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# System Fields

In addition to the fields that are defined through the Data Model there are a lot of fields that come directly from Lektor. They can be easily recognized because they are prefixed by a leading underscore (`_`).

These fields influence how Lektor treats pages and attachment. Here we will just go over the most important ones but for a full list you can have a look at the API Documentation.

## `_hidden`

This field is a boolean value and controls if a page is hidden or not. If a page is hidden all of its children will automatically also be hidden. A page that is hidden will not be processed by Lektor's build system. This means such pages can be discovered through the query API but they are not rendered themselves. This is useful for situations where you want to have information stored but not rendered. This is for instance used to implement Single-Page websites.

To read more read the field documentation.

## `_discoverable`

This fields in many ways is similar to `_hidden` but instead makes a page be only hidden from queries. In particular this means that it will still be processed and built, but that it becomes harder for code to reference it. Pages that are not set to discoverable can only be found through queries if they are explicitly included.

This field was added in Lektor 2.0. In earlier versions this feature is unavailable.

To read more read the field documentation.

## `_model`

This key sets the Data Model that is used for the record. If not set this defaults to one of different choices depending on configuration or name. Parent models can pre-define the model for children, which is then used if this key is not set. If not set this will be picked up by an algorithm. See Default Model Selection for more information.

To learn more read the field documentation.

## `_slug`

This field can override the default URL slug. For more information about this feature see URLs and Slugs.

## `_template`

This field can be used to override the default template selection which is just the model name with the `.html` extension.

To learn more read the field documentation.

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