Choose a version:
32% The original file has 24751 bytes (24.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 7814 bytes (7.6k, 32%).

After GZIP compression these minified files vary in size:
Boot
  2942 bytes (2.9k)
CDN, direct link
gzip -6 (default)
  2655 bytes (2.6k)
local copy
gzip -9
  2655 bytes (2.6k)
local copy
cdnjs
  2644 bytes (2.6k)
CDN, direct link
cdnhttps
  2633 bytes (2.6k)
CDN, direct link
unpkg
  2633 bytes (2.6k)
CDN, direct link
libdeflate -12
  2578 bytes (2.5k)
local copy
7zip -mx=9 -tgzip
  2577 bytes (2.5k)
local copy
kzip -s0 -rn -b1
  2575 bytes (2.5k)
local copy
pigz -11 -n
  2574 bytes (2.5k)
local copy
Zopfli
  2573 bytes (2.5k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-0.2.0.min.js

You will automatically get the smallest BackboneJS 0.2.0 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 60 bytes by using my BackboneJS 0.2.0 Zopfli version instead of the best available CDN (2.33% smaller than unpkg, 2573 vs. 2633 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 --mls512 --bsr6 --lazy --ohh

(found September 8, 2015)
Description Value Parameter
iterations 1000  --i1000
maximum blocks 8  --mb8
maximum length score 512  --mls512
block splitting recursion 6  --bsr6
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/0.2.0/backbone-min.js --location | md5sum
2b9be58c38587f242d383879488e668d  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.2.0.min.zopfli.js.gz | md5sum
2b9be58c38587f242d383879488e668d  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.2.0/backbone-min.js --location | sha1sum
6cb272172c500d67267bc339c60c06e79a83662a  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.2.0.min.zopfli.js.gz | sha1sum
6cb272172c500d67267bc339c60c06e79a83662a  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 2942 bytes 2b9be58c38587f242d383879488e668d (invalid)
cdnjs 2644 bytes 2b9be58c38587f242d383879488e668d (invalid)
cdnhttps 2633 bytes 2b9be58c38587f242d383879488e668d December 24, 2015 @ 07:32
unpkg 2633 bytes 2b9be58c38587f242d383879488e668d 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
2573 bytes -1 byte zopfli --i1000 --mls512 --bsr6 --lazy --ohh September 8, 2015 @ 11:51
2574 bytes zopfli --i100 --mls512 --bsr9 --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
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573
2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573 2573

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 2574 bytes 100%
1,000 2573 bytes -1 byte 100%
10,000 2573 bytes 100%
100,000 2573 bytes 0.29%
1,000,000 2573 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
2575 bytes +2 bytes (+0.08%)
2575 bytes +2 bytes (+0.08%)
2610 bytes +37 bytes (+1.44%) +35 bytes
2638 bytes +65 bytes (+2.53%) +63 bytes
2678 bytes +105 bytes (+4.08%) +103 bytes
2716 bytes +143 bytes (+5.56%) +141 bytes
2752 bytes +179 bytes (+6.96%) +177 bytes
2776 bytes +203 bytes (+7.89%) +201 bytes
2807 bytes +234 bytes (+9.09%) +232 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 2317 bytes -256 bytes (-9.95%)
Brotli (Wikipedia) brotli brotli -q 11 2329 bytes -244 bytes (-9.48%)
ZSTD (Wikipedia) zstd zstd -19 2603 bytes +30 bytes (+1.17%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 2639 bytes +66 bytes (+2.57%)
LZMA2 (Wikipedia) xz xz -9 2680 bytes +107 bytes (+4.16%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 2940 bytes +367 bytes (+14.26%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 3219 bytes +646 bytes (+25.11%)

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