Choose a version:
48% The original file has 445967 bytes (435.5k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 212144 bytes (207.2k, 48%).

After GZIP compression these minified files vary in size:
Boot
  81263 bytes (79.4k)
CDN
cdnjs
  71892 bytes (70.2k)
CDN
cdnhttps
  71638 bytes (70.0k)
CDN
gzip -6 (default)
  71281 bytes (69.6k)
local copy
gzip -9
  71045 bytes (69.4k)
local copy
libdeflate -12
  68298 bytes (66.7k)
local copy
7zip -mx=9 -tgzip
  67978 bytes (66.4k)
local copy
kzip -s0 -rn -b8
  67472 bytes (65.9k)
local copy
pigz -11 -n
  67468 bytes (65.9k)
local copy
Zopfli
  67347 bytes (65.8k)
local copy
Zopfli (defluff)
  67343 bytes (65.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-4.2.3.min.js (or via HTTPS)

You will automatically get the smallest D3 4.2.3 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 4291 bytes by using my D3 4.2.3 Zopfli version instead of the best available CDN (6.37% smaller than cdnhttps, 67347 vs. 71638 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 --mls64 --bsr18 --lazy --ohh

(found September 14, 2016)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 64  --mls64
block splitting recursion 18  --bsr18
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 4 more bytes (67343 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/v4.2.3/d3.zip --location | md5sum
3e7505605ce7b38280bcbe65b1f952a2  -
curl --silent --compressed https://minime.stephan-brumme.com/files/d3/d3-4.2.3.min.zopfli.js.gz | md5sum
3e7505605ce7b38280bcbe65b1f952a2  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v4.2.3/d3.zip --location | sha1sum
7628088c04dd40e9568b322d543250b21b37db8b  -
curl --silent --compressed https://minime.stephan-brumme.com/files/d3/d3-4.2.3.min.zopfli.js.gz | sha1sum
7628088c04dd40e9568b322d543250b21b37db8b  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 81263 bytes 3e7505605ce7b38280bcbe65b1f952a2 September 21, 2016 @ 16:50
cdnjs 71892 bytes 3e7505605ce7b38280bcbe65b1f952a2 September 13, 2016 @ 02:01
cdnhttps 71638 bytes 3e7505605ce7b38280bcbe65b1f952a2 November 22, 2016 @ 16:32

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

Other Versions

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

5.7.0, 5.6.0, 5.5.0, 5.4.0, 5.3.0, 5.2.0, 5.1.0, 5.0.1, 5.0.0,
4.13.0, 4.12.2, 4.12.1, 4.12.0, 4.11.0, 4.10.2, 4.10.1, 4.10.0,
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
67347 bytes -4 bytes zopfli --i1000000 --mls64 --bsr18 --lazy --ohh September 14, 2016 @ 03:07
67351 bytes -8 bytes zopfli --i100000 --mls64 --bsr18 --lazy --ohh September 13, 2016 @ 13:12
67359 bytes -9 bytes zopfli --i10000 --mls64 --bsr18 --lazy --ohh September 13, 2016 @ 12:09
67368 bytes -8 bytes zopfli --i1000 --mls64 --bsr18 --lazy --ohh September 13, 2016 @ 12:01
67376 bytes -2 bytes zopfli --i1000 --mls64 --bsr20 --lazy --ohh September 13, 2016 @ 12:01
67378 bytes -6 bytes zopfli --i1000 --mls64 --bsr15 --lazy --ohh September 13, 2016 @ 12:01
67384 bytes zopfli --i100 --mls64 --bsr18 --lazy --ohh September 13, 2016 @ 10:38

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

Most recent activity on November 22, 2016 @ 16:32.

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
67583 67587 67661 67654 67697 67648 67649 67662 67684 67760 67756 67881 67882 67871 67515
67547 68267 67517 68265 68270 67519 67481 67518 67431 67434 67505 67430 67468 67554 67514
67511 67522 67527 68247 68227 67510 67432 67511 67521 67476 67385 67392 67419 68237 67423
68235 67525 67500 68217 68208 67396 67502 67526 67512 67485 67472 68212 67516 68234 67493
67531 68244 68221 68220 68224 68210 67499 67511 67507 67487 67384 67481 67410 67556 67476
67511 67508 68214 67511 68214 68209 67487 67514 67494 67476 67493 67515 67408 68238 67514
68197 68205 68202 68193 68208 68207 67490 67479 67474 67500 67512 67540 67493 67533 67532
68190 67523 68192 68211 68191 68212 67491 67491 68194 67485 67486 67484 67482 67535 67428
67493 67481 67516 68223 68223 67426 68224 67510 67506 67488 67524 67482 68198 67498 67529
67490 68202 68202 67505 68215 67505 67487 67491 67490 67494 67479 68201 67482 67498 67529
67485 67485 68195 68208 68186 67493 67492 67480 67480 67494 67489 68184 67428 67488 67532
68201 68203 68200 68198 68188 67361 67479 67485 67480 67491 67476 67484 67481 67535 67539
67498 67496 68195 68185 68197 68188 67501 68191 67491 67483 67501 68208 68203 68209 67528
67482 67489 68199 68188 68201 68203 67490 67488 68195 67489 67472 68200 68205 68209 68206
67484 67485 68193 68195 68188 67347 67479 67479 67483 67481 67513 67549 67523 67572 67532
67495 67497 68196 68187 68189 68187 67491 67479 67487 67481 67476 67496 67498 68209 68196
67488 67488 68197 68189 68204 67362 67494 67480 68194 67483 68193 68185 68196 67498 67533
67495 67494 68196 68187 68188 68190 67486 67483 68184 67483 68184 68187 67501 68215 67532
68201 67487 68197 68218 68214 67377 67514 67510 68219 67484 67479 68187 67487 67526 67532
67489 67486 68197 68199 68193 68217 68185 67500 67490 67481 67480 67493 67489 68229 67532
67483 67491 67511 68216 68211 67384 68183 67505 68218 67484 68196 68199 67427 67543 67529
67487 68197 68190 68193 68200 68192 67488 67481 67486 67486 67477 68189 67520 67537 67526
67523 67486 68197 68208 68182 67510 67520 67512 67489 67480 67535 67514 67497 67551 67535

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 67384 bytes 100%
1,000 67368 bytes -16 bytes 100%
10,000 67359 bytes -9 bytes 100%
100,000 67351 bytes -8 bytes 0.87%
1,000,000 67347 bytes -4 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
67494 bytes +147 bytes (+0.22%) +22 bytes
68945 bytes +1598 bytes (+2.37%) +1473 bytes
68811 bytes +1464 bytes (+2.17%) +1339 bytes
68439 bytes +1092 bytes (+1.62%) +967 bytes
67744 bytes +397 bytes (+0.59%) +272 bytes
67638 bytes +291 bytes (+0.43%) +166 bytes
67635 bytes +288 bytes (+0.43%) +163 bytes
67493 bytes +146 bytes (+0.22%) +21 bytes
67472 bytes +125 bytes (+0.19%)

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 53344 bytes -14003 bytes (-20.79%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 59300 bytes -8047 bytes (-11.95%)
LZMA2 (Wikipedia) xz xz -9 60096 bytes -7251 bytes (-10.77%)
Brotli (Wikipedia) brotli brotli -q 11 60229 bytes -7118 bytes (-10.57%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 61583 bytes -5764 bytes (-8.56%)
Zstandard (Wikipedia) zstd zstd -19 65409 bytes -1938 bytes (-2.88%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 66778 bytes -569 bytes (-0.84%)

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