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title: Program Structure Interface (PSI)
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The Program Structure Interface, commonly referred to as just PSI, is the layer in the _IntelliJ Platform_ that is responsible for parsing files and creating the syntactic and semantic code model that powers so many of the platform's features.

* [PSI Files](/basics/architectural_overview/psi_files.md)
* [File View Providers](/basics/architectural_overview/file_view_providers.md)
* [PSI Elements](/basics/architectural_overview/psi_elements.md)

> **TIP** A very helpful tool for debugging the PSI implementation is the [PsiViewer plugin](https://plugins.jetbrains.com/plugin/227-psiviewer). 
It can show you the structure of the PSI tree, the properties of every PSI element and highlight its text range.