)
Brotli (Wikipedia) brotli brotli -q 11 60779 bytes -7329 bytes (-10.76%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 62348 bytes -5760 bytes (-8.46%)
ZSTD (Wikipedia) zstd zstd -19 66072 bytes -2036 bytes (-2.99%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 67312 bytes -796 bytes (-1.17%)

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