On Android, a "handler" is just an app registered to open certain links (like http:// , mailto: , or tel: ). Firefox for Android can handle links, PDFs, and other files. There's no separate "Firefox Handler APK."
If an app name sounds odd ("Handler APK"), check official sources first. The real Firefox handles links just fine. Don’t let a confusing name trick you into downloading something dangerous. Bottom line for you: There is no legitimate "Firefox Handler APK" from Mozilla. Only download Firefox for Android from the Google Play Store or Mozilla’s official website. That app will handle links, PDFs, and other files automatically once you set it as default. Firefox Handler Apk
Let me clear this up with a short, helpful story. The Misunderstood Download On Android, a "handler" is just an app
But Alex paused and asked: What is a handler? The real Firefox handles links just fine