Choose a version:
42% The original file has 144701 bytes (141.3k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 60104 bytes (58.7k, 42%).

After GZIP compression these minified files vary in size:
unpkg
  23476 bytes (22.9k)
 CDN
gzip -6 (default)
  16092 bytes (15.7k)
 local copy
jsdelivr
  16072 bytes (15.7k)
 CDN
cdnjs
  16028 bytes (15.7k)
 CDN
gzip -9
  16024 bytes (15.6k)
 local copy
libdeflate -12
  15538 bytes (15.2k)
 local copy
7zip -mx=9 -tgzip
  15524 bytes (15.2k)
 local copy
zultra
  15485 bytes (15.1k)
 local copy
pigz -11 -n
  15463 bytes (15.1k)
 local copy
kzip -s0 -rn -b2
  15462 bytes (15.1k)
 local copy
Zopfli
  15450 bytes (15.1k)
 local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-5.2.0.min.js (or via HTTPS)

You will automatically get the smallest Bootstrap 5.2.0 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 578 bytes by using my Bootstrap 5.2.0 Zopfli version instead of the best available CDN (3.74% smaller than cdnjs, 15450 vs. 16028 bytes):
Download
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 --mls2048 --bsr10 --lazy --ohh

(found August 1, 2022)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 2048  --mls2048
block splitting recursion 10  --bsr10
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/twbs/bootstrap/v5.2.0/dist/js/bootstrap.min.js --location | md5sum
e6f488c5766fb06169100bdbd2b4fdbd  -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-5.2.0.min.zopfli.js.gz | md5sum
e6f488c5766fb06169100bdbd2b4fdbd  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v5.2.0/dist/js/bootstrap.min.js --location | sha1sum
f7365985962f78092d8eeaca6d6633d6fbf75583  -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-5.2.0.min.zopfli.js.gz | sha1sum
f7365985962f78092d8eeaca6d6633d6fbf75583  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
unpkg 23476 bytes e6f488c5766fb06169100bdbd2b4fdbd (invalid)
jsdelivr 16072 bytes e6f488c5766fb06169100bdbd2b4fdbd July 29, 2022 @ 14:38
cdnjs 16028 bytes e6f488c5766fb06169100bdbd2b4fdbd (invalid)

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

Other Versions

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

5.2.3, 5.2.2, 5.2.1, 5.2.0,
5.1.3, 5.1.2, 5.1.1, 5.1.0,
5.0.2, 5.0.1, 5.0.0,
4.6.0,
4.5.3, 4.5.2, 4.5.1, 4.5.0,
4.4.1, 4.4.0,
4.3.1, 4.3.0,
4.2.1, 4.2.0,
4.1.3, 4.1.2, 4.1.1, 4.1.0, 4.0.0,
3.4.1, 3.4.0,
3.3.7, 3.3.6, 3.3.5, 3.3.4, 3.3.2, 3.3.1, 3.3.0,
3.2.0,
3.1.1, 3.1.0,
3.0.3, 3.0.2, 3.0.1, 3.0.0

The project site contains an overview how well these versions were compressed.
Other interesting projects are AngularJS, BackboneJS, D3, Dojo, Ember, jQuery, Knockout, lodash, React, Socket.IO, ThreeJS, UnderscoreJS and Vue.

Changelog

Best Zopfli parameters so far:
Size Improvement Parameters Found
15450 bytes -1 byte zopfli --i1000000 --mls2048 --bsr10 --lazy --ohh August 1, 2022 @ 09:27
15451 bytes -1 byte zopfli --i100000 --mls2048 --bsr10 --lazy --ohh July 29, 2022 @ 19:34
15452 bytes -2 bytes zopfli --i10000 --mls2048 --bsr10 --lazy --ohh July 29, 2022 @ 16:23
15454 bytes -1 byte zopfli --i10000 --mls128 --bsr11 --lazy --ohh July 29, 2022 @ 16:23
15455 bytes -1 byte zopfli --i1000 --mls1024 --bsr14 --lazy --ohh July 29, 2022 @ 15:36
15456 bytes -1 byte zopfli --i1000 --mls64 --bsr7 --lazy --ohh July 29, 2022 @ 15:36
15457 bytes -1 byte zopfli --i1000 --mls32768 --bsr16 --lazy --ohh July 29, 2022 @ 15:36
15458 bytes – zopfli --i100 --mls1024 --bsr9 --lazy --ohh July 29, 2022 @ 15:00

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

Most recent activity on August 1, 2022 @ 19:09.

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
2 15461 15460 15460 15460 15460 15460 15460 15459 15464 15462 15462 15464 15463 15465 15473
4 15460 15462 15464 15462 15463 15460 15463 15461 15458 15454 15455 15457 15457 15457 15457
6 15468 15462 15464 15465 15468 15464 15462 15470 15461 15463 15459 15460 15455 15457 15456
7 15468 15455 15463 15460 15459 15454 15462 15462 15454 15454 15456 15454 15457 15457 15456
8 15463 15457 15462 15463 15459 15458 15462 15461 15459 15464 15459 15459 15456 15465 15456
9 15466 15455 15466 15466 15462 15467 15462 15457 15466 15452 15457 15457 15454 15457 15457
10 15464 15455 15463 15462 15463 15458 15454 15461 15461 15460 15450 15455 15457 15458 15459
11 15454 15463 15463 15462 15463 15462 15454 15454 15465 15455 15459 15455 15462 15458 15455
12 15468 15466 15467 15465 15456 15467 15462 15461 15466 15457 15462 15460 15459 15460 15463
13 15458 15450 15463 15462 15462 15463 15452 15462 15461 15454 15458 15458 15457 15457 15463
14 15466 15455 15464 15466 15457 15461 15460 15460 15455 15452 15452 15454 15455 15457 15457
15 15455 15464 15463 15462 15462 15466 15460 15461 15462 15462 15459 15459 15457 15457 15455
16 15455 15455 15462 15462 15463 15457 15462 15461 15457 15452 15455 15455 15457 15457 15452
17 15466 15464 15470 15466 15462 15465 15461 15460 15454 15461 15455 15455 15455 15457 15459
18 15455 15463 15463 15462 15457 15462 15451 15460 15450 15454 15459 15458 15460 15458 15456
19 15465 15462 15466 15465 15467 15469 15462 15461 15460 15454 15454 15454 15455 15458 15455
20 15455 15462 15462 15463 15459 15462 15460 15460 15451 15460 15458 15459 15456 15458 15456
21 15456 15456 15469 15462 15463 15462 15454 15461 15450 15455 15454 15457 15455 15457 15462
22 15465 15456 15462 15466 15457 15457 15462 15461 15466 15464 15454 15455 15455 15457 15462
23 15455 15455 15463 15463 15463 15463 15454 15454 15455 15465 15459 15455 15456 15457 15457
25 15466 15455 15463 15463 15462 15457 15460 15454 15454 15462 15459 15459 15456 15457 15459
30 15463 15455 15455 15463 15459 15463 15454 15460 15454 15454 15458 15458 15456 15457 15463
40 15460 15463 15455 15462 15463 15462 15454 15454 15466 15461 15451 15455 15454 15458 15454

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 15458 bytes – 100%
1,000 15455 bytes -3 bytes 100%
10,000 15452 bytes -3 bytes 100%
100,000 15451 bytes -1 byte 3.77%
1,000,000 15450 bytes -1 byte 2.03%
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
(any) 15553 bytes +103 bytes (+0.67%) +91 bytes
1 15550 bytes +100 bytes (+0.65%) +88 bytes
2 15462 bytes +12 bytes (+0.08%) –
3 15488 bytes +38 bytes (+0.25%) +26 bytes
4 15507 bytes +57 bytes (+0.37%) +45 bytes
5 15531 bytes +81 bytes (+0.52%) +69 bytes
6 15564 bytes +114 bytes (+0.74%) +102 bytes
7 15569 bytes +119 bytes (+0.77%) +107 bytes
8 15610 bytes +160 bytes (+1.04%) +148 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 - for example, your browser actually supports it !
Algorithm Program Parameters Size Compared To Best Zopfli
RAR (proprietary) RAR rar a -m5 -md64m -mc63:128t -mt1 13057 bytes -2393 bytes (-15.49%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 13420 bytes -2030 bytes (-13.14%)
Brotli (Wikipedia) brotli brotli -q 11 14370 bytes -1080 bytes (-6.99%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 15136 bytes -314 bytes (-2.03%)
LZMA2 (Wikipedia) xz xz -9 15216 bytes -234 bytes (-1.51%)
Zstandard (Wikipedia) zstd zstd -19 15292 bytes -158 bytes (-1.02%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 15461 bytes +11 bytes (+0.07%)

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):
Load and Parse Data


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 2026.
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

All trademarks are property of their respective owners. You know, the boring legal stuff.