# Errors on Web

We live in an imperfect world, and sometimes things go wrong. A viewer might not be able to watch a video stream for a variety of reasons. Some example reasons are:

* The video stream is unavailable,
* The video stream is not supported on the selected platform,
* The THEOplayer license is incorrectly configured.

**When an issue occurs, an error should be triggered**.

When a fatal playback issue occurs, THEOplayer exposes information about the error through the THEOplayer API. This allows you to detect errors: as a developer, you can use an event handler to catch (and handle) `error` events. This feature (i.e. being able to intercept errors and act on it) may be mandatory to you to achieve a use-case:

* You want to log the error on an analytics stack,
* You want to show your own error message to the viewer,
* ...

THEOplayer associates error codes with errors to categorize types of issues. As a developer, these error codes may help you to log an error on an analytics stack, or may help you to generate a custom error message towards your viewer.

When a fatal playback issue occurs, THEOplayer's default UI overlays an error message on top of the video player. This error message indicates to the viewer that playback is unsuccessful.

## Related resources

* [How to do error handling](https://docs-preview.optiview.dolby.com/pr-861/theoplayer/how-to-guides/web/miscellaneous/error/error-handling.md): this article explains how you use event listeners to intercept the `error` event.
* [Error codes](https://docs-preview.optiview.dolby.com/pr-861/theoplayer/how-to-guides/web/miscellaneous/error/error-codes.md): this article explains what error codes are, and why they are useful.