> For the complete documentation index, see [llms.txt](https://hub.bsvblockchain.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hub.bsvblockchain.org/wiki/transactions-and-utxos/bitcoin-transactions/sighash-flags.md).

# SIGHASH flags

**SIGHASH flags** are a byte appended to an ECDSA signature in a Bitcoin transaction input that specify which parts of the transaction's inputs and outputs the signature covers. Because the flag controls what a signature actually commits to, different flags allow the same signature scheme to support different transaction construction patterns, such as multi-party contracts, crowdfunding-style transactions, and payment channels. There are three base flags, which can be combined with the ANYONECANPAY modifier:

* **SIGHASH\_ALL (0x01)** - the default. Signs all of the transaction's inputs and outputs. Any change to any input or output after signing invalidates the signature.
* **SIGHASH\_NONE (0x02)** - signs all of the transaction's inputs, but none of the outputs. Outputs can be changed or added after signing without invalidating the signature.
* **SIGHASH\_SINGLE (0x03)** - signs all of the transaction's inputs and only the output at the same index as the input being signed. Other outputs can be changed or added after signing.
* **SIGHASH\_ANYONECANPAY (0x80)** - a modifier that can be combined with any of the above (e.g. SIGHASH\_SINGLE|ANYONECANPAY) to sign only the specific input being signed, rather than all inputs. This allows other parties to add their own inputs to the transaction after signing. In all cases, the input script (scriptSig) of the input being signed is always excluded from the signed message, regardless of which SIGHASH flags are used - see Transaction Malleability for why this matters. For details of how these flags are applied during signature hash calculation, see Legacy Sighash Algorithm.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://hub.bsvblockchain.org/wiki/transactions-and-utxos/bitcoin-transactions/sighash-flags.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.