# Custom error handlers

Besides customizing the error page, you can also customize how all errors are handled and override the default system behavior.

For example, the default <mark style="color:red;">`‘Page Not Found’`</mark> error would navigate to the <mark style="color:red;">`/error`</mark> page but if you would rather show a toaster alert, the following could be added to the <mark style="color:red;">`App`</mark> model.

```json
{
	"errorHandlers": [{
        "actions": [{
            "action": "showAlert",
            "function": "action.options.text = action.options.error.message",
            "options": {
                "text": "",
                "title": "Error",
                "type": "error"
            }
        }],
        "codes": ["404"]
    }]
}
```

As it can be seen above, custom behaviours are added under a reserved global actions key <mark style="color:red;">`errorHandlers`</mark>, and that will be an array of objects. Each object having have <mark style="color:red;">`codes`</mark> and <mark style="color:red;">`actions`</mark>.

| Key     | Value                                                                                             |
| ------- | ------------------------------------------------------------------------------------------------- |
| codes   | <mark style="color:red;">`array`</mark> of error codes that the associated actions will run with. |
| actions | array of actions                                                                                  |

The result from the example code above is the alert shown below.

<figure><img src="/files/0mwor88b2I4itkl3ggOF" alt=""><figcaption></figcaption></figure>

The error data can be found under <mark style="color:red;">`options`</mark> for each action of the array, for a given code. The error object has the same shape as previously presented [here](/engineering-reference-docs/betterforms-error-pages-api/custom-error-pages.md) and can be accessed as follows:

| Key                                           | Path                              |
| --------------------------------------------- | --------------------------------- |
| <mark style="color:red;">`code`</mark>        | actions.options.error.code        |
| <mark style="color:red;">`description`</mark> | actions.options.error.description |
| <mark style="color:red;">`message`</mark>     | actions.options.error.message     |


---

# Agent Instructions: 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://docs.klai.studio/engineering-reference-docs/betterforms-error-pages-api/custom-error-handlers.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.