> For the complete documentation index, see [llms.txt](https://developers-apps-in-toss.toss.im/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers-apps-in-toss.toss.im/documentation/api-and-sdk-en/sdk/domains-api/tossauth/tossauth.sign.md).

# TossAuth.sign

> Functional API `appsInTossSignTossCert`You can use the same function with this as well.

### Feature description

Sign using a Toss certificate. `txId`is the Transaction ID used for identity verification, simple authentication, and electronic signatures with a Toss certificate.

Toss app Android/iOS `5.233.0` It can be used in versions at or above this one. If called in an unsupported version, `UNSUPPORTED_APP_VERSION` an error occurs.

### Type

```ts
TossAuth.sign(params: AppsInTossSignTossCertParams): Promise<void>;
```

**Params**

```ts
type AppsInTossSignTossCertParams = {
  txId: string;
};
```

**Response**

None

### Error code

The error code is the `error.code` value.

| Code                      | Description                                                                                                                                                                                                                         |
| ------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `UNSUPPORTED_APP_VERSION` | If the running Toss app version does not support this feature, it occurs immediately upon calling. `TossAuth.sign.isSupported()`Check in advance with, and if it occurs `error.message`show the user the (update guidance message). |

### Example code

```js
import { TossAuth } from "@apps-in-toss/web-framework";

const button = document.querySelector("#sign-button");

button.addEventListener("click", async () => {
  try {
    await TossAuth.sign({ txId: "f2e1a6df..." });
  } catch (error) {
    console.error(error);
  }
});
```


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