Certificates & Signing

Signing is the part of iOS development that confuses people the most and causes the most pitfalls. This chapter explains the relationship among Certificate → App ID (Identifier) → Device → Provisioning Profile thoroughly. Once you understand this relationship, you can locate the cause of most signing errors yourself.

What This Chapter Solves

• What is the difference between development and distribution certificates, and when do I use each?
• What is the relationship between App ID and Bundle ID, and why can’t it be changed after creation?
• What exactly is a provisioning profile? How does it relate to certificates, App IDs, and devices?
• Do I always need to register device UDIDs? Does TestFlight need them too?

Learning Goals

After finishing this chapter, you should be able to:

• Draw the “Certificate + App ID + Device → Provisioning Profile” relationship and explain why changing any element requires regenerating the profile.
• Create development/distribution certificates and back up .p12 files safely.
• Create explicit App IDs and enable the required capabilities.
• Distinguish Development, Ad Hoc, and App Store profiles.
• Debug common errors like “No valid signing certificate” and “Profile doesn’t include the device”.

Chapter Contents

Reading Suggestions

• Xcode automatic signing users: understand the principles, then let Xcode “Automatically manage signing” handle most cases — but know what it does behind the scenes.
• CI packaging teams: certificate/profile maintenance knowledge here is a prerequisite for CI signing; read carefully and combine with fastlane documentation.
• When hitting a specific error: map the error to this chapter’s “FAQs” section.