HTML Input autocomplete not working in WKWebview

I know I'm late to the party, but I had a surprisingly hard time finding a solution to such an old problem, so I wanted to share since this is still high on the Google results.

The autofill that I wanted was for the WKWebView to autocomplete a saved username and password for easy login. However, this could present a security risk to the user, so you have to add the "Associated Domains" entitlement to the iOS app that tells it which domains/subdomains it can trust, and you have to add a JSON file to the web site server's wwwroot/.well-known directory to prove that you control the site you are displaying in the WKWebView. Once that is done, then the username/password is autosuggested the same way that it is in Safari.

Here is the Apple documentation: https://developer.apple.com/documentation/xcode/supporting-associated-domains

To summarize the steps I took, in XCode, I went to the "Signing and Capabilities" tab in my app target, clicked the "+ Capability" button, added Associated Domains, and put entries in the newly created list for all of my subdomains:

webcredentials:example.com
webcredentials:www.example.com
webcredentials:othersubdomain.example.com

And then on my web server, I added a file to the .well-known directory called "apple-app-site-association" (no extension) with the following contents:

{
  "webcredentials": {
    "apps": [ "ABCDE12345.com.example.myapp" ]
  }
}

(where the format for the identifier is <Application Identifier Prefix>.<Bundle Identifier>). Then I browsed to https://www.example.com/.well-known/apple-app-site-association to make sure that the json was displayed in the browser.

Note: I use ASP.Net Core MVC, and the file WASN'T displayed in the browser since it doesn't use a recognized file extension. I found several methods for getting around that - I chose to add a file extension to the file and then use a rewrite rule in startup.cs so that Apple can find the file without supplying the extension in the request. You can find more on that at asp.net core - How to serve static file with no extension

https://developer.apple.com/documentation/security/password_autofill/enabling_password_autofill_on_an_html_input_element?language=objc

Try using the below format to get html autofilling your fields

<input id="user-text-field" type="email" autocomplete="username"/>