Choose a version:
45% The original file has 337839 bytes (329.9k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 151701 bytes (148.1k, 45%).

After GZIP compression these minified files vary in size:
Boot
  61048 bytes (59.6k)
CDN, direct link
cdnhttps
  53641 bytes (52.4k)
CDN, direct link
cdnjs
  53641 bytes (52.4k)
CDN, direct link
jsdelivr
  53641 bytes (52.4k)
CDN, direct link
unpkg
  53641 bytes (52.4k)
CDN, direct link
gzip -6 (default)
  53516 bytes (52.3k)
local copy
gzip -9
  53376 bytes (52.1k)
local copy
libdeflate -12
  51679 bytes (50.5k)
local copy
7zip -mx=9 -tgzip
  51620 bytes (50.4k)
local copy
pigz -11 -n
  51345 bytes (50.1k)
local copy
kzip -s0 -rn -b8
  51336 bytes (50.1k)
local copy
Zopfli
  51276 bytes (50.1k)
local copy
Zopfli (defluff)
  51274 bytes (50.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-3.5.14.min.js

You will automatically get the smallest D3 3.5.14 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 2365 bytes by using my D3 3.5.14 Zopfli version instead of the best available CDN (4.61% smaller than unpkg, 51276 vs. 53641 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 --mls1024 --bsr16 --lazy --ohh

(found January 28, 2016)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 1024  --mls1024
block splitting recursion 16  --bsr16
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 2 more bytes (51274 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/v3.5.14/d3.min.js --location | md5sum
7f11dc3a5c3c0ebfa339e251db28c033  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.5.14.min.zopfli.js.gz | md5sum
7f11dc3a5c3c0ebfa339e251db28c033  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.5.14/d3.min.js --location | sha1sum
97019d31fc9c84074b5e988ec53c32916e610532  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.5.14.min.zopfli.js.gz | sha1sum
97019d31fc9c84074b5e988ec53c32916e610532  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 61048 bytes 7f11dc3a5c3c0ebfa339e251db28c033 January 29, 2016 @ 12:37
cdnhttps 53641 bytes 7f11dc3a5c3c0ebfa339e251db28c033 November 22, 2016 @ 16:32
cdnjs 53641 bytes 7f11dc3a5c3c0ebfa339e251db28c033 (invalid)
jsdelivr 53641 bytes 7f11dc3a5c3c0ebfa339e251db28c033 (invalid)
unpkg 53641 bytes 7f11dc3a5c3c0ebfa339e251db28c033 July 11, 2016 @ 16:30

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
51276 bytes -3 bytes zopfli --i1000000 --mls1024 --bsr16 --lazy --ohh January 28, 2016 @ 21:18
51279 bytes -3 bytes zopfli --i100000 --mls1024 --bsr16 --lazy --ohh January 28, 2016 @ 13:03
51282 bytes -4 bytes zopfli --i10000 --mls1024 --bsr16 --lazy --ohh January 28, 2016 @ 11:41
51286 bytes -11 bytes zopfli --i1000 --mls1024 --bsr16 --lazy --ohh January 28, 2016 @ 11:26
51297 bytes -7 bytes zopfli --i1000 --mls32768 --bsr9 --lazy --ohh January 28, 2016 @ 11:22
51304 bytes zopfli --i100 --mls32768 --bsr9 --lazy --ohh January 28, 2016 @ 11:12

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

Most recent activity on November 22, 2016 @ 16:32.

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
51456 51457 51458 51422 51466 51466 51464 51455 51451 51453 51538 51538 51426 51438 51562
51358 51340 51332 51325 51367 51328 51386 51412 51419 51406 51412 51558 51407 51403 51304
51341 51283 51475 51389 51362 51409 51362 51425 51418 51403 51398 51414 51403 51420 51313
51364 51325 51370 51358 51461 51419 51378 51394 51399 51434 51391 51469 51430 51402 51298
51328 51443 51443 51386 51405 51430 51363 51410 51411 51405 51395 51424 51551 51428 51553
51358 51472 51450 51386 51358 51384 51369 51415 51409 51414 51415 51405 51397 51389 51287
51383 51346 51372 51349 51367 51442 51374 51404 51408 51398 51548 51415 51395 51402 51318
51364 51444 51465 51376 51347 51458 51469 51413 51401 51406 51405 51404 51406 51390 51319
51361 51433 51444 51386 51479 51353 51367 51419 51418 51402 51397 51409 51403 51406 51322
51384 51375 51371 51364 51363 51344 51391 51414 51415 51416 51409 51406 51401 51404 51320
51319 51445 51468 51334 51323 51328 51366 51410 51417 51402 51548 51404 51552 51391 51315
51355 51319 51371 51332 51443 51417 51322 51394 51409 51386 51398 51407 51397 51389 51321
51327 51344 51377 51361 51411 51440 51340 51413 51407 51276 51395 51411 51410 51390 51304
51406 51364 51358 51349 51479 51388 51365 51416 51396 51385 51413 51417 51396 51397 51315
51327 51346 51353 51378 51364 51375 51362 51420 51409 51387 51548 51418 51412 51393 51323
51355 51441 51445 51383 51360 51376 51341 51428 51413 51406 51400 51414 51403 51394 51322
51327 51463 51441 51369 51355 51377 51339 51413 51429 51397 51412 51410 51394 51391 51314
51356 51372 51347 51341 51409 51319 51367 51413 51422 51403 51401 51419 51398 51389 51289
51409 51439 51440 51379 51321 51357 51361 51416 51411 51407 51411 51407 51399 51391 51314
51473 51319 51446 51364 51360 51385 51343 51413 51411 51385 51402 51405 51397 51395 51287
51319 51444 51372 51382 51355 51385 51365 51411 51408 51400 51401 51406 51399 51391 51320
51326 51375 51372 51381 51412 51355 51365 51413 51414 51407 51415 51414 51397 51390 51318
51382 51440 51441 51385 51293 51349 51338 51416 51407 51408 51397 51399 51401 51397 51288

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 51304 bytes 100%
1,000 51286 bytes -18 bytes 100%
10,000 51282 bytes -4 bytes 100%
100,000 51279 bytes -3 bytes 2.61%
1,000,000 51276 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
51587 bytes +311 bytes (+0.61%) +251 bytes
51587 bytes +311 bytes (+0.61%) +251 bytes
51590 bytes +314 bytes (+0.61%) +254 bytes
51528 bytes +252 bytes (+0.49%) +192 bytes
51473 bytes +197 bytes (+0.38%) +137 bytes
51470 bytes +194 bytes (+0.38%) +134 bytes
51372 bytes +96 bytes (+0.19%) +36 bytes
51389 bytes +113 bytes (+0.22%) +53 bytes
51336 bytes +60 bytes (+0.12%)

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 40893 bytes -10383 bytes (-20.25%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 43506 bytes -7770 bytes (-15.15%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 44573 bytes -6703 bytes (-13.07%)
Brotli (Wikipedia) brotli brotli -q 11 46255 bytes -5021 bytes (-9.79%)
LZMA2 (Wikipedia) xz xz -9 47004 bytes -4272 bytes (-8.33%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 48963 bytes -2313 bytes (-4.51%)
ZSTD (Wikipedia) zstd zstd -19 49570 bytes -1706 bytes (-3.33%)

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