> For the complete documentation index, see [llms.txt](https://brixxbox.gitbook.io/brixxbox-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://brixxbox.gitbook.io/brixxbox-documentation/configuration/app-editor/app-editor-properties/id.md).

# Id

The controlId is an essential part of a brixxbox Control. Every Control needs a unique (in its App) Id. All new controls get a generated Id (starting with an underscore). The generated Id is changeable but once you give your control a custom Id, this will be unchangeable afterwards. The generated Id should never be used to reference the control. If you need to do something with the control (like hide it, get or set a value), you need to give it a readable Id.

A Control is always addressed with its controlId.

Control Ids should start with a lowercase (often with a mandatory prefix, that has been set in the app) and can contain, Numbers, upper and lowercase letters and underscores.


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