Choose a version:
47% The original file has 268046 bytes (261.8k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 126854 bytes (123.9k, 47%).

After GZIP compression these minified files vary in size:
Boot
  48730 bytes (47.6k)
CDN, direct link
Baidu
  42640 bytes (41.6k)
CDN, direct link
cdnjs
  42634 bytes (41.6k)
CDN, direct link
gzip -6 (default)
  42302 bytes (41.3k)
local copy
cdnhttps
  42286 bytes (41.3k)
CDN, direct link
unpkg
  42275 bytes (41.3k)
CDN, direct link
gzip -9
  42186 bytes (41.2k)
local copy
7zip -mx=9 -tgzip
  40795 bytes (39.8k)
local copy
libdeflate -12
  40758 bytes (39.8k)
local copy
pigz -11 -n
  40728 bytes (39.8k)
local copy
kzip -s0 -rn -b8
  40647 bytes (39.7k)
local copy
Zopfli
  40500 bytes (39.6k)
local copy
Zopfli (defluff)
  40499 bytes (39.5k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-3.0.2.min.js

You will automatically get the smallest D3 3.0.2 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 1775 bytes by using my D3 3.0.2 Zopfli version instead of the best available CDN (4.38% smaller than unpkg, 40500 vs. 42275 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 --mls2048 --bsr14 --lazy --ohh

(found November 23, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 2048  --mls2048
block splitting recursion 14  --bsr14
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 (40499 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/v3.0.2/d3.min.js --location | md5sum
902138926b2ec42418ab8f8c79f73018  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.0.2.min.zopfli.js.gz | md5sum
902138926b2ec42418ab8f8c79f73018  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.0.2/d3.min.js --location | sha1sum
efdccd4c66ccf57d920be03aad09a333a3f286d6  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.0.2.min.zopfli.js.gz | sha1sum
efdccd4c66ccf57d920be03aad09a333a3f286d6  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 48730 bytes 902138926b2ec42418ab8f8c79f73018 (invalid)
cdnjs 42634 bytes 902138926b2ec42418ab8f8c79f73018 (invalid)
cdnhttps 42286 bytes 902138926b2ec42418ab8f8c79f73018 December 24, 2015 @ 07:33
unpkg 42275 bytes 902138926b2ec42418ab8f8c79f73018 July 11, 2016 @ 16:32

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 42640 bytes f97d80e59be3363154beb098121fa7d9 only whitespaces differ (invalid)

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
40500 bytes -5 bytes zopfli --i100000 --mls2048 --bsr14 --lazy --ohh November 23, 2015 @ 16:59
40505 bytes -5 bytes zopfli --i10000 --mls2048 --bsr14 --lazy --ohh November 23, 2015 @ 15:59
40510 bytes -9 bytes zopfli --i1000 --mls2048 --bsr14 --lazy --ohh September 20, 2015 @ 21:13
40519 bytes -2 bytes zopfli --i1000 --mls2048 --bsr11 --lazy --ohh September 20, 2015 @ 21:10
40521 bytes -5 bytes zopfli --i1000 --mls512 --bsr6 --lazy --ohh September 20, 2015 @ 20:58
40526 bytes zopfli --i100 --mls2048 --bsr14 --lazy --ohh September 18, 2015 @ 21:19

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

Most recent activity on March 5, 2017 @ 03:23.

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
40630 40625 40632 40697 40631 40631 40640 40693 40645 40719 40720 40643 40718 40716 40727
40695 40605 40699 40700 40692 40696 40706 40683 40700 40721 40523 40548 40723 40635 40704
40566 40688 40695 40556 40570 40532 40690 40695 40519 40719 40715 40712 40719 40593 40727
40614 40609 40687 40538 40691 40695 40578 40583 40563 40545 40682 40585 40720 40575 40718
40546 40580 40613 40699 40556 40597 40564 40696 40576 40535 40585 40611 40718 40562 40706
40685 40689 40556 40543 40684 40579 40559 40693 40602 40712 40577 40709 40716 40564 40716
40537 40556 40545 40550 40698 40579 40585 40565 40566 40572 40575 40568 40719 40577 40718
40566 40513 40561 40560 40601 40546 40572 40701 40701 40719 40517 40631 40718 40626 40598
40574 40538 40559 40534 40700 40554 40562 40579 40561 40719 40527 40580 40718 40624 40600
40573 40565 40696 40557 40558 40561 40604 40574 40589 40719 40719 40713 40721 40581 40720
40567 40520 40561 40534 40697 40523 40598 40571 40561 40522 40500 40583 40721 40622 40724
40560 40629 40593 40583 40562 40578 40586 40583 40597 40721 40572 40540 40705 40590 40732
40699 40589 40593 40561 40527 40555 40591 40578 40698 40532 40518 40576 40734 40624 40716
40574 40548 40564 40565 40549 40562 40691 40581 40686 40705 40591 40580 40720 40589 40716
40577 40602 40627 40556 40546 40571 40577 40595 40579 40588 40571 40578 40587 40624 40717
40579 40553 40701 40571 40516 40524 40584 40582 40573 40706 40516 40589 40703 40716 40716
40576 40631 40695 40564 40577 40554 40573 40688 40603 40719 40719 40589 40720 40612 40603
40567 40591 40696 40581 40517 40520 40637 40581 40586 40545 40574 40572 40720 40613 40716
40575 40577 40632 40556 40698 40549 40558 40584 40571 40719 40719 40584 40721 40634 40718
40570 40535 40683 40561 40694 40551 40569 40573 40570 40721 40583 40598 40702 40614 40716
40569 40553 40563 40531 40559 40537 40537 40692 40564 40719 40719 40598 40715 40624 40714
40571 40587 40595 40601 40585 40589 40577 40587 40583 40586 40585 40582 40718 40624 40716
40567 40557 40696 40559 40696 40587 40599 40580 40558 40720 40714 40584 40715 40619 40596

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 40526 bytes 100%
1,000 40510 bytes -16 bytes 100%
10,000 40505 bytes -5 bytes 100%
100,000 40500 bytes -5 bytes 0.29%
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
40737 bytes +237 bytes (+0.59%) +90 bytes
40742 bytes +242 bytes (+0.60%) +95 bytes
40739 bytes +239 bytes (+0.59%) +92 bytes
40752 bytes +252 bytes (+0.62%) +105 bytes
40751 bytes +251 bytes (+0.62%) +104 bytes
40771 bytes +271 bytes (+0.67%) +124 bytes
40760 bytes +260 bytes (+0.64%) +113 bytes
40747 bytes +247 bytes (+0.61%) +100 bytes
40647 bytes +147 bytes (+0.36%)

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 32812 bytes -7688 bytes (-18.98%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 34622 bytes -5878 bytes (-14.51%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 36076 bytes -4424 bytes (-10.92%)
Brotli (Wikipedia) brotli brotli -q 11 36855 bytes -3645 bytes (-9.00%)
LZMA2 (Wikipedia) xz xz -9 37632 bytes -2868 bytes (-7.08%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 39208 bytes -1292 bytes (-3.19%)
ZSTD (Wikipedia) zstd zstd -19 39283 bytes -1217 bytes (-3.00%)

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