> ## Documentation Index
> Fetch the complete documentation index at: https://docs.4mica.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Create SIWE nonce

> Create a nonce and SIWE message template for wallet authentication.

`POST /auth/nonce`

## Request body

<ParamField path="address" type="string" required>
  EVM wallet address that will sign the SIWE message.
</ParamField>

## Responses

<ResponseField name="nonce" type="string" required />

<ResponseField name="siwe" type="object" required />

<ResponseField name="siwe.domain" type="string" required />

<ResponseField name="siwe.uri" type="string" required />

<ResponseField name="siwe.chain_id" type="number" required />

<ResponseField name="siwe.statement" type="string" required />

<ResponseField name="siwe.expiration" type="string" required />

<ResponseField name="siwe.issued_at" type="string" required />

<RequestExample>
  ```bash cURL theme={null}
  curl -X POST "https://base.sepolia.api.4mica.xyz/auth/nonce" \
    -H "Content-Type: application/json" \
    -d '{"address":"0x1111111111111111111111111111111111111111"}'
  ```

  ```javascript title="Fetch" theme={null}
  const response = await fetch("https://base.sepolia.api.4mica.xyz/auth/nonce", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ address: "0x1111111111111111111111111111111111111111" }),
  });
  console.log(await response.json());
  ```

  ```javascript title="Axios" theme={null}
  import axios from "axios";
  const { data } = await axios.post(
    "https://base.sepolia.api.4mica.xyz/auth/nonce",
    { address: "0x1111111111111111111111111111111111111111" },
  );
  console.log(data);
  ```

  ```python Python theme={null}
  import requests
  url = "https://base.sepolia.api.4mica.xyz/auth/nonce"
  print(requests.post(url, json={"address": "0x1111111111111111111111111111111111111111"}).json())
  ```

  ```go Go theme={null}
  package main
  import ("bytes"; "fmt"; "io"; "net/http")
  func main() {
    body := []byte(`{"address":"0x1111111111111111111111111111111111111111"}`)
    response, _ := http.Post("https://base.sepolia.api.4mica.xyz/auth/nonce", "application/json", bytes.NewReader(body))
    defer response.Body.Close()
    result, _ := io.ReadAll(response.Body)
    fmt.Println(string(result))
  }
  ```
</RequestExample>

<ResponseExample>
  ```json 200 OK theme={null}
  {
    "nonce": "9c1c0c7e",
    "siwe": {
      "domain": "4mica.io",
      "uri": "https://4mica.io",
      "chain_id": 84532,
      "statement": "Sign in to 4Mica",
      "expiration": "2026-06-22T11:00:00Z",
      "issued_at": "2026-06-22T10:00:00Z"
    }
  }
  ```

  ```json 400 Bad Request theme={null}
  { "error": "Invalid wallet address" }
  ```
</ResponseExample>

## Status codes

| Code  | Description                               |
| ----- | ----------------------------------------- |
| `200` | Nonce and SIWE template created.          |
| `400` | The wallet address is missing or invalid. |
| `500` | The operator could not create the nonce.  |

Sign the generated SIWE message, then call
[`POST /auth/verify`](/api-reference/operator/verify-siwe).