Undocumented and subject to change

Worth understanding before building anything permanent on top of these mechanisms, including our own service.

6 August 2026 · PAD team

What this depends on

Only one row in that table is properly documented, and it is the one on the platform where the problem barely exists.

The most recent change

In iOS 26 some Facebook builds stopped adding FBAV and FBAN to the user agent. No announcement, no changelog entry, no error anywhere. Detection code written before that quietly started classifying Facebook traffic as Safari.

Anyone who had built this once and moved on was misrouting traffic for as long as it took them to notice, which for most people is never.

What this means for building it yourself

The eighty lines of routing code are not the work. The work is noticing when one of the mechanisms above changes, which requires measuring arrival rate continuously rather than testing once.

What it means for buying it

Ask a vendor what they did during the iOS 26 change. If the answer is that customers had to do nothing, that is the actual product: not the redirect, but keeping up with five undocumented mechanisms owned by three companies.

Honest caveat about us

We are subject to the same conditions. Our escape routes work today and could stop working with any app release. What we can promise is measurement: when a route stops working, the arrival rate moves and we see it within a day.