Choose a version:
32% The original file has 33589 bytes (32.8k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 10907 bytes (10.7k, 32%).

After GZIP compression these minified files vary in size:
Boot
  4193 bytes (4.1k)
CDN, direct link
cdnjs
  3746 bytes (3.7k)
CDN, direct link
gzip -6 (default)
  3745 bytes (3.7k)
local copy
gzip -9
  3744 bytes (3.7k)
local copy
unpkg
  3724 bytes (3.6k)
CDN, direct link
cdnhttps
  3723 bytes (3.6k)
CDN, direct link
libdeflate -12
  3649 bytes (3.6k)
local copy
7zip -mx=9 -tgzip
  3643 bytes (3.6k)
local copy
kzip -s0 -rn -b1
  3641 bytes (3.6k)
local copy
pigz -11 -n
  3641 bytes (3.6k)
local copy
Zopfli
  3639 bytes (3.6k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.0.min.js

You will automatically get the smallest BackboneJS 0.3.0 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 84 bytes by using my BackboneJS 0.3.0 Zopfli version instead of the best available CDN (2.31% smaller than cdnhttps, 3639 vs. 3723 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 --mls512 --bsr8 --lazy --ohh

(found November 27, 2015)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 512  --mls512
block splitting recursion 8  --bsr8
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/0.3.0/backbone-min.js --location | md5sum
5d10787d656341eef98bd0eb99a33f73  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.0.min.zopfli.js.gz | md5sum
5d10787d656341eef98bd0eb99a33f73  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.3.0/backbone-min.js --location | sha1sum
c1d4b6a42a7e8946494c095fe253adf8e8161e65  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.0.min.zopfli.js.gz | sha1sum
c1d4b6a42a7e8946494c095fe253adf8e8161e65  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4193 bytes 5d10787d656341eef98bd0eb99a33f73 (invalid)
cdnjs 3746 bytes 5d10787d656341eef98bd0eb99a33f73 (invalid)
unpkg 3724 bytes 5d10787d656341eef98bd0eb99a33f73 July 11, 2016 @ 16:18
cdnhttps 3723 bytes 5d10787d656341eef98bd0eb99a33f73 December 24, 2015 @ 07:32

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
3639 bytes -1 byte zopfli --i1000000 --mls512 --bsr8 --lazy --ohh November 27, 2015 @ 13:46
3640 bytes zopfli --i100 --mls512 --bsr8 --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 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
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3639 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640
3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640 3640

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 3640 bytes 100%
1,000 3640 bytes 100%
10,000 3640 bytes 100%
100,000 3640 bytes 0.29%
1,000,000 3639 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
3641 bytes +2 bytes (+0.05%)
3641 bytes +2 bytes (+0.05%)
3668 bytes +29 bytes (+0.80%) +27 bytes
3707 bytes +68 bytes (+1.87%) +66 bytes
3720 bytes +81 bytes (+2.23%) +79 bytes
3760 bytes +121 bytes (+3.33%) +119 bytes
3800 bytes +161 bytes (+4.42%) +159 bytes
3832 bytes +193 bytes (+5.30%) +191 bytes
3862 bytes +223 bytes (+6.13%) +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 3265 bytes -374 bytes (-10.28%)
Brotli (Wikipedia) brotli brotli -q 11 3290 bytes -349 bytes (-9.59%)
ZSTD (Wikipedia) zstd zstd -19 3658 bytes +19 bytes (+0.52%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 3680 bytes +41 bytes (+1.13%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 3712 bytes +73 bytes (+2.01%)
LZMA2 (Wikipedia) xz xz -9 3720 bytes +81 bytes (+2.23%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 4105 bytes +466 bytes (+12.81%)

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