Choose a version:
32% The original file has 35706 bytes (34.9k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 11550 bytes (11.3k, 32%).

After GZIP compression these minified files vary in size:
Boot
  4424 bytes (4.3k)
CDN, direct link
Baidu
  3975 bytes (3.9k)
CDN, direct link
cdnjs
  3958 bytes (3.9k)
CDN, direct link
gzip -6 (default)
  3954 bytes (3.9k)
local copy
gzip -9
  3952 bytes (3.9k)
local copy
cdnhttps
  3932 bytes (3.8k)
CDN, direct link
unpkg
  3931 bytes (3.8k)
CDN, direct link
libdeflate -12
  3848 bytes (3.8k)
local copy
7zip -mx=9 -tgzip
  3843 bytes (3.8k)
local copy
pigz -11 -n
  3843 bytes (3.8k)
local copy
kzip -s0 -rn -b0
  3842 bytes (3.8k)
local copy
Zopfli
  3839 bytes (3.7k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.3.min.js

You will automatically get the smallest BackboneJS 0.3.3 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 92 bytes by using my BackboneJS 0.3.3 Zopfli version instead of the best available CDN (2.40% smaller than unpkg, 3839 vs. 3931 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 --mls2048 --bsr2 --lazy --ohh

(found September 8, 2015)
Description Value Parameter
iterations 1000  --i1000
maximum blocks 8  --mb8
maximum length score 2048  --mls2048
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/0.3.3/backbone-min.js --location | md5sum
5c8053a6fab598f46af8d7e59bfc0ce1  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.3.min.zopfli.js.gz | md5sum
5c8053a6fab598f46af8d7e59bfc0ce1  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/0.3.3/backbone-min.js --location | sha1sum
f29dc890697e78d412a5e06da3623c76cbd80b07  -
curl --silent --compressed http://minime.stephan-brumme.com/files/backbonejs/backbone-0.3.3.min.zopfli.js.gz | sha1sum
f29dc890697e78d412a5e06da3623c76cbd80b07  -

These CDNs send you the original file:
CDN Size (compressed) MD5 (uncompressed) Timestamp
Boot 4424 bytes 5c8053a6fab598f46af8d7e59bfc0ce1 (invalid)
cdnjs 3958 bytes 5c8053a6fab598f46af8d7e59bfc0ce1 (invalid)
cdnhttps 3932 bytes 5c8053a6fab598f46af8d7e59bfc0ce1 December 24, 2015 @ 07:32
unpkg 3931 bytes 5c8053a6fab598f46af8d7e59bfc0ce1 July 11, 2016 @ 16:18

And some CDNs send you a different file:
CDN Size (compressed) MD5 (uncompressed) Comment / Diff Timestamp
Baidu 3975 bytes 5d7dc1cbe7f0b177cf66187937001fb9 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
3839 bytes -1 byte zopfli --i1000 --mls2048 --bsr2 --lazy --ohh September 8, 2015 @ 11:49
3840 bytes -2 bytes zopfli --i1000 --mls512 --bsr9 --lazy --ohh September 8, 2015 @ 11:49
3842 bytes zopfli --i100 --mls512 --bsr14 --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
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3846 3846
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3846 3846
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3846 3846
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840
3840 3840 3840 3840 3840 3840 3840 3840 3840 3840 3839 3840 3840 3840 3840

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 3842 bytes 100%
1,000 3839 bytes -3 bytes 100%
10,000 3839 bytes 100%
100,000 3839 bytes 0.29%
1,000,000 3839 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
3842 bytes +3 bytes (+0.08%)
3842 bytes +3 bytes (+0.08%)
3868 bytes +29 bytes (+0.76%) +26 bytes
3907 bytes +68 bytes (+1.77%) +65 bytes
3922 bytes +83 bytes (+2.16%) +80 bytes
3952 bytes +113 bytes (+2.94%) +110 bytes
3991 bytes +152 bytes (+3.96%) +149 bytes
4023 bytes +184 bytes (+4.79%) +181 bytes
4064 bytes +225 bytes (+5.86%) +222 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 3440 bytes -399 bytes (-10.39%)
Brotli (Wikipedia) brotli brotli -q 11 3453 bytes -386 bytes (-10.05%)
ZSTD (Wikipedia) zstd zstd -19 3863 bytes +24 bytes (+0.63%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 3879 bytes +40 bytes (+1.04%)
LZMA2 (Wikipedia) xz xz -9 3916 bytes +77 bytes (+2.01%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 3926 bytes +87 bytes (+2.27%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 4275 bytes +436 bytes (+11.36%)

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