How to use tel: with * (star, asterisk) or # (hash, pound) on iOS?

I'm trying to initiate a call on the iPhone with the tel url that has a * in it. It properly brings up the call dialog but drops back to safari w开发者_开发百科hen you click call.

<a href="tel:123*12">Test</a>

This documentation from Apple should be helpful:

To prevent users from maliciously redirecting phone calls or changing the behavior of a phone or account, the Phone application supports most, but not all, of the special characters in the tel scheme. Specifically, if a URL contains the * or # characters, the Phone application does not attempt to dial the corresponding phone number.

UPDATE (Jan 2, 2018): The information mentioned here may be outdated. Please refer to new documentation if Apple has relaxed these rules in their newer SDKs. Refer to Husam's answer.

iOS11 now allows us to call number with * or #

Swift Example code

    let number = "*111*12345#"
    let app = UIApplication.shared
    if let encoded = number.addingPercentEncoding(withAllowedCharacters: .urlHostAllowed) {
        let u = "tel://\(encoded)"
        if let url = URL(string:u) {
            if app.canOpenURL(url) {
                app.open(url, options: [:], completionHandler: { (finished) in

                })
                return
            }
        }
    }

The approved answer is not correct, at least anymore. I've tested both as a web page and in app being able to dial using the special character # and *. What you do have to do if you wish to use those characters in either instance though is to encode them.

In HTML, # becomes %23 and * does not need to be escaped

If using Swift, you can encode your link and press it from an app using this function:

//number format example (commas are pauses): 123-456-7890,,555#,1234
fileprivate func callNumber(_ number: String) {
    let dialString = "telprompt://" + number
    if let escapedDialString = dialString.addingPercentEncoding(withAllowedCharacters: .urlHostAllowed) {
      if let dialURL = URL(string: escapedDialString) {
        UIApplication.shared.openURL(dialURL)
      }
    }
  }

If you want to add * to href typed as "tel" you need to use the utf-8 encoded version - %2A

Reference : W3

For example

<a href="tel:%2A1234"> Phone me <a/>