Choose a version:
33% The original file has 21678 bytes (21.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 7203 bytes (7.0k, 33%).

After GZIP compression these minified files vary in size:
Boot
  2748 bytes (2.7k)
CDN, direct link
gzip -6 (default)
  2509 bytes (2.5k)
local copy
gzip -9
  2506 bytes (2.4k)
local copy
cdnjs
  2481 bytes (2.4k)
CDN, direct link
cdnhttps
  2466 bytes (2.4k)
CDN, direct link
unpkg
  2466 bytes (2.4k)
CDN, direct link
libdeflate -12
  2437 bytes (2.4k)
local copy
pigz -11 -n
  2436 bytes (2.4k)
local copy
kzip -s0 -rn -b1
  2434 bytes (2.4k)
local copy
Zopfli
  2434 bytes (2.4k)
local copy
7zip -mx=9 -tgzip
  2431 bytes (2.4k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-0.1.1.min.js

You will automatically get the smallest BackboneJS 0.1.1 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 32 bytes by using my BackboneJS 0.1.1 Zopfli version instead of the best available CDN (1.31% smaller than unpkg, 2434 vs. 2466 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 --mls512 --bsr4 --lazy --ohh

(found September 8, 2015)
Description Value Parameter
iterations 10000  --i10000
maximum blocks 8  --mb8
maximum length score 512  --mls512
block splitting recursion 4  --bsr4
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/0.1.1/backbone-min.js --location | md5sum
5f029a7bdb17421211bc938438939270  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.1.1.min.zopfli.js.gz | md5sum
5f029a7bdb17421211bc938438939270  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.1.1/backbone-min.js --location | sha1sum
c4c5c50b38ee3acde3dc75a789e557eba91874ae  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.1.1.min.zopfli.js.gz | sha1sum
c4c5c50b38ee3acde3dc75a789e557eba91874ae  -

CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Boot 2748 bytes 65fa0f0689f823821d73d3cd841524af < f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
< b);return a},get:function(a){return a&&this._byId[a.id!=nu [...]
< f.Model))a=e.map(a,function(d){return new c.model(d)});thi [...]
< _reset:function(){this.length=0;this.models=[];this._byId= [...]
< delete this._byCid[a.cid];delete a.collection;this.models. [...]
< "any","include","invoke","max","min","sortBy","sortedIndex [...]
< function(a){return h(a,this.el)},k=/^(\w+)\s*(.*)$/;e.exte [...]
< e.extend({},this.options,a);if(a.model)this.model=a.model; [...]
< success:c,error:d})}})();
> f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
[...]
(invalid)
cdnjs 2481 bytes 65fa0f0689f823821d73d3cd841524af < f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
< b);return a},get:function(a){return a&&this._byId[a.id!=nu [...]
< f.Model))a=e.map(a,function(d){return new c.model(d)});thi [...]
< _reset:function(){this.length=0;this.models=[];this._byId= [...]
< delete this._byCid[a.cid];delete a.collection;this.models. [...]
< "any","include","invoke","max","min","sortBy","sortedIndex [...]
< function(a){return h(a,this.el)},k=/^(\w+)\s*(.*)$/;e.exte [...]
< e.extend({},this.options,a);if(a.model)this.model=a.model; [...]
< success:c,error:d})}})();
> f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
[...]
(invalid)
cdnhttps 2466 bytes 65fa0f0689f823821d73d3cd841524af < f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
< b);return a},get:function(a){return a&&this._byId[a.id!=nu [...]
< f.Model))a=e.map(a,function(d){return new c.model(d)});thi [...]
< _reset:function(){this.length=0;this.models=[];this._byId= [...]
< delete this._byCid[a.cid];delete a.collection;this.models. [...]
< "any","include","invoke","max","min","sortBy","sortedIndex [...]
< function(a){return h(a,this.el)},k=/^(\w+)\s*(.*)$/;e.exte [...]
< e.extend({},this.options,a);if(a.model)this.model=a.model; [...]
< success:c,error:d})}})();
> f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
[...]
December 24, 2015 @ 07:32
unpkg 2466 bytes 65fa0f0689f823821d73d3cd841524af < f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
< b);return a},get:function(a){return a&&this._byId[a.id!=nu [...]
< f.Model))a=e.map(a,function(d){return new c.model(d)});thi [...]
< _reset:function(){this.length=0;this.models=[];this._byId= [...]
< delete this._byCid[a.cid];delete a.collection;this.models. [...]
< "any","include","invoke","max","min","sortBy","sortedIndex [...]
< function(a){return h(a,this.el)},k=/^(\w+)\s*(.*)$/;e.exte [...]
< e.extend({},this.options,a);if(a.model)this.model=a.model; [...]
< success:c,error:d})}})();
> f.Collection=function(a,b){b||(b={});if(b.comparator){this [...]
[...]
July 11, 2016 @ 16:19

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
2434 bytes -1 byte zopfli --i10000 --mls512 --bsr4 --lazy --ohh September 8, 2015 @ 14:39
2435 bytes -1 byte zopfli --i1000 --mls512 --bsr14 --lazy --ohh September 8, 2015 @ 11:52
2436 bytes zopfli --i100 --mls512 --bsr12 --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 @ 16:19.

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
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2434 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2434 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2434 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2434 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2435 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434
2434 2434 2434 2434 2434 2435 2434 2434 2434 2435 2434 2434 2434 2434 2434

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 2436 bytes 100%
1,000 2435 bytes -1 byte 100%
10,000 2434 bytes -1 byte 100%
100,000 2434 bytes 4.93%
1,000,000 2434 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
2434 bytes – (0.00%)
2434 bytes – (0.00%)
2466 bytes +32 bytes (+1.31%) +32 bytes
2501 bytes +67 bytes (+2.75%) +67 bytes
2535 bytes +101 bytes (+4.15%) +101 bytes
2554 bytes +120 bytes (+4.93%) +120 bytes
2594 bytes +160 bytes (+6.57%) +160 bytes
2630 bytes +196 bytes (+8.05%) +196 bytes
2665 bytes +231 bytes (+9.49%) +231 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 2191 bytes -243 bytes (-9.98%)
Brotli (Wikipedia) brotli brotli -q 11 2217 bytes -217 bytes (-8.92%)
ZSTD (Wikipedia) zstd zstd -19 2468 bytes +34 bytes (+1.40%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 2485 bytes +51 bytes (+2.10%)
LZMA2 (Wikipedia) xz xz -9 2556 bytes +122 bytes (+5.01%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 2669 bytes +235 bytes (+9.65%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 3094 bytes +660 bytes (+27.12%)

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