Choose a version:
32% The original file has 77794 bytes (76.0k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 25006 bytes (24.4k, 32%).

After GZIP compression these minified files vary in size:
unpkg
  9537 bytes (9.3k)
CDN
Boot
  8038 bytes (7.8k)
CDN
cdnjs
  8038 bytes (7.8k)
CDN
gzip -6 (default)
  8018 bytes (7.8k)
local copy
gzip -9
  8005 bytes (7.8k)
local copy
7zip -mx=9 -tgzip
  7771 bytes (7.6k)
local copy
libdeflate -12
  7755 bytes (7.6k)
local copy
pigz -11 -n
  7755 bytes (7.6k)
local copy
kzip -s0 -rn -b1
  7749 bytes (7.6k)
local copy
Zopfli
  7746 bytes (7.6k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/backbonejs/backbone-1.4.0.min.js (or via HTTPS)

You will automatically get the smallest BackboneJS 1.4.0 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 292 bytes by using my BackboneJS 1.4.0 Zopfli version instead of the best available CDN (3.77% smaller than cdnjs, 7746 vs. 8038 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 --mls64 --bsr12 --lazy --ohh

(found February 21, 2019)
Description Value Parameter
iterations 100000  --i100000
maximum blocks 8  --mb8
maximum length score 64  --mls64
block splitting recursion 12  --bsr12
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/1.4.0/backbone-min.js --location | md5sum
93a2e442d9ea4e6bfc6fe8789d7277f6  -
curl --silent --compressed https://minime.stephan-brumme.com/files/backbonejs/backbone-1.4.0.min.zopfli.js.gz | md5sum
93a2e442d9ea4e6bfc6fe8789d7277f6  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/jashkenas/backbone/1.4.0/backbone-min.js --location | sha1sum
d7a331dfccce646eb5662a18960f183bf687f49c  -
curl --silent --compressed https://minime.stephan-brumme.com/files/backbonejs/backbone-1.4.0.min.zopfli.js.gz | sha1sum
d7a331dfccce646eb5662a18960f183bf687f49c  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
unpkg 9537 bytes 93a2e442d9ea4e6bfc6fe8789d7277f6 (invalid)
Boot 8038 bytes 93a2e442d9ea4e6bfc6fe8789d7277f6 (invalid)
cdnjs 8038 bytes 93a2e442d9ea4e6bfc6fe8789d7277f6 (invalid)

Note: only the MD5 hashes are shown to keep things simple.

Other Versions

Available BackboneJS versions at minime.stephan-brumme.com:

1.4.0,
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
7746 bytes -1 byte zopfli --i100000 --mls64 --bsr12 --lazy --ohh February 21, 2019 @ 09:38
7747 bytes -1 byte zopfli --i1000 --mls128 --bsr8 --lazy --ohh February 20, 2019 @ 12:52
7748 bytes zopfli --i100 --mls4 --bsr20 --lazy --ohh February 20, 2019 @ 12:45

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

Most recent activity on February 23, 2019 @ 20:57.

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
7751 7751 7751 7751 7752 7752 7751 7751 7751 7749 7749 7749 7749 7750 7751
7748 7747 7746 7749 7747 7748 7747 7749 7747 7751 7748 7749 7752 7749 7748
7747 7747 7747 7752 7748 7751 7748 7751 7748 7750 7748 7749 7749 7748 7748
7747 7746 7747 7747 7747 7747 7746 7749 7747 7747 7748 7748 7748 7748 7753
7748 7748 7747 7748 7747 7752 7746 7749 7748 7751 7748 7749 7748 7749 7748
7747 7747 7748 7748 7749 7749 7748 7751 7748 7751 7749 7751 7748 7749 7751
7747 7747 7746 7748 7748 7748 7746 7749 7747 7751 7748 7748 7749 7749 7749
7747 7747 7747 7748 7748 7746 7747 7751 7748 7751 7748 7749 7749 7750 7749
7746 7748 7747 7752 7747 7746 7746 7749 7746 7748 7748 7749 7749 7749 7749
7746 7747 7747 7747 7747 7751 7747 7751 7748 7749 7748 7749 7748 7749 7749
7746 7746 7747 7753 7751 7747 7747 7749 7747 7751 7749 7751 7749 7749 7748
7747 7747 7747 7748 7747 7747 7747 7749 7746 7751 7748 7749 7749 7749 7748
7747 7746 7748 7747 7747 7747 7746 7749 7748 7747 7749 7753 7749 7749 7750
7747 7746 7747 7748 7747 7747 7749 7746 7746 7751 7748 7751 7749 7749 7751
7747 7746 7747 7748 7747 7747 7747 7751 7746 7751 7748 7751 7749 7749 7748
7746 7747 7747 7748 7747 7746 7747 7749 7748 7751 7748 7748 7749 7749 7748
7746 7746 7747 7752 7750 7746 7747 7749 7746 7747 7748 7751 7749 7748 7748
7746 7747 7747 7748 7747 7746 7747 7749 7746 7751 7748 7751 7749 7750 7750
7746 7746 7748 7752 7747 7747 7747 7749 7748 7751 7748 7749 7749 7749 7748
7746 7746 7746 7748 7747 7746 7746 7749 7748 7751 7748 7751 7749 7749 7748
7746 7746 7746 7747 7747 7746 7748 7749 7748 7748 7748 7749 7750 7749 7749
7747 7747 7748 7752 7747 7747 7749 7749 7751 7751 7748 7749 7750 7749 7750
7748 7747 7747 7748 7747 7747 7748 7749 7749 7747 7751 7751 7750 7749 7748

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 7748 bytes 100%
1,000 7747 bytes -1 byte 100%
10,000 7747 bytes 100%
100,000 7746 bytes -1 byte 35.94%
1,000,000 7746 bytes 12.17%
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
7749 bytes +3 bytes (+0.04%)
7749 bytes +3 bytes (+0.04%)
7778 bytes +32 bytes (+0.41%) +29 bytes
7805 bytes +59 bytes (+0.76%) +56 bytes
7834 bytes +88 bytes (+1.14%) +85 bytes
7861 bytes +115 bytes (+1.48%) +112 bytes
7870 bytes +124 bytes (+1.60%) +121 bytes
7908 bytes +162 bytes (+2.09%) +159 bytes
7936 bytes +190 bytes (+2.45%) +187 bytes

Non-DEFLATE Algorithms

Archivers based on completely different compression algorithms often produce superior results.
Unfortunately, browsers only support gzip compression at the moment.
However, support for Brotli is constantly growing - but your browser doesn't support it.
Algorithm Program Parameters Size Compared To Best Zopfli
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 6715 bytes -1031 bytes (-13.31%)
Brotli (Wikipedia) brotli brotli -q 11 7244 bytes -502 bytes (-6.48%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 7302 bytes -444 bytes (-5.73%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 7318 bytes -428 bytes (-5.53%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 7621 bytes -125 bytes (-1.61%)
Zstandard (Wikipedia) zstd zstd -19 7715 bytes -31 bytes (-0.40%)
LZMA2 (Wikipedia) xz xz -9 7748 bytes +2 bytes (+0.03%)

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 2019.
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