A document published by Apple has confirmed rumors that the company’s iCloud service is using Google’s cloud storage.

The latest version of the iOS Security Guide, published in January, lists Google Cloud Platform as the potential destination for users’ data alongside AWS, reports CNBC. At the same time, any mention of Microsoft’s Azure cloud service is gone.

It was widely known that iCloud relied on S3 storage from AWS, but until now, Apple’s dealings with Google were mostly a subject of speculation.

A cloud within a cloud

“iCloud stores a user’s contacts, calendars, photos, documents, and more and keeps the information up to date across all of their devices, automatically. iCloud can also be used by third-party apps to store and sync documents as well as key values for app data as defined by the developer,” states the Security Guide.

“The encrypted chunks of the file are stored, without any user-identifying information, using third party storage services, such as S3 and Google Cloud Platform.”

It’s not clear whether this is an indication that the company is moving away from Microsoft as its cloud provider – but it’s the first time Apple has aknowledged that it relies on services provided by Google, one of its biggest competitors, especially in the mobile device market.