Facebook warned it may soon stop offering a key targeted advertising tool on Apple devices, because tracking limitations set to take effect in iOS 14 were expected to cripple its effectiveness.

In a blog, the company said testing showed an inability to deliver personalised adverts could shave more than 50 per cent off revenue generated by its Audience Network system and warned publishers to prepare for this.

Depending on the extent of the damage, it “may not make sense to offer it on iOS 14” at all, Facebook stated.

Audience Network relies on device identifiers to serve personalised adverts across various non-Facebook apps and websites. In June, Apple revealed its forthcoming iOS 14 platform will require apps to secure permission to track users across other services and sites.

Facebook said it currently plans to release an updated Audience Network SDK to support iOS 14, but added it was working on a variety of other “short-and long-term strategies to support publishers through these changes”.

Apple is yet to set a launchh date for iOS 14, but Facebook executives said on its Q2 earnings in July call they expected a “pronounced impact” on advertising revenue in Q4.