There are several ways you can export and build mobile apps from Construct 3. This tutorial outlines the various options, and links to other tutorials to explain each option in more detail.
Developing for mobile
While developing for mobile, the quickest way to test on a mobile device is with the Remote Preview feature.
You may also want to check the tutorials Supporting multiple screen sizes and using touch controls.
Exporting for mobile
When you export your project, you can choose the Android or iOS options. Each platform has different build options.
Android build options
We recommend building Android apps using Construct 3's mobile app build service. See the tutorial Building Android apps (APKs) in Construct 3. If you are a new user, or aren't sure which option to use, start with this.
The other options include:
iOS build options
To publish an iOS app, Apple require that you use Xcode on macOS. They also have stringent requirements on how apps are tested and signed. Because of this, Construct's export options for iOS ultimately produce an Xcode project, where you then continue testing or publishing with Apple's tools.
We recommend choosing the Xcode project build option for iOS. This will directly give you the Xcode project to work with on a Mac. For more information, see the tutorial iOS application development and publishing with Xcode.
You can also use the Cordova project option. This can be submitted to third-party build services like PhoneGap Build (which can directly build a .ipa file for your iOS app, if you provide it with the necessary information).
Advanced users can also use the Cordova project option to run manual builds with the Cordova CLI. For more information see the tutorial Building mobile apps locally with Cordova CLI. However if you are not on a Mac, all you can build is an Xcode project, in which case you may as well choose the Xcode project build option instead.