Choose a version:
47% The original file has 298055 bytes (291.1k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 139279 bytes (136.0k, 47%).

After GZIP compression these minified files vary in size:
Boot
  54420 bytes (53.1k)
CDN, direct link
Baidu
  47481 bytes (46.4k)
CDN, direct link
cdnjs
  47470 bytes (46.4k)
CDN, direct link
gzip -6 (default)
  47142 bytes (46.0k)
local copy
cdnhttps
  47115 bytes (46.0k)
CDN, direct link
unpkg
  47064 bytes (46.0k)
CDN, direct link
gzip -9
  46973 bytes (45.9k)
local copy
7zip -mx=9 -tgzip
  45466 bytes (44.4k)
local copy
libdeflate -12
  45422 bytes (44.4k)
local copy
kzip -s0 -rn -b7
  45349 bytes (44.3k)
local copy
pigz -11 -n
  45275 bytes (44.2k)
local copy
Zopfli
  45160 bytes (44.1k)
local copy
Zopfli (defluff)
  45158 bytes (44.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-3.1.9.min.js

You will automatically get the smallest D3 3.1.9 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 1904 bytes by using my D3 3.1.9 Zopfli version instead of the best available CDN (4.22% smaller than unpkg, 45160 vs. 47064 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 --mls4096 --bsr21 --lazy --ohh

(found December 21, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 4096  --mls4096
block splitting recursion 21  --bsr21
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 (45158 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/v3.1.9/d3.min.js --location | md5sum
f71db8685e4d9f9d54d4a4d1dba2f12e  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.9.min.zopfli.js.gz | md5sum
f71db8685e4d9f9d54d4a4d1dba2f12e  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.1.9/d3.min.js --location | sha1sum
f77854aa8fe2049c8f0c23a63629bdfc884e093e  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.9.min.zopfli.js.gz | sha1sum
f77854aa8fe2049c8f0c23a63629bdfc884e093e  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 54420 bytes f71db8685e4d9f9d54d4a4d1dba2f12e (invalid)
cdnjs 47470 bytes f71db8685e4d9f9d54d4a4d1dba2f12e (invalid)
cdnhttps 47115 bytes f71db8685e4d9f9d54d4a4d1dba2f12e December 24, 2015 @ 07:33
unpkg 47064 bytes f71db8685e4d9f9d54d4a4d1dba2f12e July 11, 2016 @ 16:32

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 47481 bytes db32214162e235817e2af2642a3da2bd 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:

4.10.0,
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
45160 bytes -4 bytes zopfli --i100000 --mls4096 --bsr21 --lazy --ohh December 21, 2015 @ 14:03
45164 bytes -6 bytes zopfli --i10000 --mls4096 --bsr21 --lazy --ohh September 23, 2015 @ 17:38
45170 bytes -3 bytes zopfli --i1000 --mls4096 --bsr21 --lazy --ohh September 23, 2015 @ 16:40
45173 bytes -3 bytes zopfli --i1000 --mls2048 --bsr12 --lazy --ohh September 20, 2015 @ 09:06
45176 bytes -8 bytes zopfli --i1000 --mls128 --bsr14 --lazy --ohh September 20, 2015 @ 08:39
45184 bytes zopfli --i100 --mls4096 --bsr11 --lazy --ohh September 18, 2015 @ 20:56

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 @ 08:40.

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
45354 45348 45349 45348 45347 45362 45315 45368 45344 45345 45340 45363 45371 45363 45343
45270 45273 45257 45274 45262 45227 45272 45356 45197 45190 45252 45193 45356 45373 45322
45275 45240 45259 45243 45266 45221 45185 45202 45222 45216 45176 45292 45372 45372 45359
45211 45357 45274 45249 45258 45189 45230 45320 45226 45210 45213 45350 45372 45370 45363
45226 45229 45230 45276 45231 45196 45213 45217 45203 45236 45208 45352 45374 45368 45374
45226 45249 45229 45242 45242 45245 45191 45324 45195 45196 45191 45353 45370 45365 45367
45356 45215 45344 45251 45220 45184 45217 45235 45346 45306 45253 45303 45374 45372 45374
45336 45259 45249 45248 45251 45248 45228 45284 45192 45227 45202 45169 45374 45373 45371
45204 45227 45261 45250 45257 45210 45219 45249 45197 45217 45170 45352 45378 45365 45374
45205 45245 45255 45255 45231 45356 45218 45250 45187 45189 45267 45192 45374 45343 45373
45220 45256 45230 45246 45243 45232 45172 45218 45186 45213 45194 45353 45350 45373 45351
45235 45248 45265 45249 45196 45227 45246 45237 45191 45194 45313 45302 45373 45371 45363
45257 45211 45222 45257 45228 45229 45228 45315 45309 45325 45176 45358 45372 45366 45375
45210 45224 45249 45286 45247 45210 45234 45350 45367 45202 45196 45346 45371 45362 45374
45334 45224 45263 45246 45255 45220 45229 45248 45366 45194 45283 45358 45373 45374 45212
45253 45222 45254 45270 45293 45343 45215 45227 45367 45194 45242 45349 45367 45364 45374
45237 45352 45227 45247 45206 45223 45229 45324 45188 45218 45246 45319 45366 45366 45374
45241 45273 45249 45238 45256 45221 45217 45203 45325 45199 45196 45160 45360 45366 45374
45214 45253 45211 45261 45195 45216 45269 45216 45324 45186 45231 45350 45362 45373 45373
45341 45336 45337 45251 45256 45227 45265 45221 45263 45213 45237 45187 45374 45370 45372
45169 45332 45269 45252 45193 45178 45216 45228 45187 45198 45214 45299 45375 45340 45374
45215 45347 45212 45216 45196 45213 45254 45213 45366 45189 45226 45350 45363 45373 45373
45233 45300 45249 45247 45253 45197 45244 45291 45185 45250 45211 45171 45374 45364 45376

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 45177 bytes 100%
1,000 45170 bytes -7 bytes 100%
10,000 45164 bytes -6 bytes 100%
100,000 45160 bytes -4 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
45386 bytes +226 bytes (+0.50%) +37 bytes
45393 bytes +233 bytes (+0.52%) +44 bytes
45387 bytes +227 bytes (+0.50%) +38 bytes
45390 bytes +230 bytes (+0.51%) +41 bytes
45422 bytes +262 bytes (+0.58%) +73 bytes
45426 bytes +266 bytes (+0.59%) +77 bytes
45405 bytes +245 bytes (+0.54%) +56 bytes
45349 bytes +189 bytes (+0.42%)
45356 bytes +196 bytes (+0.43%) +7 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 36291 bytes -8869 bytes (-19.64%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 38353 bytes -6807 bytes (-15.07%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 38825 bytes -6335 bytes (-14.03%)
Brotli (Wikipedia) brotli brotli -q 11 40857 bytes -4303 bytes (-9.53%)
LZMA2 (Wikipedia) xz xz -9 41592 bytes -3568 bytes (-7.90%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 43389 bytes -1771 bytes (-3.92%)
ZSTD (Wikipedia) zstd zstd -19 43550 bytes -1610 bytes (-3.57%)

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