# callbacks.onExternalLink

Part of [Callbacks](https://kernstra.com/docs/web-sdk/config/callbacks) in the Kernstra Web SDK 1.0.0 configuration reference.

- Type: `(url: string) => void`
- Page: https://kernstra.com/docs/web-sdk/config/callbacks/onexternallink

Takes over web, `mailto:` and `tel:` links in the document. Receives only addresses that passed the SDK's scheme check: `http:`, `https:`, `mailto:` and `tel:` (an address written without a scheme arrives with `https://` in front). `javascript:`, `data:` and every other scheme never reach it, in-document links still jump to their page, and [`links.confirmExternal`](https://kernstra.com/docs/web-sdk/config/links/confirmexternal) no longer applies. The address is chosen by whoever wrote the document, so show it to the user before opening it, and open it with `noopener,noreferrer`. An exception thrown by your handler is logged with `console.error`.

Web page: https://kernstra.com/docs/web-sdk/config/callbacks/onexternallink