Choose a version:
47% The original file has 450758 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 213968 bytes (209.0k, 47%).

After GZIP compression these minified files vary in size:
Boot
  82277 bytes (80.3k)
CDN, direct link
cdnjs
  72833 bytes (71.1k)
CDN, direct link
gzip -6 (default)
  72350 bytes (70.7k)
local copy
jsdelivr
  72225 bytes (70.5k)
CDN, direct link
gzip -9
  72073 bytes (70.4k)
local copy
libdeflate -12
  69305 bytes (67.7k)
local copy
7zip -mx=9 -tgzip
  68981 bytes (67.4k)
local copy
kzip -s0 -rn -b7
  68692 bytes (67.1k)
local copy
pigz -11 -n
  68534 bytes (66.9k)
local copy
Zopfli
  68451 bytes (66.8k)
local copy
Zopfli (defluff)
  68450 bytes (66.8k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-4.4.2.min.js

You will automatically get the smallest D3 4.4.2 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 3774 bytes by using my D3 4.4.2 Zopfli version instead of the best available CDN (5.51% smaller than jsdelivr, 68451 vs. 72225 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 --bsr23 --lazy --ohh

(found January 21, 2017)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 64  --mls64
block splitting recursion 23  --bsr23
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 (68450 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/v4.4.2/d3.zip --location | md5sum
54e626e7e68c6a9d4eac827fe1d11902  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-4.4.2.min.zopfli.js.gz | md5sum
54e626e7e68c6a9d4eac827fe1d11902  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v4.4.2/d3.zip --location | sha1sum
6d6b2ef555595706c807217f8e44f22ca7894aac  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-4.4.2.min.zopfli.js.gz | sha1sum
6d6b2ef555595706c807217f8e44f22ca7894aac  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 82277 bytes 54e626e7e68c6a9d4eac827fe1d11902 January 21, 2017 @ 21:05
cdnjs 72833 bytes 54e626e7e68c6a9d4eac827fe1d11902 January 18, 2017 @ 12:47
jsdelivr 72225 bytes 54e626e7e68c6a9d4eac827fe1d11902 January 18, 2017 @ 11:33

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

Other Versions

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

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
68451 bytes -3 bytes zopfli --i1000000 --mls64 --bsr23 --lazy --ohh January 21, 2017 @ 19:52
68454 bytes -1 byte zopfli --i100000 --mls64 --bsr23 --lazy --ohh January 20, 2017 @ 18:14
68455 bytes -7 bytes zopfli --i100000 --mls512 --bsr7 --lazy --ohh January 20, 2017 @ 15:41
68462 bytes -10 bytes zopfli --i10000 --mls512 --bsr7 --lazy --ohh January 20, 2017 @ 14:19
68472 bytes -20 bytes zopfli --i1000 --mls512 --bsr7 --lazy --ohh January 20, 2017 @ 14:10
68492 bytes zopfli --i100 --mls512 --bsr7 --lazy --ohh January 20, 2017 @ 13:59

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 @ 15:28.

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
68750 68891 68789 68811 68775 68830 68728 68806 68746 68737 68710 68705 68684 68700 68660
68864 68498 68533 68603 68736 68692 68551 68646 68489 68642 68623 68613 68622 68649 68617
68473 68612 68609 68471 68587 68545 68631 68590 68480 68627 68612 68622 68634 68645 68622
68496 68577 68602 68868 68546 68551 68589 68500 68455 68628 68614 68624 68615 68626 68613
68611 68611 68607 68548 68546 68547 68674 68609 68632 68610 68637 68624 68625 68634 68646
68601 68605 68610 68457 68605 68547 68643 68609 68481 68608 68606 68616 68628 68630 68607
68599 68609 68609 68607 68612 69530 68660 68675 68605 68606 68609 68619 68629 68584 68618
69509 68608 69506 68607 68543 68548 68638 68605 68465 68605 68619 68617 68570 68607 68610
68518 68512 68550 68546 68632 68546 68643 68612 68465 68594 68610 68613 68593 68628 68632
68481 68524 68611 68601 68546 68547 68671 68621 68510 68603 68612 68619 68593 68633 68644
68605 68559 68604 68551 68546 68545 68640 68621 68466 68592 68608 68617 68608 68621 68636
68628 68610 68609 68598 68548 68543 68606 68604 68468 68609 68605 68628 68633 68607 68636
68569 68575 68557 68548 68551 68548 68640 68606 68466 68577 68612 68618 68565 68634 68630
68598 68606 68609 68599 68603 68680 68635 68603 68467 68572 68615 68617 68608 68604 68612
68469 68554 68534 68471 68603 68640 68637 68607 68599 68590 68612 68629 68583 68632 68613
68599 68606 68609 68602 68679 68686 68605 68619 69507 68592 68608 68617 68618 68624 68619
68597 68609 68607 68545 68602 68548 68637 68674 68598 68564 68613 68616 68563 68605 68579
68598 68608 68646 68486 68709 68703 68608 68631 68675 68562 68611 68616 68628 68590 68632
68599 68608 68613 68605 68549 68547 68651 68679 68608 68592 68617 68618 68591 68583 68616
68599 68602 68606 68606 68607 68451 68546 68469 68455 68568 68574 68616 68567 68584 68618
68599 68609 68611 68611 68612 68547 68650 68622 68467 68574 68576 68581 68568 68594 68615
68611 68604 68546 68597 68605 68608 68648 68624 68466 68589 68572 68584 68568 68586 68575
68512 68562 68562 68562 68546 68548 68457 68633 68457 68571 68563 68596 68567 68588 68621

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 68492 bytes 100%
1,000 68472 bytes -20 bytes 100%
10,000 68460 bytes -12 bytes 100%
100,000 68454 bytes -6 bytes 1.74%
1,000,000 68451 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
68707 bytes +256 bytes (+0.37%) +15 bytes
70021 bytes +1570 bytes (+2.29%) +1329 bytes
69702 bytes +1251 bytes (+1.83%) +1010 bytes
68832 bytes +381 bytes (+0.56%) +140 bytes
68707 bytes +256 bytes (+0.37%) +15 bytes
68725 bytes +274 bytes (+0.40%) +33 bytes
68737 bytes +286 bytes (+0.42%) +45 bytes
68692 bytes +241 bytes (+0.35%)
68703 bytes +252 bytes (+0.37%) +11 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 53808 bytes -14643 bytes (-21.39%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 59891 bytes -8560 bytes (-12.51%)
LZMA2 (Wikipedia) xz xz -9 60652 bytes -7799 bytes (-11.39%)
Brotli (Wikipedia) brotli brotli -q 11 60913 bytes -7538 bytes (-11.01%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 61847 bytes -6604 bytes (-9.65%)
ZSTD (Wikipedia) zstd zstd -19 66092 bytes -2359 bytes (-3.45%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 67309 bytes -1142 bytes (-1.67%)

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