> ## Documentation Index
> Fetch the complete documentation index at: https://docs.chainstack.com/llms.txt
> Use this file to discover all available pages before exploring further.

<AgentInstructions>

## Submitting Feedback

If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback:

POST https://docs.chainstack.com/feedback

```json
{
  "path": "/reference/arbitrum-debug-preimage",
  "feedback": "Description of the issue"
}
```

Only submit feedback when you have something specific and actionable to report.

</AgentInstructions>

# debug_preimage | Arbitrum

Arbitrum API method that returns the preimage for a given Keccak-256 hash. In Ethereum's state trie, account addresses are stored as their Keccak-256 hashes. This method allows retrieving the original data (preimage) that was hashed. The node must have preimage recording enabled for this method to return results.

<Note>
  Learn how to [deploy a node](/docs/debug-and-trace-apis#arbitrum) with the debug and trace API methods enabled.
</Note>

<Warning>
  This method is available for post-Nitro blocks only (block 22,207,815 and later). For pre-Nitro blocks, use the `arbtrace_*` methods instead.
</Warning>

<Warning>
  Preimage recording must be enabled on the node (`--cache.preimages`). If preimages are not stored, this method returns an error.
</Warning>

<Check>
  **Get your own node endpoint today**

  [Start for free](https://console.chainstack.com/) and get your app to production levels immediately. No credit card required.

  You can sign up with your GitHub, X, Google, or Microsoft account.
</Check>

## Parameters

* `hash` — the Keccak-256 hash to look up the preimage for, encoded as a hex string.

## Response

* `data` — the raw preimage bytes as a hex string. Returns an error if the preimage is not found.

## `debug_preimage` code examples

<CodeGroup>
  ```javascript ethers.js theme={"system"}
  const ethers = require('ethers');
  const NODE_URL = "YOUR_CHAINSTACK_ENDPOINT";
  const provider = new ethers.JsonRpcProvider(NODE_URL);

  const debugPreimage = async (hash) => {
    const result = await provider.send("debug_preimage", [hash]);
    console.log(result);
  };

  debugPreimage("0x0000000000000000000000000000000000000000000000000000000000000000");
  ```

  ```python web3.py theme={"system"}
  from web3 import Web3
  node_url = "YOUR_CHAINSTACK_ENDPOINT"
  web3 = Web3(Web3.HTTPProvider(node_url))

  hash_value = "0x0000000000000000000000000000000000000000000000000000000000000000"
  result = web3.provider.make_request('debug_preimage', [hash_value])
  print(result)
  ```
</CodeGroup>

## Use case

The `debug_preimage` method is useful for resolving Keccak-256 hashes back to their original values. In the state trie, account addresses and storage keys are stored as hashes. This method allows developers building state analysis tools to reverse-lookup hashes to their original addresses or data, which is essential for tools like state diff visualizers and trie explorers.


## OpenAPI

````yaml /openapi/arbitrum_node_api/debug_and_trace/debug_preimage.json POST /66f812de2a6724a75a51f60dd6f2a154
openapi: 3.0.0
info:
  title: Chainstack Node API
  version: 1.0.6
  description: >-
    This is an API for interacting with a Chainstack node using the
    debug_preimage method.
servers:
  - url: https://nd-954-882-037.p2pify.com
security: []
paths:
  /66f812de2a6724a75a51f60dd6f2a154:
    post:
      tags:
        - upload
      summary: debug_preimage
      operationId: debugPreimage
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                id:
                  type: integer
                  default: 1
                jsonrpc:
                  type: string
                  default: '2.0'
                method:
                  type: string
                  default: debug_preimage
                params:
                  type: array
                  items:
                    type: string
                    title: Hash
                    description: The Keccak-256 hash to look up the preimage for.
                  default:
                    - >-
                      0x0000000000000000000000000000000000000000000000000000000000000000
      responses:
        '200':
          description: Returns the preimage for the given hash.
          content:
            application/json:
              schema:
                type: object
                properties:
                  jsonrpc:
                    type: string
                  id:
                    type: integer
                  result:
                    type: string

````