Choose a version:
32% The original file has 47945 bytes (46.8k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 15552 bytes (15.2k, 32%).

After GZIP compression these minified files vary in size:
jsdelivr
  6673 bytes (6.5k)
CDN, direct link
Boot
  6153 bytes (6.0k)
CDN, direct link
Baidu
  5474 bytes (5.3k)
CDN, direct link
cdnjs
  5450 bytes (5.3k)
CDN, direct link
gzip -6 (default)
  5443 bytes (5.3k)
local copy
gzip -9
  5443 bytes (5.3k)
local copy
unpkg
  5432 bytes (5.3k)
CDN, direct link
cdnhttps
  5421 bytes (5.3k)
CDN, direct link
7zip -mx=9 -tgzip
  5305 bytes (5.2k)
local copy
libdeflate -12
  5303 bytes (5.2k)
local copy
kzip -s0 -rn -b0
  5295 bytes (5.2k)
local copy
pigz -11 -n
  5290 bytes (5.2k)
local copy
Zopfli
  5286 bytes (5.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-0.9.0.min.js

You will automatically get the smallest BackboneJS 0.9.0 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 135 bytes by using my BackboneJS 0.9.0 Zopfli version instead of the best available CDN (2.55% smaller than cdnhttps, 5286 vs. 5421 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 --i1000 --mb8 --mls4096 --bsr21 --lazy --ohh

(found September 23, 2015)
Description Value Parameter
iterations 1000  --i1000
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

Verify file integrity

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

MD5:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.9.0/backbone-min.js --location | md5sum
beeb0726f296ebf8435bdeff40151ec9  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.9.0.min.zopfli.js.gz | md5sum
beeb0726f296ebf8435bdeff40151ec9  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.9.0/backbone-min.js --location | sha1sum
aeb06cc84ad1c7c2fd54afd936376af3c9e4bcba  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.9.0.min.zopfli.js.gz | sha1sum
aeb06cc84ad1c7c2fd54afd936376af3c9e4bcba  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 6153 bytes beeb0726f296ebf8435bdeff40151ec9 (invalid)
cdnjs 5450 bytes beeb0726f296ebf8435bdeff40151ec9 (invalid)
unpkg 5432 bytes beeb0726f296ebf8435bdeff40151ec9 July 11, 2016 @ 16:18
cdnhttps 5421 bytes beeb0726f296ebf8435bdeff40151ec9 December 24, 2015 @ 07:32

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
jsdelivr 6673 bytes b4825a643cf8a5ebdf968ce26f7b5288 < // Backbone.js 0.9.0
> // Backbone.js 0.9.9
>
< (function(){var i=this,r=i.Backbone,s=Array.prototype.slic [...]
< d.next={});f.callback=b;f.context=c;d.tail=f.next={}}retur [...]
< a.push({next:c.next,tail:c.tail});for(e=s.call(arguments,1 [...]
< this._changed={};this._previousAttributes=f.clone(this.att [...]
< e;f.isObject(a)||a==null?(d=a,c=b):(d={},d[a]=b);c||(c={}) [...]
< f.has(b,e)!=f.has(n,e))this._changed[e]=a;if(!u)!c.silent& [...]
< save:function(a,b,c){var d;f.isObject(a)||a==null?(d=a,c=b [...]
[...]
(invalid)
Baidu 5474 bytes 2b3165119f34b5c1a1a583938ee2fbbd 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
5286 bytes -1 byte zopfli --i1000 --mls4096 --bsr21 --lazy --ohh September 23, 2015 @ 13:48
5287 bytes zopfli --i100 --mls2048 --bsr13 --lazy --ohh September 8, 2015 @ 11:33

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
5287 5287 5288 5287 5295 5295 5289 5289 5289 5295 5287 5290 5291 5292 5292
5294 5294 5294 5295 5287 5295 5295 5295 5295 5295 5287 5287 5292 5290 5290
5287 5287 5289 5288 5287 5287 5287 5289 5288 5287 5287 5287 5287 5287 5287
5289 5289 5287 5289 5288 5287 5295 5288 5288 5288 5287 5287 5287 5287 5287
5287 5287 5288 5287 5295 5295 5289 5289 5289 5295 5287 5287 5290 5289 5289
5295 5295 5288 5287 5287 5287 5287 5287 5287 5287 5287 5287 5287 5288 5288
5295 5295 5294 5287 5287 5287 5287 5290 5288 5287 5287 5287 5287 5287 5287
5287 5287 5287 5287 5287 5287 5287 5287 5287 5287 5287 5287 5287 5288 5288
5291 5291 5287 5287 5287 5287 5287 5287 5288 5287 5287 5290 5287 5289 5289
5287 5287 5287 5287 5288 5295 5287 5290 5289 5295 5287 5288 5288 5287 5287
5287 5287 5287 5287 5288 5287 5287 5287 5288 5287 5287 5288 5287 5287 5287
5295 5295 5287 5287 5287 5287 5295 5287 5288 5287 5295 5287 5288 5288 5288
5295 5295 5293 5288 5287 5295 5295 5295 5287 5287 5287 5287 5287 5288 5288
5287 5287 5288 5287 5287 5287 5287 5287 5288 5287 5287 5287 5287 5287 5287
5287 5287 5288 5287 5287 5287 5287 5287 5287 5287 5287 5287 5287 5288 5288
5295 5295 5292 5287 5287 5287 5287 5287 5288 5287 5287 5294 5287 5287 5287
5295 5295 5292 5294 5287 5287 5295 5288 5288 5295 5295 5287 5289 5287 5287
5295 5295 5287 5287 5288 5288 5287 5287 5291 5287 5287 5286 5287 5287 5287
5289 5289 5287 5287 5288 5287 5287 5287 5288 5287 5287 5287 5287 5287 5287
5291 5291 5287 5295 5288 5287 5287 5287 5288 5287 5287 5287 5287 5291 5291
5295 5295 5293 5295 5287 5287 5287 5287 5288 5288 5287 5287 5288 5288 5288
5287 5287 5287 5292 5287 5287 5287 5287 5288 5287 5287 5287 5288 5289 5289
5287 5287 5287 5287 5288 5287 5287 5287 5288 5287 5287 5287 5288 5288 5288

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 5287 bytes 100%
1,000 5286 bytes -1 byte 100%
10,000 5286 bytes 100%
100,000 5286 bytes 0.29%
1,000,000 5286 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
5295 bytes +9 bytes (+0.17%)
5295 bytes +9 bytes (+0.17%)
5326 bytes +40 bytes (+0.76%) +31 bytes
5352 bytes +66 bytes (+1.25%) +57 bytes
5368 bytes +82 bytes (+1.55%) +73 bytes
5412 bytes +126 bytes (+2.38%) +117 bytes
5451 bytes +165 bytes (+3.12%) +156 bytes
5481 bytes +195 bytes (+3.69%) +186 bytes
5516 bytes +230 bytes (+4.35%) +221 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 4688 bytes -598 bytes (-11.31%)
Brotli (Wikipedia) brotli brotli -q 11 4827 bytes -459 bytes (-8.68%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 5316 bytes +30 bytes (+0.57%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 5318 bytes +32 bytes (+0.61%)
ZSTD (Wikipedia) zstd zstd -19 5323 bytes +37 bytes (+0.70%)
LZMA2 (Wikipedia) xz xz -9 5384 bytes +98 bytes (+1.85%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 5528 bytes +242 bytes (+4.58%)

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