Choose a version:
45% The original file has 326272 bytes (318.6k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 146525 bytes (143.1k, 45%).

After GZIP compression these minified files vary in size:
Boot
  58633 bytes (57.3k)
CDN
Baidu
  51688 bytes (50.5k)
CDN
cdnjs
  51676 bytes (50.5k)
CDN
unpkg
  51380 bytes (50.2k)
CDN
gzip -6 (default)
  51295 bytes (50.1k)
local copy
cdnhttps
  51283 bytes (50.1k)
CDN
gzip -9
  51137 bytes (49.9k)
local copy
libdeflate -12
  49492 bytes (48.3k)
local copy
7zip -mx=9 -tgzip
  49400 bytes (48.2k)
local copy
kzip -s0 -rn -b8
  49174 bytes (48.0k)
local copy
pigz -11 -n
  49171 bytes (48.0k)
local copy
Zopfli
  49097 bytes (47.9k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/d3/d3-3.4.8.min.js

You will automatically get the smallest D3 3.4.8 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 2186 bytes by using my D3 3.4.8 Zopfli version instead of the best available CDN (4.45% smaller than cdnhttps, 49097 vs. 51283 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 --mls1024 --bsr16 --lazy --ohh

(found December 22, 2015)
Description Value Parameter
iterations 100000  --i100000
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

Verify file integrity

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

MD5:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.4.8/d3.min.js --location | md5sum
8e2ed78d07426a8ba81629f3dbd3069b  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.4.8.min.zopfli.js.gz | md5sum
8e2ed78d07426a8ba81629f3dbd3069b  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/mbostock/d3/v3.4.8/d3.min.js --location | sha1sum
24e9cffeb10576736b39ef2a71b5c5c5d3242173  -
curl --silent --compressed http://minime.stephan-brumme.com/files/d3/d3-3.4.8.min.zopfli.js.gz | sha1sum
24e9cffeb10576736b39ef2a71b5c5c5d3242173  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 58633 bytes 8e2ed78d07426a8ba81629f3dbd3069b (invalid)
cdnjs 51676 bytes 8e2ed78d07426a8ba81629f3dbd3069b (invalid)
unpkg 51380 bytes 8e2ed78d07426a8ba81629f3dbd3069b July 11, 2016 @ 16:31
cdnhttps 51283 bytes 8e2ed78d07426a8ba81629f3dbd3069b December 24, 2015 @ 07:33

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 51688 bytes 17c1f6b50029040462b6c1fea815b7b7 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:

5.1.0, 5.0.1, 5.0.0,
4.13.0, 4.12.2, 4.12.1, 4.12.0, 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
49097 bytes -6 bytes zopfli --i100000 --mls1024 --bsr16 --lazy --ohh December 22, 2015 @ 14:30
49103 bytes -8 bytes zopfli --i10000 --mls1024 --bsr16 --lazy --ohh October 13, 2015 @ 19:37
49111 bytes -1 byte zopfli --i1000 --mls1024 --bsr16 --lazy --ohh September 19, 2015 @ 08:31
49112 bytes -6 bytes zopfli --i1000 --mls512 --bsr4 --lazy --ohh September 19, 2015 @ 08:17
49118 bytes -9 bytes zopfli --i1000 --mls256 --bsr6 --lazy --ohh September 19, 2015 @ 08:13
49127 bytes -4 bytes zopfli --i1000 --mls16 --bsr14 --lazy --ohh September 19, 2015 @ 08:01
49131 bytes zopfli --i100 --mls1024 --bsr16 --lazy --ohh September 18, 2015 @ 19:44

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

Most recent activity on February 23, 2017 @ 23:40.

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
49248 49251 49249 49251 49251 49260 49260 49262 49257 49267 49266 49343 49361 49227 49360
49140 49123 49124 49159 49149 49175 49138 49131 49107 49214 49198 49248 49357 49221 49358
49159 49233 49157 49155 49155 49125 49124 49114 49145 49158 49196 49360 49357 49364 49359
49114 49169 49158 49153 49150 49136 49126 49213 49133 49210 49201 49227 49357 49222 49221
49174 49219 49206 49151 49192 49181 49133 49134 49137 49107 49225 49220 49357 49206 49243
49168 49185 49282 49169 49161 49144 49122 49213 49217 49117 49199 49213 49357 49201 49205
49171 49202 49150 49170 49160 49130 49123 49125 49134 49117 49198 49220 49358 49210 49200
49165 49192 49218 49151 49164 49130 49131 49127 49108 49118 49204 49216 49357 49205 49204
49165 49205 49260 49156 49157 49175 49131 49125 49132 49120 49195 49216 49357 49204 49202
49171 49209 49150 49173 49149 49145 49122 49127 49133 49124 49200 49202 49356 49221 49203
49113 49125 49157 49121 49173 49142 49130 49132 49134 49123 49198 49213 49357 49211 49204
49171 49127 49159 49130 49162 49129 49123 49132 49138 49131 49203 49215 49357 49199 49200
49157 49183 49151 49152 49159 49143 49123 49136 49134 49097 49200 49220 49356 49202 49206
49173 49184 49149 49168 49161 49188 49124 49132 49131 49120 49198 49210 49357 49201 49211
49171 49176 49157 49169 49165 49180 49128 49139 49134 49213 49198 49212 49357 49203 49204
49109 49201 49159 49176 49155 49128 49125 49131 49134 49216 49196 49219 49356 49202 49211
49161 49184 49145 49159 49139 49172 49127 49127 49134 49123 49195 49208 49357 49211 49236
49166 49203 49150 49151 49156 49145 49127 49128 49141 49120 49203 49213 49357 49202 49207
49166 49180 49156 49129 49175 49187 49127 49139 49136 49215 49201 49220 49358 49209 49206
49252 49200 49157 49173 49178 49173 49128 49130 49133 49120 49198 49213 49356 49200 49220
49174 49155 49153 49170 49174 49186 49129 49133 49133 49118 49207 49225 49356 49203 49203
49174 49198 49167 49127 49122 49111 49131 49208 49137 49121 49199 49212 49357 49201 49201
49170 49204 49169 49171 49160 49135 49127 49126 49136 49199 49203 49212 49358 49202 49202

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 49131 bytes 100%
1,000 49111 bytes -20 bytes 100%
10,000 49103 bytes -8 bytes 100%
100,000 49097 bytes -6 bytes 0.87%
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
49383 bytes +286 bytes (+0.58%) +209 bytes
49386 bytes +289 bytes (+0.59%) +212 bytes
49400 bytes +303 bytes (+0.62%) +226 bytes
49420 bytes +323 bytes (+0.66%) +246 bytes
49351 bytes +254 bytes (+0.52%) +177 bytes
49349 bytes +252 bytes (+0.51%) +175 bytes
49314 bytes +217 bytes (+0.44%) +140 bytes
49216 bytes +119 bytes (+0.24%) +42 bytes
49174 bytes +77 bytes (+0.16%)

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 39136 bytes -9961 bytes (-20.29%)
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 41567 bytes -7530 bytes (-15.34%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 42454 bytes -6643 bytes (-13.53%)
Brotli (Wikipedia) brotli brotli -q 11 44351 bytes -4746 bytes (-9.67%)
LZMA2 (Wikipedia) xz xz -9 45072 bytes -4025 bytes (-8.20%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 46802 bytes -2295 bytes (-4.67%)
ZSTD (Wikipedia) zstd zstd -19 47465 bytes -1632 bytes (-3.32%)

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 2018.
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