Choose a version:
47% The original file has 298068 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 139289 bytes (136.0k, 47%).

After GZIP compression these minified files vary in size:
Boot
  54426 bytes (53.2k)
CDN, direct link
Baidu
  47483 bytes (46.4k)
CDN, direct link
cdnjs
  47472 bytes (46.4k)
CDN, direct link
gzip -6 (default)
  47146 bytes (46.0k)
local copy
cdnhttps
  47117 bytes (46.0k)
CDN, direct link
unpkg
  47064 bytes (46.0k)
CDN, direct link
gzip -9
  46976 bytes (45.9k)
local copy
7zip -mx=9 -tgzip
  45470 bytes (44.4k)
local copy
libdeflate -12
  45425 bytes (44.4k)
local copy
kzip -s0 -rn -b7
  45354 bytes (44.3k)
local copy
pigz -11 -n
  45268 bytes (44.2k)
local copy
Zopfli
  45168 bytes (44.1k)
local copy
Zopfli (defluff)
  45167 bytes (44.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-3.1.8.min.js

You will automatically get the smallest D3 3.1.8 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 1896 bytes by using my D3 3.1.8 Zopfli version instead of the best available CDN (4.20% smaller than unpkg, 45168 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 --bsr11 --lazy --ohh

(found December 21, 2015)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 4096  --mls4096
block splitting recursion 11  --bsr11
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 (45167 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/v3.1.8/d3.min.js --location | md5sum
9019eee58664b2df71441b64d570e475  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.8.min.zopfli.js.gz | md5sum
9019eee58664b2df71441b64d570e475  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.1.8/d3.min.js --location | sha1sum
5af0f277a462397e06d463cad53996a583e6d6c5  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.1.8.min.zopfli.js.gz | sha1sum
5af0f277a462397e06d463cad53996a583e6d6c5  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 54426 bytes 9019eee58664b2df71441b64d570e475 (invalid)
cdnjs 47472 bytes 9019eee58664b2df71441b64d570e475 (invalid)
cdnhttps 47117 bytes 9019eee58664b2df71441b64d570e475 December 24, 2015 @ 07:33
unpkg 47064 bytes 9019eee58664b2df71441b64d570e475 July 11, 2016 @ 16:32

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 47483 bytes 2577355fdc0f6cd5c4ef16abe5bf81f9 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:

4.11.0, 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
45168 bytes -6 bytes zopfli --i100000 --mls4096 --bsr11 --lazy --ohh December 21, 2015 @ 13:40
45174 bytes -1 byte zopfli --i10000 --mls4096 --bsr11 --lazy --ohh November 23, 2015 @ 17:33
45175 bytes -5 bytes zopfli --i10000 --mls128 --bsr14 --lazy --ohh November 23, 2015 @ 17:28
45180 bytes -8 bytes zopfli --i1000 --mls128 --bsr14 --lazy --ohh September 20, 2015 @ 09:24
45188 bytes zopfli --i100 --mls4096 --bsr11 --lazy --ohh September 18, 2015 @ 21:03

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 @ 09:11.

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
45352 45352 45351 45351 45350 45366 45318 45372 45348 45350 45344 45368 45376 45367 45346
45273 45277 45260 45277 45267 45232 45256 45360 45200 45189 45201 45198 45363 45376 45325
45234 45352 45262 45211 45269 45187 45186 45198 45220 45216 45179 45297 45376 45376 45363
45352 45358 45273 45257 45260 45205 45235 45329 45230 45229 45216 45357 45375 45374 45367
45234 45232 45235 45280 45232 45213 45213 45240 45207 45242 45253 45352 45377 45372 45377
45252 45256 45232 45244 45244 45240 45204 45329 45202 45201 45194 45354 45370 45371 45371
45360 45215 45347 45254 45224 45187 45221 45213 45332 45353 45256 45356 45377 45376 45377
45241 45263 45252 45246 45246 45219 45231 45227 45197 45204 45205 45168 45377 45376 45377
45245 45231 45255 45248 45261 45213 45232 45227 45196 45222 45259 45351 45382 45371 45378
45227 45353 45228 45263 45240 45358 45240 45220 45196 45192 45244 45193 45378 45348 45377
45206 45258 45258 45264 45246 45364 45171 45234 45190 45216 45193 45352 45354 45376 45355
45235 45220 45268 45252 45201 45240 45247 45305 45196 45201 45324 45370 45360 45374 45367
45357 45250 45220 45254 45231 45235 45219 45318 45315 45326 45178 45365 45366 45370 45377
45219 45224 45249 45283 45251 45348 45253 45354 45372 45202 45198 45213 45376 45374 45377
45229 45346 45354 45248 45256 45223 45218 45225 45372 45209 45240 45362 45376 45377 45212
45248 45343 45243 45272 45300 45347 45240 45231 45371 45199 45247 45355 45383 45377 45381
45241 45239 45228 45348 45207 45219 45244 45326 45199 45234 45267 45315 45359 45371 45377
45211 45273 45248 45256 45257 45219 45233 45208 45327 45201 45199 45189 45376 45371 45378
45204 45253 45342 45260 45243 45221 45273 45303 45329 45192 45239 45353 45365 45375 45376
45346 45338 45341 45243 45238 45214 45245 45219 45365 45220 45204 45355 45377 45374 45377
45195 45335 45272 45245 45198 45204 45281 45218 45198 45204 45254 45355 45378 45344 45377
45339 45228 45215 45258 45196 45214 45257 45214 45369 45190 45227 45354 45383 45375 45377
45328 45230 45255 45251 45256 45201 45247 45295 45188 45270 45241 45354 45377 45376 45375

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 45188 bytes 100%
1,000 45180 bytes -8 bytes 100%
10,000 45174 bytes -6 bytes 100%
100,000 45168 bytes -6 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
45394 bytes +226 bytes (+0.50%) +40 bytes
45396 bytes +228 bytes (+0.50%) +42 bytes
45387 bytes +219 bytes (+0.48%) +33 bytes
45395 bytes +227 bytes (+0.50%) +41 bytes
45425 bytes +257 bytes (+0.57%) +71 bytes
45432 bytes +264 bytes (+0.58%) +78 bytes
45404 bytes +236 bytes (+0.52%) +50 bytes
45354 bytes +186 bytes (+0.41%)
45361 bytes +193 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 36294 bytes -8874 bytes (-19.65%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 38347 bytes -6821 bytes (-15.10%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 38826 bytes -6342 bytes (-14.04%)
Brotli (Wikipedia) brotli brotli -q 11 40847 bytes -4321 bytes (-9.57%)
LZMA2 (Wikipedia) xz xz -9 41608 bytes -3560 bytes (-7.88%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 43381 bytes -1787 bytes (-3.96%)
ZSTD (Wikipedia) zstd zstd -19 43557 bytes -1611 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