Choose a version:
32% The original file has 72236 bytes (70.5k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 23355 bytes (22.8k, 32%).

After GZIP compression these minified files vary in size:
Boot
  8830 bytes (8.6k)
CDN, direct link
cdnjs
  7603 bytes (7.4k)
CDN, direct link
gzip -6 (default)
  7582 bytes (7.4k)
local copy
gzip -9
  7576 bytes (7.4k)
local copy
cdnhttps
  7563 bytes (7.4k)
CDN, direct link
unpkg
  7563 bytes (7.4k)
CDN, direct link
jsdelivr
  7559 bytes (7.4k)
CDN, direct link
pigz -11 -n
  7343 bytes (7.2k)
local copy
libdeflate -12
  7341 bytes (7.2k)
local copy
7zip -mx=9 -tgzip
  7339 bytes (7.2k)
local copy
Zopfli
  7335 bytes (7.2k)
local copy
kzip -s0 -rn -b1
  7334 bytes (7.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-1.3.3.min.js

You will automatically get the smallest BackboneJS 1.3.3 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 224 bytes by using my BackboneJS 1.3.3 Zopfli version instead of the best available CDN (3.05% smaller than jsdelivr, 7335 vs. 7559 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 --i100000 --mb8 --mls32768 --bsr22 --lazy --ohh

(found March 29, 2016)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 32768  --mls32768
block splitting recursion 22  --bsr22
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/1.3.3/backbone-min.js --location | md5sum
1f542a03bb9e6203b95cc9d0c39e0af7  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.3.3.min.zopfli.js.gz | md5sum
1f542a03bb9e6203b95cc9d0c39e0af7  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/1.3.3/backbone-min.js --location | sha1sum
cedae44e9eb034dd29fd414e89f2a123773d10f4  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.3.3.min.zopfli.js.gz | sha1sum
cedae44e9eb034dd29fd414e89f2a123773d10f4  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 8830 bytes 1f542a03bb9e6203b95cc9d0c39e0af7 May 3, 2016 @ 10:57
cdnjs 7603 bytes 1f542a03bb9e6203b95cc9d0c39e0af7 April 5, 2016 @ 20:16
cdnhttps 7563 bytes 1f542a03bb9e6203b95cc9d0c39e0af7 November 22, 2016 @ 16:29
unpkg 7563 bytes 1f542a03bb9e6203b95cc9d0c39e0af7 July 11, 2016 @ 16:17
jsdelivr 7559 bytes 1f542a03bb9e6203b95cc9d0c39e0af7 April 5, 2016 @ 22:38

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 and UnderscoreJS.

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
7335 bytes -1 byte zopfli --i100000 --mls32768 --bsr22 --lazy --ohh March 29, 2016 @ 12:17
7336 bytes -1 byte zopfli --i10000 --mls32768 --bsr22 --lazy --ohh March 29, 2016 @ 12:09
7337 bytes zopfli --i100 --mls16384 --bsr13 --lazy --ohh March 29, 2016 @ 12:04

If there are multiple parameter sets yielding the same compressed size, only the first one found is shown.

Most recent activity on November 22, 2016 @ 16:29.

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
7339 7338 7337 7338 7338 7338 7338 7338 7339 7339 7339 7339 7337 7337 7337
7339 7344 7340 7339 7339 7339 7339 7345 7340 7338 7338 7339 7338 7341 7341
7338 7338 7338 7341 7342 7339 7339 7342 7339 7338 7337 7337 7339 7342 7342
7339 7336 7339 7339 7339 7339 7339 7339 7340 7338 7339 7337 7344 7339 7339
7340 7338 7339 7338 7338 7338 7339 7343 7338 7338 7337 7337 7344 7337 7337
7338 7336 7338 7339 7339 7339 7339 7339 7338 7338 7337 7339 7344 7339 7342
7338 7339 7340 7342 7339 7339 7339 7343 7338 7338 7337 7337 7343 7337 7335
7339 7340 7340 7339 7338 7339 7339 7338 7339 7338 7337 7337 7339 7338 7338
7338 7337 7339 7338 7340 7339 7342 7342 7338 7338 7337 7337 7337 7335 7340
7338 7337 7339 7338 7339 7339 7339 7342 7337 7338 7339 7337 7339 7335 7338
7338 7337 7339 7339 7339 7339 7339 7342 7338 7339 7335 7337 7338 7340 7339
7336 7337 7339 7338 7340 7339 7338 7343 7339 7337 7339 7335 7337 7339 7340
7338 7337 7338 7338 7341 7339 7339 7343 7339 7338 7338 7335 7337 7339 7335
7336 7338 7339 7339 7339 7339 7342 7342 7337 7338 7337 7337 7344 7342 7339
7338 7338 7338 7338 7340 7339 7339 7343 7338 7338 7337 7337 7337 7338 7339
7338 7337 7338 7339 7340 7339 7339 7342 7338 7338 7337 7337 7338 7339 7339
7338 7337 7339 7338 7340 7339 7342 7342 7339 7338 7337 7337 7339 7342 7342
7338 7336 7340 7340 7340 7339 7337 7338 7337 7338 7337 7337 7337 7340 7338
7338 7337 7340 7340 7340 7339 7339 7342 7338 7338 7337 7338 7343 7337 7335
7338 7337 7339 7338 7342 7339 7339 7345 7338 7338 7337 7337 7338 7337 7337
7338 7337 7340 7340 7340 7339 7342 7342 7337 7338 7337 7337 7337 7335 7339
7337 7337 7342 7339 7342 7338 7342 7342 7339 7338 7339 7337 7342 7339 7340
7338 7337 7338 7338 7340 7338 7339 7343 7337 7338 7338 7337 7338 7337 7337

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 7337 bytes 100%
1,000 7336 bytes -1 byte 100%
10,000 7336 bytes 100%
100,000 7335 bytes -1 byte 4.06%
1,000,000 7335 bytes 2.61%
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
7334 bytes -1 byte (-0.01%)
7334 bytes -1 byte (-0.01%)
7356 bytes +21 bytes (+0.29%) +22 bytes
7384 bytes +49 bytes (+0.67%) +50 bytes
7414 bytes +79 bytes (+1.08%) +80 bytes
7428 bytes +93 bytes (+1.27%) +94 bytes
7471 bytes +136 bytes (+1.85%) +137 bytes
7503 bytes +168 bytes (+2.29%) +169 bytes
7529 bytes +194 bytes (+2.64%) +195 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 6371 bytes -964 bytes (-13.14%)
Brotli (Wikipedia) brotli brotli -q 11 6863 bytes -472 bytes (-6.43%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 6901 bytes -434 bytes (-5.92%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 7000 bytes -335 bytes (-4.57%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 7231 bytes -104 bytes (-1.42%)
ZSTD (Wikipedia) zstd zstd -19 7325 bytes -10 bytes (-0.14%)
LZMA2 (Wikipedia) xz xz -9 7352 bytes +17 bytes (+0.23%)

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