# Introduction to conversion helpers

Conversion helpers are functions that let you define how custom HTML markup is converted between the model and the view, without writing low-level converters.

The editor supports a vast amount of the most commonly used HTML elements via [existing editor features](../../../../features/index.md) out-of-the-box. If your aim is to easily enable common HTML features that are not explicitly supported by the dedicated CKEditor 5 features, use the [General HTML Support feature](../../../../features/html/general-html-support.md).

There are, however, cases where you might want to provide a rich editing experience for a custom HTML markup. The conversion helpers are the way to achieve that. Read the following guides to learn how to use them.

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## Helpers by category

* **[Downcast helpers – model to view conversion](downcast.md)**

* **[Upcast helpers – view to model conversion](upcast.md)**

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Full index of the CKEditor 5 documentation: [llms.txt](../../../../../llms.txt)