user121614: Today I noticed a transaction that spends a bunch of 1-of-1 multisig P2WSH inputs:
675b106c71f110ebca9e6435f49508a07b45d40d38e237d02b89e5506f3b136b
For example, the first input has this script in the witness:
OP_PUSHNUM_1
OP_PUSHBYTES_33 031f1c516fc9362202883b24fd92e6548776a8f1701baca38b63bbe635da8a82f7
OP_PUSHNUM_1
OP_CHECKMULTISIG

Why would anyone use this instead of P2WPKH which is both cheaper and has a larger anonymity set?

user5406: You may be looking at transactions of an unknown entity dubbed "Crazy1o1". To my knowledge, it is still unknown who they are or why they are using 1-of-1 transactions, but they've been active for years. Notable mentions:

LaurentMT first describing and naming Crazy1o1
LaurentMT analyzing some traffic of Crazy1o1
Stepan Snigirev asking about 1-of-1 transactions
Crazy1o1 consolidating 720k+ UTXOs at over 100 s/vB while the mempool was essentially empty
On-going traffic of 1-of-1 multisig transactions
Crazy1o1 on OXT.me

Update: LaurentMT suggests that Crazy1o1 is a “Crypto and Forex broker named KOT4X”

121614: <p>Today I noticed a transaction that spends a bunch of 1-of-1 multisig P2WSH inputs:<br />
<a href="https://mempool.space/tx/675b106c71f110ebca9e6435f49508a07b45d40d38e237d02b89e5506f3b136b" rel="noreferrer">675b106c71f110ebca9e6435f49508a07b45d40d38e237d02b89e5506f3b136b</a></p>
<p>For example, the first input has this script in the witness:</p>
<pre><code>OP_PUSHNUM_1
OP_PUSHBYTES_33 031f1c516fc9362202883b24fd92e6548776a8f1701baca38b63bbe635da8a82f7
OP_PUSHNUM_1
OP_CHECKMULTISIG
</code></pre>
<p>Why would anyone use this instead of P2WPKH which is both cheaper and has a larger anonymity set?</p>
 5406: <p>You may be looking at transactions of an unknown entity dubbed &quot;Crazy1o1&quot;. To my knowledge, it is still unknown who they are or why they are using 1-of-1 transactions, but they've been active for years. Notable mentions:</p>
<ul>
<li>LaurentMT first <a href="https://twitter.com/LaurentMT/status/1264586463536189444" rel="nofollow noreferrer">describing and naming Crazy1o1</a></li>
<li>LaurentMT analyzing some <a href="https://twitter.com/LaurentMT/status/1264958123275681793" rel="nofollow noreferrer">traffic of Crazy1o1</a></li>
<li>Stepan Snigirev <a href="https://twitter.com/StepanSnigirev/status/1413156991606865924" rel="nofollow noreferrer">asking</a> about 1-of-1 transactions</li>
<li><a href="https://twitter.com/ziggamon/status/1264233427840176129" rel="nofollow noreferrer">Crazy1o1 consolidating</a> 720k+ UTXOs at over 100 s/vB while the mempool was essentially empty</li>
<li>On-going traffic of <a href="https://mempool.observer/monitor/?filter=WD0xLW9mLTE%3D" rel="nofollow noreferrer">1-of-1 multisig transactions</a></li>
<li><a href="https://oxt.me/entity/tiid/3498542669" rel="nofollow noreferrer">Crazy1o1</a> on OXT.me</li>
</ul>
<p>Update: LaurentMT suggests that Crazy1o1 is a <a href="https://twitter.com/LaurentMT/status/1577023660153413632" rel="nofollow noreferrer">“Crypto and Forex broker named KOT4X”</a></p>
