Choose a version:
47% The original file has 293228 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 137486 bytes (134.3k, 47%).

After GZIP compression these minified files vary in size:
Boot
  53556 bytes (52.3k)
CDN, direct link
Baidu
  46727 bytes (45.6k)
CDN, direct link
cdnjs
  46715 bytes (45.6k)
CDN, direct link
gzip -6 (default)
  46426 bytes (45.3k)
local copy
cdnhttps
  46382 bytes (45.3k)
CDN, direct link
unpkg
  46295 bytes (45.2k)
CDN, direct link
gzip -9
  46240 bytes (45.2k)
local copy
7zip -mx=9 -tgzip
  44720 bytes (43.7k)
local copy
libdeflate -12
  44712 bytes (43.7k)
local copy
kzip -s0 -rn -b7
  44644 bytes (43.6k)
local copy
pigz -11 -n
  44491 bytes (43.4k)
local copy
Zopfli
  44434 bytes (43.4k)
local copy
Zopfli (defluff)
  44431 bytes (43.4k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-3.1.4.min.js

You will automatically get the smallest D3 3.1.4 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 1861 bytes by using my D3 3.1.4 Zopfli version instead of the best available CDN (4.19% smaller than unpkg, 44434 vs. 46295 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 --mls512 --bsr13 --lazy --ohh

(found December 21, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 512  --mls512
block splitting recursion 13  --bsr13
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 3 more bytes (44431 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/v3.1.4/d3.min.js --location | md5sum
f7fd295d6f9d956d87d9c91517aa6458  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.4.min.zopfli.js.gz | md5sum
f7fd295d6f9d956d87d9c91517aa6458  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.1.4/d3.min.js --location | sha1sum
2c808eb66801563cc8c613ef8e2ec1ed830a1c56  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.4.min.zopfli.js.gz | sha1sum
2c808eb66801563cc8c613ef8e2ec1ed830a1c56  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 53556 bytes f7fd295d6f9d956d87d9c91517aa6458 (invalid)
cdnjs 46715 bytes f7fd295d6f9d956d87d9c91517aa6458 (invalid)
cdnhttps 46382 bytes f7fd295d6f9d956d87d9c91517aa6458 December 24, 2015 @ 07:33
unpkg 46295 bytes f7fd295d6f9d956d87d9c91517aa6458 July 11, 2016 @ 16:32

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 46727 bytes a1685e633475d59210f845e9cea7bf8f 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
44434 bytes -8 bytes zopfli --i100000 --mls512 --bsr13 --lazy --ohh December 21, 2015 @ 13:37
44442 bytes -3 bytes zopfli --i10000 --mls512 --bsr13 --lazy --ohh November 23, 2015 @ 17:17
44445 bytes -4 bytes zopfli --i1000 --mls512 --bsr13 --lazy --ohh September 20, 2015 @ 12:50
44449 bytes -2 bytes zopfli --i1000 --mls1024 --bsr11 --lazy --ohh September 20, 2015 @ 12:45
44451 bytes zopfli --i100 --mls512 --bsr13 --lazy --ohh September 18, 2015 @ 20:33

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 @ 09:26.

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
44628 44618 44620 44619 44620 44621 44549 44638 44612 44609 44621 44639 44633 44627 44631
44541 44600 44507 44594 44614 44500 44558 44590 44644 44627 44522 44601 44629 44524 44606
44500 44470 44536 44547 44546 44526 44509 44471 44467 44461 44502 44451 44629 44640 44623
44617 44481 44619 44604 44504 44514 44478 44537 44494 44446 44470 44460 44623 44609 44628
44490 44510 44563 44601 44496 44511 44502 44518 44499 44455 44514 44528 44623 44642 44507
44508 44490 44516 44605 44609 44498 44489 44526 44574 44627 44469 44582 44630 44639 44637
44485 44478 44615 44522 44528 44519 44499 44598 44593 44445 44465 44490 44628 44638 44608
44518 44479 44611 44515 44535 44497 44480 44519 44446 44444 44475 44521 44630 44626 44622
44620 44494 44564 44510 44534 44503 44499 44517 44471 44444 44467 44563 44633 44640 44622
44503 44481 44614 44505 44529 44495 44485 44528 44434 44448 44464 44469 44622 44644 44621
44476 44501 44544 44516 44536 44497 44497 44510 44593 44445 44515 44561 44643 44639 44622
44622 44478 44542 44517 44531 44507 44497 44579 44580 44446 44471 44579 44633 44531 44599
44497 44523 44613 44512 44514 44506 44498 44517 44634 44444 44469 44623 44628 44638 44638
44483 44483 44618 44603 44533 44505 44496 44519 44470 44457 44463 44624 44641 44643 44624
44478 44476 44509 44515 44530 44563 44500 44485 44500 44440 44464 44487 44634 44531 44495
44492 44549 44614 44503 44533 44500 44496 44509 44451 44446 44467 44557 44630 44638 44624
44501 44505 44516 44516 44531 44506 44500 44513 44590 44448 44462 44564 44624 44626 44599
44482 44484 44519 44510 44527 44527 44503 44586 44582 44447 44489 44461 44632 44508 44632
44627 44487 44615 44519 44533 44523 44502 44528 44454 44447 44502 44506 44641 44641 44639
44487 44484 44553 44598 44529 44494 44499 44520 44453 44445 44529 44468 44641 44640 44639
44482 44479 44535 44509 44532 44509 44499 44578 44592 44444 44466 44579 44634 44641 44632
44506 44481 44611 44530 44531 44504 44496 44511 44593 44447 44467 44586 44642 44618 44632
44484 44470 44534 44605 44521 44521 44499 44586 44468 44447 44466 44567 44629 44638 44623

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 44451 bytes 100%
1,000 44445 bytes -6 bytes 100%
10,000 44442 bytes -3 bytes 100%
100,000 44434 bytes -8 bytes 0.58%
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
44656 bytes +222 bytes (+0.50%) +12 bytes
44661 bytes +227 bytes (+0.51%) +17 bytes
44661 bytes +227 bytes (+0.51%) +17 bytes
44671 bytes +237 bytes (+0.53%) +27 bytes
44704 bytes +270 bytes (+0.61%) +60 bytes
44723 bytes +289 bytes (+0.65%) +79 bytes
44697 bytes +263 bytes (+0.59%) +53 bytes
44644 bytes +210 bytes (+0.47%)
44649 bytes +215 bytes (+0.48%) +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 35661 bytes -8773 bytes (-19.74%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 37771 bytes -6663 bytes (-15.00%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 38325 bytes -6109 bytes (-13.75%)
Brotli (Wikipedia) brotli brotli -q 11 40277 bytes -4157 bytes (-9.36%)
LZMA2 (Wikipedia) xz xz -9 40980 bytes -3454 bytes (-7.77%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 42751 bytes -1683 bytes (-3.79%)
ZSTD (Wikipedia) zstd zstd -19 42903 bytes -1531 bytes (-3.45%)

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