Choose a version:
42% The original file has 145628 bytes (142.2k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 60441 bytes (59.0k, 42%).

After GZIP compression these minified files vary in size:
gzip -6 (default)
  16176 bytes (15.8k)
local copy
jsdelivr
  16154 bytes (15.8k)
CDN
cdnjs
  16111 bytes (15.7k)
CDN
gzip -9
  16111 bytes (15.7k)
local copy
libdeflate -12
  15611 bytes (15.2k)
local copy
7zip -mx=9 -tgzip
  15593 bytes (15.2k)
local copy
zultra
  15553 bytes (15.2k)
local copy
pigz -11 -n
  15539 bytes (15.2k)
local copy
kzip -s0 -rn -b2
  15533 bytes (15.2k)
local copy
Zopfli
  15527 bytes (15.2k)
local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-5.2.1.min.js (or via HTTPS)

You will automatically get the smallest Bootstrap 5.2.1 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 584 bytes by using my Bootstrap 5.2.1 Zopfli version instead of the best available CDN (3.76% smaller than cdnjs, 15527 vs. 16111 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 --i1000000 --mb8 --mls1024 --bsr14 --lazy --ohh

(found September 20, 2022)
Description Value Parameter
iterations 1000000  --i1000000
maximum blocks 8  --mb8
maximum length score 1024  --mls1024
block splitting recursion 14  --bsr14
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/v5.2.1/dist/js/bootstrap.min.js --location | md5sum
6a599114d93cc36d2c8e127a24a97e0a  -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-5.2.1.min.zopfli.js.gz | md5sum
6a599114d93cc36d2c8e127a24a97e0a  -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v5.2.1/dist/js/bootstrap.min.js --location | sha1sum
45be8ca0bae7e5b88244b718d4133c6aabd30cd8  -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-5.2.1.min.zopfli.js.gz | sha1sum
45be8ca0bae7e5b88244b718d4133c6aabd30cd8  -

All listed CDNs deliver identical contents:
CDN Size (compressed) MD5 (uncompressed) Timestamp
jsdelivr 16154 bytes 6a599114d93cc36d2c8e127a24a97e0a September 19, 2022 @ 14:38
cdnjs 16111 bytes 6a599114d93cc36d2c8e127a24a97e0a (invalid)

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

Other Versions

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

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
15527 bytes -1 byte zopfli --i1000000 --mls1024 --bsr14 --lazy --ohh September 20, 2022 @ 17:48
15528 bytes -1 byte zopfli --i100000 --mls4096 --bsr14 --lazy --ohh September 20, 2022 @ 11:24
15529 bytes -1 byte zopfli --i10000 --mls128 --bsr18 --lazy --ohh September 19, 2022 @ 15:56
15530 bytes -1 byte zopfli --i10000 --mls256 --bsr40 --lazy --ohh September 19, 2022 @ 15:56
15531 bytes -1 byte zopfli --i1000 --mls128 --bsr25 --lazy --ohh September 19, 2022 @ 15:20
15532 bytes -1 byte zopfli --i1000 --mls1024 --bsr40 --lazy --ohh September 19, 2022 @ 15:18
15533 bytes -1 byte zopfli --i1000 --mls4 --bsr14 --lazy --ohh September 19, 2022 @ 15:18
15534 bytes zopfli --i100 --mls4 --bsr14 --lazy --ohh September 19, 2022 @ 14:58

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

Most recent activity on September 21, 2022 @ 01:32.

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
15537 15536 15536 15536 15536 15535 15534 15536 15539 15537 15538 15538 15538 15540 15536
15536 15543 15535 15535 15542 15530 15530 15534 15534 15532 15532 15532 15538 15540 15533
15534 15534 15534 15537 15533 15539 15536 15536 15532 15534 15536 15531 15531 15534 15534
15534 15531 15536 15538 15536 15536 15534 15536 15537 15530 15531 15530 15530 15535 15531
15538 15538 15539 15538 15538 15539 15536 15537 15537 15530 15531 15531 15532 15540 15538
15533 15530 15535 15542 15539 15542 15535 15533 15537 15528 15531 15531 15538 15534 15532
15539 15530 15538 15538 15538 15531 15536 15536 15536 15530 15531 15531 15534 15533 15539
15538 15531 15539 15538 15537 15537 15529 15531 15540 15530 15533 15531 15538 15536 15531
15542 15543 15531 15542 15532 15534 15534 15536 15537 15533 15535 15535 15537 15533 15531
15539 15540 15539 15538 15538 15532 15535 15536 15532 15530 15535 15536 15532 15533 15531
15531 15531 15535 15541 15536 15535 15536 15532 15530 15527 15533 15527 15532 15538 15531
15530 15531 15538 15537 15536 15542 15536 15536 15536 15535 15534 15536 15532 15533 15540
15531 15530 15537 15538 15532 15531 15536 15531 15531 15531 15531 15531 15537 15534 15531
15534 15534 15536 15535 15533 15541 15536 15536 15530 15533 15531 15531 15531 15533 15539
15531 15531 15538 15537 15538 15533 15529 15536 15536 15536 15533 15536 15536 15534 15532
15535 15530 15535 15533 15536 15542 15536 15536 15536 15535 15531 15531 15532 15534 15531
15535 15539 15538 15538 15530 15537 15535 15536 15536 15533 15535 15535 15537 15534 15531
15532 15531 15531 15538 15538 15532 15536 15530 15538 15530 15531 15535 15531 15534 15539
15534 15535 15534 15534 15533 15542 15536 15536 15532 15532 15531 15531 15530 15534 15531
15531 15540 15531 15538 15538 15539 15529 15530 15536 15536 15536 15531 15532 15534 15531
15531 15539 15539 15534 15536 15532 15529 15536 15536 15532 15534 15535 15537 15533 15531
15533 15531 15539 15538 15532 15537 15536 15536 15531 15536 15531 15536 15537 15533 15544
15539 15540 15539 15538 15532 15533 15529 15530 15530 15529 15531 15535 15535 15534 15532

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 15534 bytes 100%
1,000 15531 bytes -3 bytes 100%
10,000 15529 bytes -2 bytes 100%
100,000 15528 bytes -1 byte 2.61%
1,000,000 15527 bytes -1 byte 0.87%
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
15628 bytes +101 bytes (+0.65%) +95 bytes
15628 bytes +101 bytes (+0.65%) +95 bytes
15533 bytes +6 bytes (+0.04%)
15563 bytes +36 bytes (+0.23%) +30 bytes
15579 bytes +52 bytes (+0.33%) +46 bytes
15604 bytes +77 bytes (+0.50%) +71 bytes
15643 bytes +116 bytes (+0.75%) +110 bytes
15642 bytes +115 bytes (+0.74%) +109 bytes
15686 bytes +159 bytes (+1.02%) +153 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 13125 bytes -2402 bytes (-15.47%)
ZPAQ (Wikipedia) zpaq zpaq -method 69 13471 bytes -2056 bytes (-13.24%)
Brotli (Wikipedia) brotli brotli -q 11 14435 bytes -1092 bytes (-7.03%)
Burrows-Wheeler transform (Wikipedia) bzip2 bzip2 -9 15224 bytes -303 bytes (-1.95%)
LZMA2 (Wikipedia) xz xz -9 15288 bytes -239 bytes (-1.54%)
Zstandard (Wikipedia) zstd zstd -19 15369 bytes -158 bytes (-1.02%)
PPMd (Wikipedia) 7zip 7za a -mx=9 -m0=ppmd 15566 bytes +39 bytes (+0.25%)

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 2022.
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.