Choose a version:
33% The original file has 59498 bytes (58.1k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 19457 bytes (19.0k, 33%).

After GZIP compression these minified files vary in size:
Boot
  7480 bytes (7.3k)
CDN, direct link
unpkg
  7349 bytes (7.2k)
CDN, direct link
Baidu
  6462 bytes (6.3k)
CDN, direct link
cdnjs
  6459 bytes (6.3k)
CDN, direct link
gzip -6 (default)
  6455 bytes (6.3k)
local copy
gzip -9
  6446 bytes (6.3k)
local copy
Sina
  6433 bytes (6.3k)
CDN, direct link
cdnhttps
  6433 bytes (6.3k)
CDN, direct link
Yandex
  6425 bytes (6.3k)
CDN, direct link
jsdelivr
  6425 bytes (6.3k)
CDN, direct link
7zip -mx=9 -tgzip
  6261 bytes (6.1k)
local copy
libdeflate -12
  6261 bytes (6.1k)
local copy
pigz -11 -n
  6257 bytes (6.1k)
local copy
kzip -s0 -rn -b0
  6255 bytes (6.1k)
local copy
Zopfli
  6248 bytes (6.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-1.0.0.min.js

You will automatically get the smallest BackboneJS 1.0.0 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 177 bytes by using my BackboneJS 1.0.0 Zopfli version instead of the best available CDN (2.83% smaller than jsdelivr, 6248 vs. 6425 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 --i10000 --mb8 --mls16384 --bsr21 --lazy --ohh

(found November 18, 2015)
Description Value Parameter
iterations 10000  --i10000
maximum blocks 8  --mb8
maximum length score 16384  --mls16384
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

Verify file integrity

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

MD5:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/1.0.0/backbone-min.js --location | md5sum
9cfbc78dc7eb8ac72cc3af1bec8ce7ee  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.0.0.min.zopfli.js.gz | md5sum
9cfbc78dc7eb8ac72cc3af1bec8ce7ee  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/1.0.0/backbone-min.js --location | sha1sum
89218fd4c321457a82aac6e4d3b5a50088745155  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.0.0.min.zopfli.js.gz | sha1sum
89218fd4c321457a82aac6e4d3b5a50088745155  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 7480 bytes 9cfbc78dc7eb8ac72cc3af1bec8ce7ee (invalid)
cdnjs 6459 bytes 9cfbc78dc7eb8ac72cc3af1bec8ce7ee (invalid)
Sina 6433 bytes 9cfbc78dc7eb8ac72cc3af1bec8ce7ee (invalid)
cdnhttps 6433 bytes 9cfbc78dc7eb8ac72cc3af1bec8ce7ee December 24, 2015 @ 07:32
Yandex 6425 bytes 9cfbc78dc7eb8ac72cc3af1bec8ce7ee (invalid)
jsdelivr 6425 bytes 9cfbc78dc7eb8ac72cc3af1bec8ce7ee (invalid)

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
unpkg 7349 bytes f18da2d38e372f6a594537c9ef7fb347 < (function(){var t=this;var e=t.Backbone;var i=[];var r=i.p [...]
> (function(){var root=this;var previousBackbone=root.Backbo [...]
July 11, 2016 @ 16:18
Baidu 6462 bytes 52a3911cc70c2b120b670eb73d0f7a5f 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
6248 bytes -1 byte zopfli --i10000 --mls16384 --bsr21 --lazy --ohh November 18, 2015 @ 02:53
6249 bytes -2 bytes zopfli --i1000 --mls8192 --bsr9 --lazy --ohh September 8, 2015 @ 14:59
6251 bytes -1 byte zopfli --i1000 --mls1024 --bsr10 --lazy --ohh September 8, 2015 @ 14:58
6252 bytes zopfli --i100 --mls1024 --bsr6 --lazy --ohh September 8, 2015 @ 14:57

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 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
6254 6254 6253 6253 6253 6253 6255 6254 6251 6255 6253 6253 6253 6253 6253
6253 6253 6249 6253 6253 6251 6259 6259 6251 6252 6254 6254 6249 6249 6249
6253 6252 6251 6252 6255 6251 6253 6253 6252 6251 6253 6251 6250 6252 6253
6253 6253 6253 6250 6251 6251 6255 6253 6252 6251 6253 6250 6249 6249 6249
6254 6252 6255 6253 6255 6254 6251 6254 6252 6252 6254 6250 6249 6249 6249
6253 6253 6253 6250 6251 6251 6251 6253 6252 6253 6253 6253 6249 6249 6249
6253 6252 6253 6254 6255 6253 6253 6252 6250 6251 6254 6255 6249 6249 6249
6253 6253 6250 6250 6252 6253 6253 6253 6251 6253 6253 6250 6249 6249 6250
6253 6253 6253 6255 6255 6251 6255 6254 6257 6254 6253 6250 6249 6251 6250
6251 6251 6253 6255 6252 6252 6255 6253 6253 6252 6253 6250 6250 6250 6250
6253 6252 6251 6250 6255 6252 6251 6253 6252 6251 6254 6250 6249 6250 6250
6253 6253 6255 6253 6254 6253 6251 6254 6252 6251 6253 6254 6249 6249 6253
6254 6251 6255 6251 6255 6252 6251 6253 6252 6252 6253 6254 6250 6249 6249
6253 6253 6253 6251 6250 6254 6250 6253 6252 6251 6254 6250 6249 6249 6249
6253 6253 6254 6255 6255 6251 6251 6253 6257 6255 6253 6250 6249 6250 6251
6253 6253 6252 6250 6253 6251 6251 6254 6252 6249 6254 6250 6249 6250 6250
6253 6253 6255 6250 6255 6251 6251 6254 6251 6253 6253 6251 6251 6251 6250
6253 6254 6254 6255 6250 6250 6251 6251 6252 6251 6254 6250 6249 6248 6250
6253 6254 6255 6250 6254 6252 6252 6253 6252 6256 6254 6250 6249 6249 6249
6253 6253 6250 6255 6254 6252 6252 6253 6252 6256 6253 6250 6250 6249 6249
6253 6252 6250 6250 6255 6252 6255 6253 6252 6251 6253 6254 6249 6249 6251
6253 6253 6253 6251 6254 6253 6252 6254 6253 6254 6253 6249 6249 6249 6250
6253 6254 6250 6250 6252 6253 6251 6253 6252 6253 6254 6253 6250 6249 6250

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 6251 bytes 100%
1,000 6249 bytes -2 bytes 100%
10,000 6248 bytes -1 byte 100%
100,000 6248 bytes 0.29%
1,000,000 6248 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
6255 bytes +7 bytes (+0.11%)
6255 bytes +7 bytes (+0.11%)
6273 bytes +25 bytes (+0.40%) +18 bytes
6304 bytes +56 bytes (+0.90%) +49 bytes
6339 bytes +91 bytes (+1.46%) +84 bytes
6358 bytes +110 bytes (+1.76%) +103 bytes
6380 bytes +132 bytes (+2.11%) +125 bytes
6416 bytes +168 bytes (+2.69%) +161 bytes
6447 bytes +199 bytes (+3.19%) +192 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 5450 bytes -798 bytes (-12.77%)
Brotli (Wikipedia) brotli brotli -q 11 5793 bytes -455 bytes (-7.28%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 5881 bytes -367 bytes (-5.87%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 6191 bytes -57 bytes (-0.91%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 6217 bytes -31 bytes (-0.50%)
ZSTD (Wikipedia) zstd zstd -19 6253 bytes +5 bytes (+0.08%)
LZMA2 (Wikipedia) xz xz -9 6284 bytes +36 bytes (+0.58%)

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