Choose a version:
32% The original file has 34669 bytes (33.9k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 11153 bytes (10.9k, 32%).

After GZIP compression these minified files vary in size:
Boot
  4255 bytes (4.2k)
CDN, direct link
gzip -6 (default)
  3820 bytes (3.7k)
local copy
gzip -9
  3816 bytes (3.7k)
local copy
cdnjs
  3815 bytes (3.7k)
CDN, direct link
cdnhttps
  3798 bytes (3.7k)
CDN, direct link
unpkg
  3792 bytes (3.7k)
CDN, direct link
libdeflate -12
  3716 bytes (3.6k)
local copy
7zip -mx=9 -tgzip
  3710 bytes (3.6k)
local copy
pigz -11 -n
  3709 bytes (3.6k)
local copy
kzip -s0 -rn -b1
  3708 bytes (3.6k)
local copy
Zopfli
  3707 bytes (3.6k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.2.min.js

You will automatically get the smallest BackboneJS 0.3.2 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 85 bytes by using my BackboneJS 0.3.2 Zopfli version instead of the best available CDN (2.29% smaller than unpkg, 3707 vs. 3792 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 --bsr2 --lazy --ohh

(found September 8, 2015)
Description Value Parameter
iterations 10000  --i10000
maximum blocks 8  --mb8
maximum length score 512  --mls512
block splitting recursion 2  --bsr2
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/0.3.2/backbone-min.js --location | md5sum
2b86430594cc9ce4439fd2e9fc8baa56  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.2.min.zopfli.js.gz | md5sum
2b86430594cc9ce4439fd2e9fc8baa56  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.3.2/backbone-min.js --location | sha1sum
768517dc26c24579b8b44ab6761bae9aa5b98b08  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.2.min.zopfli.js.gz | sha1sum
768517dc26c24579b8b44ab6761bae9aa5b98b08  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4255 bytes 2b86430594cc9ce4439fd2e9fc8baa56 (invalid)
cdnjs 3815 bytes 2b86430594cc9ce4439fd2e9fc8baa56 (invalid)
cdnhttps 3798 bytes 2b86430594cc9ce4439fd2e9fc8baa56 December 24, 2015 @ 07:32
unpkg 3792 bytes 2b86430594cc9ce4439fd2e9fc8baa56 July 11, 2016 @ 16:18

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
3707 bytes -1 byte zopfli --i10000 --mls512 --bsr2 --lazy --ohh September 8, 2015 @ 14:15
3708 bytes zopfli --i100 --mls2048 --bsr2 --lazy --ohh September 8, 2015 @ 11:32

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
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708
3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3707 3708 3708

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 3708 bytes 100%
1,000 3708 bytes 100%
10,000 3707 bytes -1 byte 100%
100,000 3707 bytes 0.29%
1,000,000 3707 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
3708 bytes +1 byte (+0.03%)
3708 bytes +1 byte (+0.03%)
3733 bytes +26 bytes (+0.70%) +25 bytes
3772 bytes +65 bytes (+1.75%) +64 bytes
3786 bytes +79 bytes (+2.13%) +78 bytes
3815 bytes +108 bytes (+2.91%) +107 bytes
3853 bytes +146 bytes (+3.94%) +145 bytes
3891 bytes +184 bytes (+4.96%) +183 bytes
3926 bytes +219 bytes (+5.91%) +218 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 3316 bytes -391 bytes (-10.55%)
Brotli (Wikipedia) brotli brotli -q 11 3345 bytes -362 bytes (-9.77%)
ZSTD (Wikipedia) zstd zstd -19 3732 bytes +25 bytes (+0.67%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 3767 bytes +60 bytes (+1.62%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 3779 bytes +72 bytes (+1.94%)
LZMA2 (Wikipedia) xz xz -9 3788 bytes +81 bytes (+2.19%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 4155 bytes +448 bytes (+12.09%)

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