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
  68695 bytes (67.1k)
local copy
pigz -11 -n
  68536 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/d3-4.4.3.min.js

You will automatically get the smallest D3 4.4.3 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 3774 bytes by using my D3 4.4.3 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 27, 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/v4.4.3/d3.zip --location | md5sum
a54f2848d77b9af73df73f79e1f6a87d  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-4.4.3.min.zopfli.js.gz | md5sum
a54f2848d77b9af73df73f79e1f6a87d  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v4.4.3/d3.zip --location | sha1sum
17284e8f8fdfd48ddfd4e16eb036033465b27ef0  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-4.4.3.min.zopfli.js.gz | sha1sum
17284e8f8fdfd48ddfd4e16eb036033465b27ef0  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 82277 bytes a54f2848d77b9af73df73f79e1f6a87d January 21, 2017 @ 21:05
cdnjs 72833 bytes a54f2848d77b9af73df73f79e1f6a87d January 21, 2017 @ 00:32
jsdelivr 72225 bytes a54f2848d77b9af73df73f79e1f6a87d January 21, 2017 @ 00:34

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
68451 bytes -1 byte zopfli --i1000000 --mls64 --bsr23 --lazy --ohh January 27, 2017 @ 00:22
68452 bytes -3 bytes zopfli --i1000000 --mls512 --bsr23 --lazy --ohh January 27, 2017 @ 00:22
68455 bytes -6 bytes zopfli --i100000 --mls512 --bsr23 --lazy --ohh January 25, 2017 @ 14:31
68461 bytes -12 bytes zopfli --i10000 --mls512 --bsr40 --lazy --ohh January 25, 2017 @ 12:47
68473 bytes -10 bytes zopfli --i1000 --mls512 --bsr40 --lazy --ohh January 25, 2017 @ 12:22
68483 bytes -13 bytes zopfli --i1000 --mls16 --bsr6 --lazy --ohh January 25, 2017 @ 12:22
68496 bytes zopfli --i100 --mls16 --bsr6 --lazy --ohh January 25, 2017 @ 11:55

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

Most recent activity on January 27, 2017 @ 10:04.

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
68751 68891 68789 68811 68775 68829 68727 68806 68746 68738 68714 68706 68684 68701 68660
68864 68498 68532 68604 68736 68692 68551 68646 68490 68642 68623 68613 68623 68649 68617
68473 68612 68609 68471 68587 68545 68630 68590 68479 68627 68612 68622 68634 68644 68629
68493 68577 68602 68868 68546 68551 68589 68500 68470 68628 68612 68623 68615 68625 68611
68611 68611 68607 68548 68547 68547 68674 68609 68632 68616 68637 68624 68626 68634 68646
68601 68604 68611 68457 68606 68547 68645 68611 68464 68608 68607 68616 68609 68630 68607
68600 68609 68609 68607 69524 69530 68660 68676 68605 68605 68609 68617 68630 68583 68617
69509 68608 69505 68607 68543 68548 68642 68609 68474 68610 68615 68616 68571 68607 68609
68518 68514 68551 68546 68633 68546 68643 68611 68465 68594 68609 68613 68592 68628 68632
68476 68526 68610 68600 68546 68548 68671 68621 68510 68603 68620 68618 68571 68633 68644
68605 68560 68605 68552 68546 68545 68640 68621 68466 68593 68608 68617 68608 68621 68636
68628 68611 68609 68599 68548 68543 68606 68604 68468 68609 68606 68628 68633 68606 68636
68569 68575 68557 68549 68551 68548 68642 68606 68466 68580 68612 68618 68603 68631 68631
68599 68606 68608 68601 68604 68681 68636 68605 68467 68630 68614 68615 68608 68611 68610
68470 68555 68531 68471 68603 68640 68638 68607 68600 68590 68612 68629 68577 68633 68617
68599 68606 68609 68602 68678 68686 68604 68620 69507 68568 68609 68617 68618 68638 68621
68597 68609 68608 68546 68602 68548 68638 68674 68599 68563 68613 68616 68563 68605 68580
68598 68608 68646 68486 68709 68709 68608 68618 68676 68562 68612 68615 68629 68590 68631
68599 68608 68613 68605 68549 68547 68651 68679 68609 68592 68617 68618 68590 68583 68617
68599 68603 68606 68606 68607 68451 68546 68469 68452 68568 68575 68617 68567 68584 68620
68598 68610 68611 68611 68612 68547 68650 68622 68466 68575 68576 68581 68568 68590 68614
68611 68604 68546 68598 68605 68609 68648 68624 68465 68589 68572 68584 68565 68585 68574
68512 68562 68563 68562 68546 68548 68457 68634 68457 68593 68563 68596 68566 68586 68622

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 68496 bytes 100%
1,000 68473 bytes -23 bytes 100%
10,000 68461 bytes -12 bytes 100%
100,000 68455 bytes -6 bytes 1.74%
1,000,000 68451 bytes -4 bytes 0.58%
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
68710 bytes +259 bytes (+0.38%) +15 bytes
70017 bytes +1566 bytes (+2.29%) +1322 bytes
69700 bytes +1249 bytes (+1.82%) +1005 bytes
68832 bytes +381 bytes (+0.56%) +137 bytes
68707 bytes +256 bytes (+0.37%) +12 bytes
68721 bytes +270 bytes (+0.39%) +26 bytes
68738 bytes +287 bytes (+0.42%) +43 bytes
68695 bytes +244 bytes (+0.36%)
68700 bytes +249 bytes (+0.36%) +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 53809 bytes -14642 bytes (-21.39%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 59897 bytes -8554 bytes (-12.50%)
LZMA2 (Wikipedia) xz xz -9 60656 bytes -7795 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 67323 bytes -1128 bytes (-1.65%)

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