Choose a version:
32% The original file has 57071 bytes (55.7k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 18303 bytes (17.9k, 32%).

After GZIP compression these minified files vary in size:
Boot
  7255 bytes (7.1k)
CDN, direct link
Baidu
  6479 bytes (6.3k)
CDN, direct link
cdnjs
  6452 bytes (6.3k)
CDN, direct link
gzip -6 (default)
  6450 bytes (6.3k)
local copy
gzip -9
  6441 bytes (6.3k)
local copy
unpkg
  6434 bytes (6.3k)
CDN, direct link
cdnhttps
  6428 bytes (6.3k)
CDN, direct link
7zip -mx=9 -tgzip
  6261 bytes (6.1k)
local copy
pigz -11 -n
  6259 bytes (6.1k)
local copy
libdeflate -12
  6257 bytes (6.1k)
local copy
kzip -s0 -rn -b1
  6252 bytes (6.1k)
local copy
Zopfli
  6243 bytes (6.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-0.9.9.min.js

You will automatically get the smallest BackboneJS 0.9.9 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 185 bytes by using my BackboneJS 0.9.9 Zopfli version instead of the best available CDN (2.96% smaller than cdnhttps, 6243 vs. 6428 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 --bsr11 --lazy --ohh

(found November 27, 2015)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 1024  --mls1024
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

Verify file integrity

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

MD5:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.9.9/backbone-min.js --location | md5sum
a4f6f23f49cf77eaef2e00d7da09342c  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.9.9.min.zopfli.js.gz | md5sum
a4f6f23f49cf77eaef2e00d7da09342c  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.9.9/backbone-min.js --location | sha1sum
d52d756f20f3c2b3e8c424e973813d448b2fd903  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.9.9.min.zopfli.js.gz | sha1sum
d52d756f20f3c2b3e8c424e973813d448b2fd903  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 7255 bytes a4f6f23f49cf77eaef2e00d7da09342c (invalid)
cdnjs 6452 bytes a4f6f23f49cf77eaef2e00d7da09342c (invalid)
unpkg 6434 bytes a4f6f23f49cf77eaef2e00d7da09342c July 11, 2016 @ 16:18
cdnhttps 6428 bytes a4f6f23f49cf77eaef2e00d7da09342c December 24, 2015 @ 07:32

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 6479 bytes b4825a643cf8a5ebdf968ce26f7b5288 only whitespaces differ (invalid)

Note: only the MD5 hashes are shown to keep things simple.

Other Versions

Available BackboneJS versions at minime.stephan-brumme.com:

1.3.3, 1.3.2, 1.3.1, 1.3.0,
1.2.3, 1.2.2, 1.2.1, 1.2.0,
1.1.2, 1.1.1, 1.1.0,
1.0.0,
0.9.10, 0.9.9, 0.9.2, 0.9.1, 0.9.0,
0.3.3, 0.3.2, 0.3.1, 0.3.0,
0.2.0,
0.1.2, 0.1.1

The project site contains an overview how well these versions were compressed.
Other interesting projects are AngularJS, Bootstrap, D3, Dojo, Ember, jQuery, Knockout, lodash, React, Socket.IO, ThreeJS, UnderscoreJS and Vue.

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
6243 bytes -1 byte zopfli --i1000000 --mls1024 --bsr11 --lazy --ohh November 27, 2015 @ 15:03
6244 bytes -2 bytes zopfli --i10000 --mls1024 --bsr11 --lazy --ohh September 8, 2015 @ 13:19
6246 bytes -1 byte zopfli --i1000 --mls1024 --bsr4 --lazy --ohh September 8, 2015 @ 11:45
6247 bytes zopfli --i100 --mls1024 --bsr11 --lazy --ohh September 8, 2015 @ 11:31

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

Most recent activity on July 11, 2016 @ 16:18.

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
6247 6247 6247 6248 6252 6252 6252 6247 6248 6247 6248 6254 6249 6249 6248
6252 6255 6248 6246 6246 6247 6246 6247 6246 6244 6249 6255 6249 6247 6247
6252 6254 6253 6252 6247 6246 6247 6252 6250 6250 6255 6248 6247 6248 6248
6247 6248 6247 6246 6246 6247 6247 6248 6247 6244 6255 6249 6247 6247 6247
6247 6247 6247 6248 6247 6247 6246 6247 6247 6246 6248 6248 6247 6248 6249
6252 6247 6253 6252 6252 6252 6252 6247 6247 6255 6255 6249 6249 6248 6249
6247 6248 6247 6246 6247 6247 6246 6252 6247 6244 6246 6248 6248 6247 6249
6246 6248 6248 6247 6247 6247 6246 6247 6248 6243 6255 6249 6247 6248 6248
6246 6248 6247 6246 6246 6246 6246 6247 6247 6246 6255 6249 6247 6249 6249
6247 6248 6247 6246 6246 6247 6246 6247 6247 6246 6255 6249 6246 6246 6246
6248 6248 6248 6249 6246 6248 6247 6247 6247 6247 6249 6249 6247 6247 6247
6252 6247 6246 6246 6246 6248 6246 6247 6246 6244 6255 6249 6247 6247 6247
6246 6247 6247 6246 6246 6247 6246 6247 6248 6244 6249 6248 6246 6247 6247
6247 6248 6247 6248 6246 6248 6247 6248 6248 6247 6255 6248 6250 6247 6247
6252 6248 6247 6246 6247 6247 6246 6252 6249 6246 6247 6247 6248 6248 6247
6246 6247 6246 6248 6247 6247 6246 6248 6249 6244 6255 6249 6247 6247 6247
6248 6246 6248 6248 6246 6247 6246 6247 6249 6246 6246 6249 6248 6248 6247
6248 6248 6248 6249 6246 6247 6247 6248 6248 6250 6255 6248 6247 6248 6248
6247 6248 6248 6247 6247 6247 6247 6248 6247 6244 6246 6248 6247 6248 6248
6247 6247 6247 6249 6246 6247 6247 6247 6247 6244 6255 6249 6249 6248 6248
6248 6248 6248 6249 6246 6247 6246 6247 6247 6246 6255 6249 6247 6249 6249
6246 6247 6246 6246 6246 6247 6247 6247 6247 6245 6247 6248 6248 6247 6247
6246 6248 6247 6248 6246 6248 6246 6247 6249 6246 6246 6249 6249 6249 6249

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 6247 bytes 100%
1,000 6246 bytes -1 byte 100%
10,000 6244 bytes -2 bytes 100%
100,000 6244 bytes 2.61%
1,000,000 6243 bytes -1 byte 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
6252 bytes +9 bytes (+0.14%)
6252 bytes +9 bytes (+0.14%)
6269 bytes +26 bytes (+0.42%) +17 bytes
6282 bytes +39 bytes (+0.62%) +30 bytes
6311 bytes +68 bytes (+1.09%) +59 bytes
6338 bytes +95 bytes (+1.52%) +86 bytes
6376 bytes +133 bytes (+2.13%) +124 bytes
6412 bytes +169 bytes (+2.71%) +160 bytes
6442 bytes +199 bytes (+3.19%) +190 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
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 5461 bytes -782 bytes (-12.53%)
Brotli (Wikipedia) brotli brotli -q 11 5727 bytes -516 bytes (-8.27%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 5944 bytes -299 bytes (-4.79%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 6150 bytes -93 bytes (-1.49%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 6221 bytes -22 bytes (-0.35%)
ZSTD (Wikipedia) zstd zstd -19 6278 bytes +35 bytes (+0.56%)
LZMA2 (Wikipedia) xz xz -9 6284 bytes +41 bytes (+0.66%)

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