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![EliBenSasson Avatar](https://lunarcrush.com/gi/w:24/cr:twitter::884309808274341888.png) Eli Ben-Sasson | Starknet.io [@EliBenSasson](/creator/twitter/EliBenSasson) on x 41K followers
Created: 2025-07-23 14:09:25 UTC

What's OP_CAT and why do I care about it?

Bitcoin's computer is a bit like a clunky scientific calculator, the kind used in high school. Each button is called an "op_code." And from time to time, the Bitcoin community may agree on adding a new button.

OP_CAT is one such potential button. Satoshi added it, then removed it, back in the day.

What OP_CAT does is something pretty simple: it joins together two strings of characters, like "copy-paste", so it's a pretty simple and safe button. But if you add it to the scientific calculator that is Bitcoin, suddenly you allow Bitcoin's computer to verify ZK-STARKs and other proof systems. It opens the way to rollups and massive scale, in a self-custodial way that stays true to Bitcoin's and Satoshi's principles.

I'm XXX% sure Satoshi isn't around. If s/he were, s/he’d have had OP_CAT (and many other op_codes) on Bitcoin long, long ago.


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**Related Topics**
[satoshi](/topic/satoshi)
[opcat](/topic/opcat)
[bitcoin](/topic/bitcoin)
[coins layer 1](/topic/coins-layer-1)
[coins bitcoin ecosystem](/topic/coins-bitcoin-ecosystem)
[coins pow](/topic/coins-pow)

[Post Link](https://x.com/EliBenSasson/status/1948022644156104891)