Choose a version:
33% The original file has 61015 bytes (59.6k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 20004 bytes (19.5k, 33%).

After GZIP compression these minified files vary in size:
Boot
  7701 bytes (7.5k)
CDN, direct link
Baidu
  6701 bytes (6.5k)
CDN, direct link
cdnjs
  6696 bytes (6.5k)
CDN, direct link
gzip -6 (default)
  6679 bytes (6.5k)
local copy
gzip -9
  6674 bytes (6.5k)
local copy
unpkg
  6669 bytes (6.5k)
CDN, direct link
cdnhttps
  6659 bytes (6.5k)
CDN, direct link
Yandex
  6652 bytes (6.5k)
CDN, direct link
7zip -mx=9 -tgzip
  6502 bytes (6.3k)
local copy
libdeflate -12
  6493 bytes (6.3k)
local copy
pigz -11 -n
  6490 bytes (6.3k)
local copy
kzip -s0 -rn -b1
  6487 bytes (6.3k)
local copy
Zopfli
  6483 bytes (6.3k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-1.1.1.min.js

You will automatically get the smallest BackboneJS 1.1.1 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 169 bytes by using my BackboneJS 1.1.1 Zopfli version instead of the best available CDN (2.61% smaller than Yandex, 6483 vs. 6652 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 --mls4096 --bsr9 --lazy --ohh

(found November 18, 2015)
Description Value Parameter
iterations 100000  --i100000
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/1.1.1/backbone-min.js --location | md5sum
54dea01fc5bfa946537fbad8c98b7505  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.1.1.min.zopfli.js.gz | md5sum
54dea01fc5bfa946537fbad8c98b7505  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/1.1.1/backbone-min.js --location | sha1sum
b7a1bd4fb9a9a7d8ec3b352d91104795c3924bdc  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-1.1.1.min.zopfli.js.gz | sha1sum
b7a1bd4fb9a9a7d8ec3b352d91104795c3924bdc  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
unpkg 6669 bytes 54dea01fc5bfa946537fbad8c98b7505 July 11, 2016 @ 16:18

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Boot 7701 bytes deb2fd0f79695f722f766c387751e286 only whitespaces differ (invalid)
Baidu 6701 bytes 7bf5eefcb7f5b17a50a3b5be6b7e85c4 only whitespaces differ (invalid)
cdnjs 6696 bytes deb2fd0f79695f722f766c387751e286 only whitespaces differ (invalid)
cdnhttps 6659 bytes deb2fd0f79695f722f766c387751e286 only whitespaces differ December 24, 2015 @ 07:32
Yandex 6652 bytes deb2fd0f79695f722f766c387751e286 only whitespaces differ (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
6483 bytes -1 byte zopfli --i100000 --mls4096 --bsr9 --lazy --ohh November 18, 2015 @ 04:58
6484 bytes -2 bytes zopfli --i1000 --mls4096 --bsr11 --lazy --ohh September 8, 2015 @ 11:42
6486 bytes -1 byte zopfli --i1000 --mls512 --bsr4 --lazy --ohh September 8, 2015 @ 11:42
6487 bytes zopfli --i100 --mls4096 --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 or 100,000.
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
6489 6489 6489 6489 6489 6489 6489 6489 6489 6486 6490 6490 6488 6488 6488
6488 6491 6489 6490 6491 6489 6489 6487 6486 6486 6487 6485 6485 6484 6486
6489 6489 6487 6489 6489 6490 6489 6489 6488 6489 6488 6485 6486 6485 6485
6489 6487 6489 6489 6489 6489 6489 6487 6487 6486 6488 6485 6486 6483 6485
6489 6489 6490 6489 6489 6489 6489 6488 6487 6488 6489 6483 6486 6487 6483
6489 6491 6489 6489 6489 6489 6489 6487 6485 6487 6489 6483 6485 6485 6485
6489 6488 6487 6488 6489 6490 6489 6487 6487 6489 6488 6485 6486 6485 6485
6489 6488 6488 6489 6490 6489 6489 6487 6485 6486 6489 6483 6486 6489 6483
6489 6488 6487 6486 6489 6489 6489 6489 6489 6488 6488 6489 6486 6486 6486
6489 6488 6489 6489 6487 6489 6485 6489 6485 6486 6489 6483 6486 6485 6486
6489 6488 6489 6489 6489 6488 6490 6489 6486 6486 6488 6484 6485 6485 6485
6488 6489 6490 6489 6490 6488 6490 6487 6487 6490 6485 6490 6486 6486 6483
6489 6489 6490 6489 6489 6490 6489 6487 6486 6486 6485 6489 6486 6483 6486
6488 6488 6488 6489 6490 6490 6488 6489 6487 6485 6488 6484 6486 6485 6485
6489 6488 6487 6489 6490 6490 6488 6489 6487 6489 6488 6489 6483 6488 6486
6488 6488 6489 6489 6486 6488 6489 6489 6485 6484 6489 6483 6485 6485 6485
6489 6488 6488 6489 6489 6488 6483 6489 6485 6484 6488 6484 6485 6487 6486
6489 6489 6487 6489 6490 6490 6488 6489 6487 6489 6489 6485 6491 6483 6486
6490 6489 6489 6487 6489 6489 6485 6487 6487 6486 6488 6485 6486 6487 6486
6489 6488 6487 6486 6489 6489 6489 6489 6487 6489 6489 6483 6486 6487 6486
6489 6487 6487 6487 6489 6488 6489 6489 6487 6486 6488 6483 6486 6487 6486
6489 6490 6488 6485 6489 6490 6485 6487 6487 6486 6488 6489 6485 6485 6486
6488 6487 6489 6489 6490 6488 6489 6488 6485 6489 6488 6483 6485 6487 6486

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 6487 bytes 100%
1,000 6484 bytes -3 bytes 100%
10,000 6484 bytes 100%
100,000 6483 bytes -1 byte 6.38%
1,000,000
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
6487 bytes +4 bytes (+0.06%)
6487 bytes +4 bytes (+0.06%)
6513 bytes +30 bytes (+0.46%) +26 bytes
6546 bytes +63 bytes (+0.97%) +59 bytes
6578 bytes +95 bytes (+1.47%) +91 bytes
6611 bytes +128 bytes (+1.97%) +124 bytes
6629 bytes +146 bytes (+2.25%) +142 bytes
6653 bytes +170 bytes (+2.62%) +166 bytes
6686 bytes +203 bytes (+3.13%) +199 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 5679 bytes -804 bytes (-12.40%)
Brotli (Wikipedia) brotli brotli -q 11 6016 bytes -467 bytes (-7.20%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 6087 bytes -396 bytes (-6.11%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 6431 bytes -52 bytes (-0.80%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 6445 bytes -38 bytes (-0.59%)
ZSTD (Wikipedia) zstd zstd -19 6491 bytes +8 bytes (+0.12%)
LZMA2 (Wikipedia) xz xz -9 6532 bytes +49 bytes (+0.76%)

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