Apple and Google are fierce competitors when it comes to phones, digital assistants and map apps. But they get along quite amicably when it comes to Apple's iCloud service.

In its latest iOS Security document, a detailed explanation of the technology choices it makes to keep you from getting hacked, Apple disclosed it's using Google's cloud-computing infrastructure to store iCloud data like photos, files and data backup. CNBC spotted the change Monday.

iCloud uses "third-party storage services, such as [Amazon] S3 and Google Cloud Platform" to store iCloud data after it's been broken into chunks and encrypted. Previously, Apple called out its use of Microsoft's Azure along with Amazon's cloud-computing service. 

Apple didn't respond to a request for comment about why it made the change or whether Microsoft's competing service is still part of the mix.

Don't expect Google Maps to reclaim its previous status as the iPhone's mapping service, or for Google's YouTube app to ship with iPhones as it once did. But it appears that Apple is willing to do business with Google when it makes sense now.

That's quite a turnaround. When phones powered by Google's Android software appeared on the market, Apple co-founder and then-CEO Steve Jobs was famously outraged by their similarity to Apple's competing iOS. "I'm going to destroy Android, because it's a stolen product. I'm willing to go thermonuclear on this," Jobs declared. 

Google is in a distant third place after Amazon and Microsoft when it comes to cloud-computing services that let customers like Apple or Netflix tap into global pools of computing resources. Google's cloud business now brings in more than $1 billion per quarter, and other customers include bank HSBC and payment services company PayPal, according to Diane Greene, who runs the division.

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