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

# Hash

When you're building on Polkadot, you'll often need [hashes](https://docs.polkadot.com/polkadot-protocol/parachain-basics/cryptography/#hash-functions) — to verify files, derive stable identifiers, or work with chain primitives. The `pop hash` command gives you a fast, convenient way to generate these hashes without juggling separate tools.

You can also run the command as `pop h`.

## What you can use it for

* Verify the integrity of artifacts (WASM, configs, datasets) before committing or deploying.
* Turn strings or hex into deterministic IDs for testing or scripting.
* Hash raw transaction/storage bytes when inspecting or debugging.
* Produce quick, non-cryptographic checksums during development loops.

## Quick examples

```bash
# Verify a string or small blob (cryptographic)
pop hash sha2 256 "hello world"

# Hash raw hex bytes (great for tx/storage inspection)
pop hash keccak 256 0x68656c6c6f776f726c64

# Check a runtime you are about to deploy
pop hash blake2 256 /path/to/your/file.wasm

# Append the original bytes to the hash (BLAKE2 or TwoX only)
pop hash blake2 256 --concat "hello world"
```

## Supported algorithms and lengths

| Subcommand | Alias | Lengths (bits)    | `--concat` |
| ---------- | ----- | ----------------- | ---------- |
| `blake2`   | `b2`  | 64, 128, 256, 512 | Yes        |
| `keccak`   | `kk`  | 256, 512          | No         |
| `sha2`     | `s2`  | 256               | No         |
| `twox`     | `xx`  | 64, 128, 256      | Yes        |

## Input handling

The positional `data` argument is inspected in this order:

* If it matches an existing path, Pop reads the file contents. The file must be 3 MiB or smaller.
* If it starts with `0x`, Pop parses it as hex bytes.
* Otherwise, Pop hashes the raw string bytes.

## Output

Pop prints the hash as lowercase hex without a `0x` prefix. If you use `--concat`, the output is the hash bytes followed by the original input bytes, all hex-encoded.

## Errors and constraints

* Unsupported length: `unsupported length: <length>`
* Path exists but is not a file: `specified path is not a file`
* File too large: `file size exceeds maximum code size`

## Tips

* Input can be plain text, 0x-prefixed hex, or a file path — Pop detects it for you.
* Choose the algorithm that fits the job:
  * SHA-2: dependable, broadly used.
  * BLAKE2: fast and secure (widely used in the Polkadot ecosystem).
  * Keccak: common in EVM tooling and ecosystems.
  * xxHash (TwoX): very fast, non-cryptographic for dev workflows.
* Pick an output length that matches your target (256-bit is a solid default; 512-bit for extra margin, 64/128-bit for speedier non-crypto checks).


---

# 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:

```
GET https://learn.onpop.io/chains/guides/hashing.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.