Choose a version:
47% The original file has 293231 bytes (286.4k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 137527 bytes (134.3k, 47%).

After GZIP compression these minified files vary in size:
Boot
  53711 bytes (52.5k)
CDN, direct link
Baidu
  46838 bytes (45.7k)
CDN, direct link
cdnjs
  46827 bytes (45.7k)
CDN, direct link
gzip -6 (default)
  46532 bytes (45.4k)
local copy
cdnhttps
  46485 bytes (45.4k)
CDN, direct link
unpkg
  46404 bytes (45.3k)
CDN, direct link
jsdelivr
  46353 bytes (45.3k)
CDN, direct link
gzip -9
  46352 bytes (45.3k)
local copy
7zip -mx=9 -tgzip
  44821 bytes (43.8k)
local copy
libdeflate -12
  44810 bytes (43.8k)
local copy
kzip -s0 -rn -b7
  44736 bytes (43.7k)
local copy
pigz -11 -n
  44655 bytes (43.6k)
local copy
Zopfli
  44538 bytes (43.5k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-3.1.6.min.js

You will automatically get the smallest D3 3.1.6 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 1815 bytes by using my D3 3.1.6 Zopfli version instead of the best available CDN (4.08% smaller than jsdelivr, 44538 vs. 46353 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 --mls64 --bsr9 --lazy --ohh

(found December 21, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 64  --mls64
block splitting recursion 9  --bsr9
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

Verify file integrity

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

MD5:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.1.6/d3.min.js --location | md5sum
e6aceeb643f7e25a7fc309498ffda6ef  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.6.min.zopfli.js.gz | md5sum
e6aceeb643f7e25a7fc309498ffda6ef  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.1.6/d3.min.js --location | sha1sum
f0ec4be38f3bf40a2f85436d5655d1fba00e3fa3  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.6.min.zopfli.js.gz | sha1sum
f0ec4be38f3bf40a2f85436d5655d1fba00e3fa3  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 53711 bytes e6aceeb643f7e25a7fc309498ffda6ef (invalid)
cdnjs 46827 bytes e6aceeb643f7e25a7fc309498ffda6ef (invalid)
cdnhttps 46485 bytes e6aceeb643f7e25a7fc309498ffda6ef December 24, 2015 @ 07:33
unpkg 46404 bytes e6aceeb643f7e25a7fc309498ffda6ef July 11, 2016 @ 16:32
jsdelivr 46353 bytes e6aceeb643f7e25a7fc309498ffda6ef (invalid)

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 46838 bytes eb8b5000a498554e50a8180418e6e5dd 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:

4.10.2, 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
44538 bytes -5 bytes zopfli --i100000 --mls64 --bsr9 --lazy --ohh December 21, 2015 @ 13:41
44543 bytes -5 bytes zopfli --i10000 --mls64 --bsr9 --lazy --ohh November 23, 2015 @ 17:27
44548 bytes -13 bytes zopfli --i1000 --mls64 --bsr9 --lazy --ohh September 20, 2015 @ 10:56
44561 bytes zopfli --i100 --mls64 --bsr9 --lazy --ohh September 18, 2015 @ 22:20

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

Most recent activity on March 3, 2017 @ 10:39.

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
44662 44725 44719 44719 44719 44719 44650 44677 44724 44714 44681 44742 44756 44740 44754
44651 44699 44603 44656 44605 44734 44610 44601 44666 44612 44590 44712 44752 44760 44747
44623 44621 44637 44625 44634 44593 44572 44573 44585 44595 44585 44586 44753 44759 44738
44611 44630 44635 44635 44706 44590 44609 44623 44575 44566 44593 44566 44752 44755 44752
44597 44614 44631 44629 44705 44597 44563 44622 44568 44574 44619 44565 44750 44759 44638
44625 44608 44713 44639 44706 44538 44594 44591 44700 44581 44594 44692 44753 44751 44737
44618 44612 44626 44621 44625 44583 44606 44589 44698 44567 44571 44565 44749 44749 44749
44617 44629 44731 44636 44717 44590 44596 44616 44557 44577 44595 44605 44757 44757 44736
44628 44639 44636 44626 44627 44607 44595 44574 44558 44568 44581 44716 44754 44746 44756
44622 44630 44630 44616 44613 44596 44600 44618 44561 44573 44561 44603 44752 44749 44740
44593 44640 44635 44622 44607 44598 44605 44592 44678 44565 44585 44665 44754 44748 44750
44598 44604 44620 44619 44619 44576 44599 44595 44573 44557 44581 44685 44748 44748 44753
44613 44615 44628 44622 44626 44587 44594 44739 44743 44563 44569 44717 44749 44750 44754
44627 44609 44625 44620 44621 44599 44608 44722 44744 44564 44585 44741 44742 44748 44749
44618 44616 44631 44614 44621 44597 44588 44602 44560 44562 44623 44567 44749 44757 44744
44612 44636 44629 44619 44623 44591 44594 44595 44574 44563 44552 44659 44744 44742 44751
44619 44631 44624 44630 44624 44601 44598 44601 44573 44564 44556 44660 44731 44748 44752
44598 44610 44633 44615 44626 44585 44596 44592 44702 44570 44561 44600 44741 44738 44749
44721 44716 44712 44717 44716 44591 44600 44619 44569 44569 44586 44579 44752 44757 44738
44628 44618 44630 44634 44705 44598 44602 44606 44566 44568 44557 44566 44747 44751 44755
44619 44618 44632 44617 44627 44591 44604 44619 44572 44567 44593 44664 44758 44757 44736
44623 44636 44631 44632 44625 44590 44604 44592 44563 44567 44588 44685 44749 44753 44738
44621 44626 44627 44626 44625 44596 44604 44619 44555 44572 44600 44666 44742 44761 44748

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 44561 bytes 100%
1,000 44548 bytes -13 bytes 100%
10,000 44543 bytes -5 bytes 100%
100,000 44538 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
44757 bytes +219 bytes (+0.49%) +21 bytes
44772 bytes +234 bytes (+0.53%) +36 bytes
44758 bytes +220 bytes (+0.49%) +22 bytes
44775 bytes +237 bytes (+0.53%) +39 bytes
44809 bytes +271 bytes (+0.61%) +73 bytes
44818 bytes +280 bytes (+0.63%) +82 bytes
44791 bytes +253 bytes (+0.57%) +55 bytes
44736 bytes +198 bytes (+0.44%)
44742 bytes +204 bytes (+0.46%) +6 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 35766 bytes -8772 bytes (-19.70%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 37850 bytes -6688 bytes (-15.02%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 38405 bytes -6133 bytes (-13.77%)
Brotli (Wikipedia) brotli brotli -q 11 40320 bytes -4218 bytes (-9.47%)
LZMA2 (Wikipedia) xz xz -9 41060 bytes -3478 bytes (-7.81%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 42855 bytes -1683 bytes (-3.78%)
ZSTD (Wikipedia) zstd zstd -19 42985 bytes -1553 bytes (-3.49%)

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