Choose a version:
32% The original file has 71365 bytes (69.7k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 23062 bytes (22.5k, 32%).

After GZIP compression these minified files vary in size:
Boot
  8712 bytes (8.5k)
CDN, direct link
cdnjs
  7521 bytes (7.3k)
CDN, direct link
gzip -6 (default)
  7496 bytes (7.3k)
local copy
gzip -9
  7488 bytes (7.3k)
local copy
unpkg
  7485 bytes (7.3k)
CDN, direct link
cdnhttps
  7474 bytes (7.3k)
CDN, direct link
jsdelivr
  7470 bytes (7.3k)
CDN, direct link
libdeflate -12
  7287 bytes (7.1k)
local copy
pigz -11 -n
  7261 bytes (7.1k)
local copy
7zip -mx=9 -tgzip
  7257 bytes (7.1k)
local copy
Zopfli
  7252 bytes (7.1k)
local copy
kzip -s0 -rn -b0
  7251 bytes (7.1k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-1.2.2.min.js

You will automatically get the smallest BackboneJS 1.2.2 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 218 bytes by using my BackboneJS 1.2.2 Zopfli version instead of the best available CDN (3.01% smaller than jsdelivr, 7252 vs. 7470 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 --mls4096 --bsr9 --lazy --ohh

(found November 27, 2015)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 4096  --mls4096
block splitting recursion 9  --bsr9
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/1.2.2/backbone-min.js --location | md5sum
f633f1a2a8ebc39a3ffffbf9e6418bcb  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.2.2.min.zopfli.js.gz | md5sum
f633f1a2a8ebc39a3ffffbf9e6418bcb  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/1.2.2/backbone-min.js --location | sha1sum
1c3a7a8b88d907e6c291e861f084d3efd39b583d  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.2.2.min.zopfli.js.gz | sha1sum
1c3a7a8b88d907e6c291e861f084d3efd39b583d  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 8712 bytes f633f1a2a8ebc39a3ffffbf9e6418bcb (invalid)
cdnjs 7521 bytes f633f1a2a8ebc39a3ffffbf9e6418bcb (invalid)
unpkg 7485 bytes f633f1a2a8ebc39a3ffffbf9e6418bcb July 11, 2016 @ 16:18
cdnhttps 7474 bytes f633f1a2a8ebc39a3ffffbf9e6418bcb December 24, 2015 @ 07:32
jsdelivr 7470 bytes f633f1a2a8ebc39a3ffffbf9e6418bcb (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
7252 bytes -1 byte zopfli --i1000000 --mls4096 --bsr9 --lazy --ohh November 27, 2015 @ 16:50
7253 bytes -1 byte zopfli --i10000 --mls4096 --bsr9 --lazy --ohh September 8, 2015 @ 12:07
7254 bytes -1 byte zopfli --i1000 --mls1024 --bsr6 --lazy --ohh September 8, 2015 @ 11:38
7255 bytes zopfli --i100 --mls1024 --bsr11 --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, 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
7254 7254 7255 7254 7254 7255 7254 7254 7262 7254 7253 7254 7256 7255 7255
7254 7255 7258 7260 7261 7256 7259 7259 7259 7254 7254 7255 7256 7255 7255
7256 7255 7254 7255 7255 7254 7258 7259 7254 7254 7254 7254 7255 7254 7255
7253 7256 7254 7255 7259 7254 7254 7258 7254 7256 7256 7254 7257 7254 7255
7254 7255 7254 7254 7254 7254 7254 7253 7259 7256 7256 7254 7255 7255 7255
7254 7255 7255 7255 7254 7257 7260 7255 7254 7258 7254 7252 7255 7255 7255
7254 7256 7255 7255 7259 7254 7254 7259 7253 7256 7254 7254 7254 7257 7257
7254 7255 7254 7254 7254 7254 7258 7254 7258 7254 7256 7254 7256 7257 7255
7253 7256 7254 7255 7255 7255 7254 7254 7254 7256 7255 7254 7255 7257 7256
7254 7255 7258 7255 7261 7254 7254 7254 7254 7254 7253 7253 7254 7253 7255
7254 7254 7255 7254 7255 7259 7264 7253 7254 7256 7254 7253 7255 7254 7255
7254 7255 7254 7255 7261 7256 7258 7258 7254 7256 7256 7255 7257 7254 7254
7254 7256 7255 7254 7255 7254 7264 7254 7255 7256 7253 7253 7256 7255 7255
7254 7256 7255 7255 7255 7257 7258 7253 7263 7255 7256 7254 7254 7255 7255
7255 7254 7267 7255 7255 7257 7258 7254 7255 7256 7255 7254 7254 7254 7254
7254 7255 7254 7255 7255 7256 7256 7254 7255 7253 7253 7254 7257 7257 7254
7254 7255 7254 7255 7255 7256 7258 7254 7255 7254 7256 7255 7257 7254 7254
7254 7255 7254 7255 7255 7255 7258 7254 7255 7256 7254 7254 7254 7254 7253
7254 7255 7254 7255 7255 7254 7258 7260 7255 7254 7254 7254 7255 7254 7255
7255 7255 7254 7255 7255 7255 7259 7254 7254 7255 7253 7254 7257 7257 7255
7254 7255 7254 7255 7255 7254 7254 7259 7255 7256 7254 7254 7256 7254 7255
7254 7255 7254 7254 7255 7256 7256 7254 7254 7256 7254 7254 7257 7254 7254
7254 7256 7254 7255 7255 7254 7255 7258 7255 7256 7255 7254 7254 7255 7255

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 7254 bytes 100%
1,000 7254 bytes 100%
10,000 7253 bytes -1 byte 100%
100,000 7253 bytes 20.29%
1,000,000 7252 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
7251 bytes -1 byte (-0.01%)
7251 bytes -1 byte (-0.01%)
7274 bytes +22 bytes (+0.30%) +23 bytes
7303 bytes +51 bytes (+0.70%) +52 bytes
7332 bytes +80 bytes (+1.10%) +81 bytes
7348 bytes +96 bytes (+1.32%) +97 bytes
7389 bytes +137 bytes (+1.89%) +138 bytes
7419 bytes +167 bytes (+2.30%) +168 bytes
7449 bytes +197 bytes (+2.72%) +198 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 6289 bytes -963 bytes (-13.28%)
Brotli (Wikipedia) brotli brotli -q 11 6786 bytes -466 bytes (-6.43%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 6794 bytes -458 bytes (-6.32%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 6929 bytes -323 bytes (-4.45%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 7149 bytes -103 bytes (-1.42%)
ZSTD (Wikipedia) zstd zstd -19 7239 bytes -13 bytes (-0.18%)
LZMA2 (Wikipedia) xz xz -9 7264 bytes +12 bytes (+0.17%)

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