What freezing iOS User-Agent means for device detection
Apple Freezes User-Agent Strings
Apple’s iOS 26 freezes the User-Agent string reported by the company’s Safari browser.
Prior to the launch of iOS 26, User-Agent strings accurately reported the version of iOS that Safari was running on.
From September 2025 that’s no longer the case.
When Safari is run on a device with iOS 26 installed, it instead reports the OS version as 18.6.
The following User-Agent string is being returned from iOS 26 running Safari. Notice the OS version 18.6 is incorrect.
Mozilla/5.0 (iPhone; CPU iPhone OS 18_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.0 Mobile/15E148 Safari/604.1
This discrepancy was originally noted during the beta phase of iOS 26 and was expected to be rectified at the time of release.
However, that expectation has been proven wrong. The release notes for Safari 26.0 confirming that the frozen OS version is an intentional change by Apple.
So, what next for device detection?
Up until October 1st 2025, 51Degrees will be reporting the version as Apple provide it. If an iPhone is running Safari 26.0 on iOS 26, it will be reported as 18.6.
After October 1st 2025, iPhones reporting iOS 18.6 running on Safari 26.0 will return 26. The majority of iOS devices will have been updated within two weeks of launch.
For those working with the Browser profile ID they will observe this will change for the same User-Agent evidence.
The change doesn't impact Chrome or browsers based on Chromium running on iOS.
We will continue to monitor Apple's position and our user's feedback.
Why has Apple made this change?
This change is an example of Apple’s policy of signal reduction and is aligned with their longstanding practice of degrading interoperability.
Apple is removing information from the market while retaining it for themselves. We will be evaluating the competition implications.