# URL Parameters URL Parameters is a built-in Data Source in Appfarm for adding variables to be used as parameters of your App url. The use case for this is typical to maintain some App State when e.g. the App is refreshed. A good example of this is when you have selected a Project from a list of Projects, and navigated to the Project Details view: You would like that same Project to be selected and displayed when you refresh the page. Adding a URL Parameter for holding the selected Project ID solves this. ### Video You may see a video on URL Parameters below. {% embed url="" %} A video on URL Parameters {% endembed %} ### Documentation Relevant articles in our documentation: [URL Parameters](/how-to/enhance-your-app/deep-links.md) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.appfarm.io/appcademy/appfarm-fundamentals/app-data-fundamentals/url-parameters.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.