Do you have a form where you ask a user to enter a website URL ?
There is no direct way to validate URL in PowerApps today, however, you can use IsMatch function along with Regular Expressions to do this.
Here is the expression you need to validate a URL –
IsMatch(URL_Input.Text, "(?:http(s)?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#[\]@!\$&'\(\)\*\+,;=.]+$")
That’s it, now you can use this to change the border-color of the Text Input box so that the app user knows when he URL entered is incorrect.
Here is an example –

The expression that is used in the border color property –
If(!IsBlank(URL_Input.Text), If(IsMatch(URL_Input.Text, "(?:http(s)?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#[\]@!\$&'\(\)\*\+,;=.]"),Green,Red),RGBA(166, 166, 166, 1))
Hope this helped.
Don’t forget to follow the blog to get the latest content on Power Platform.
Also, you can follow me on Twitter and subscribe to my channel on YouTube .
This doesn’t work if the URL has /folder/subfolder/etc. This one works (from https://www.regextester.com/94502)
(?:http(s)?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#[\]@!\$&’\(\)\*\+,;=.]+$
Thank you for pointing that out. I have updated the blog post. 🙂