What is an Android app signature file? Why can't I modify it?

A signature is a verification mechanism for Android apps in the Android system. It describes the trust relationship between the developer and an app. Typically, the system verifies whether the new app version has the same signature as the installed app when you upgrade the app. If they are inconsistent, the new version cannot be installed. After an app is launched, we do not recommend that you change the app signature. Most third-party services, such as Google Maps and Amap, verify the app's developer information based on the fingerprint information of the signature. Therefore, modifying the signature may also affect third-party services.