> For the complete documentation index, see [llms.txt](https://docs.fractalbitcoin.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fractalbitcoin.io/faqs.md).

# FAQs

📍 **Q: How does Fractal prevent against replaying transactions to BTC nodes?**

A: Fractal is not a Bitcoin fork and does not use Bitcoin's UTXO set. Therefore, any transaction within a Fractal block cannot be included on the Bitcoin chain. The main concern isn't transaction replay, but rather protecting against malicious websites attempting to use Bitcoin mainnet UTXOs to trick Fractal wallets into signing unauthorized transactions.

***

**📍 Q: OP\_CAT has been enabled in previous forks, but no significant new use cases emerged. Why would Fractal Bitcoin be different?**

A: Times have changed. Back then, all opcodes were available, and there was no space constraint, so developers had little motivation to explore "how far we can go with only OP\_CAT." Today, with the support of SegWit and Taproot in the current Bitcoin Core versions, scripts can be more controlled and isolated, allowing for the creation of more flexible business logic.

Soon, you'll see the first use case on Fractal: staking and voting mechanisms based on Bitcoin scripts and implemented with OP\_CAT. This solution avoids the limitations of time-locks (enabling free staking and unlocking) and works without relying on third-party oracles. It’s a technical feat that cannot be achieved on Bitcoin mainnet today, but with OP\_CAT, we can accomplish it easily. An unlocking transaction has a vsize of around 340 bytes.

🔗 [Check out the transaction example here](https://mempool-testnet.fractalbitcoin.io/zh/tx/947cb90ac33b2523977422cc373d948a51e93f035a2bc677856c932bc5ab1098)