An App ID with Identifier 'com.companyname.appname' is not available. Please enter a different string

Question

I am trying to upload my IOS app to TestFlight for beta testing. On XCode, my application's bundle ID is com.companyname.appname. When i try to create a distribution provisioning profile, i am told to create an app ID.

When i try to register an IOS App ID on the developer portal, i enter appname under App ID Description and com.companyname.appname under Bundle ID. I get the error message

There were errors in the data supplied. Please correct and re-submit.
An App ID with Identifier 'com.companyname.appname' is not available. 
Please enter a different string.

I currently have no other app with bundle ID com.companyname.appname. When i change the bundle ID to some other string like com.companyname.io, it works.

Why doesn't the bundle name com.companyname.appname work?

Should i go ahead and use a different bundle id from what is on XCode?

Am i even going about this right?

Answer 1

Are you using com.companyname.appname in your question as a placeholder for the real string you've entered in the portal, or that's really what you're using?

Bundle ID's need to be globally unique. Not just unique to you. So someone else is likely using the same com.companyname.appname as you've used.

You should be using a Bundle ID that's based on your domain name (in reverse order). For example, if your domain name is someguyfortune.com, and your app is called MyAwesomeApp, then you should use a Bundle ID of com.someguyfortune.MyAwesomeApp. Case matters. I personally prefer using all lower case letters, but Xcode will use uppercase letters by default and they work fine.

Using this reverse domain name style improves the odds that no one else will be using the same Bundle ID.

Answer 2

It most likely means there is already a bundle identifier with the same value. Bundle identifiers must be unique.