How to Open Application Using Url

How to launch an application using a URL link from a web page?

this is named Uniform Resource Identifier (aka URI).

The beginning of your URL "yourapp" would be a scheme. There are some schemes which are much used, for example ftp:, file:, mailto:, tel:, git:.

There are a lot of it but the support is very limited and as you said, depends on the browser and what software the client has installed on it. So, the scheme has nothing to do with the OS when you use a predefined scheme. If you want to have your own application you need to tell the OS "Uhm, hi there, could you please listen to that scheme" (As example in Windows with the Registry). And you can't do that from the browser because that would open a lot of possible attacks from the browser to your OS.

So to answer your questions: The right one for every OS? Is this universal? Yes, You need only one scheme, as it does not depend on the OS.

Think about it: What do you want to archive? A mailto:? Just do it. A ftp:? Well, your client has to have a FTP-Client with URI-Support. A custom app, like myapp:? That's a lot of work and I wish you good luck with that as it is a custom program for every OS.

If interested, see this link for a list of all schemes.

I hope, I could help you. Have a nice day :)

How can I launch my windows app when a users opens a url?

You have to designate custom protocol name unused by any other app like for example "myapp".

Then bind your application to this protocol.

Then url like myapp://myname.com/users/edit/5 will open your application (and pass the URL to the application for further processing).

How to launch an application from a browser?

You can't really "launch an application" in the true sense. You can as you indicated ask the user to open a document (ie a PDF) and windows will attempt to use the default app for that file type. Many applications have a way to do this.

For example you can save RDP connections as a .rdp file. Putting a link on your site to something like this should allow the user to launch right into an RDP session:

<a href="MyServer1.rdp">Server 1</a>

How to launch application from web browser on Windows and macOS?

Custom URI Scheme will help you to achieve this for your app.
For eg: zoommtg, zoomus schemes are used by Zoom
example: Windows/Mac client: zoommtg://zoom.us/join?confno=123456789&pwd=xxxx&zc=0&browser=chrome&uname=Betty

iOS/Android Client: zoomus://zoom.us/join?confno=123456789&pwd=xxxx&zc=0&browser=chrome&uname=Betty

Ref:
https://medium.com/zoom-developer-blog/zoom-url-schemes-748b95fd9205

How to open an Url using In-App Browser from a flutter application from a button click?

What you are looking for is called a Webview.

Look at https://pub.dev/packages/webview_flutter

How can I use a link on my website to open an application?

If you mean opening a desktop application in response to a web page, you can use a custom application protocol but that is browser- and OS-specific.