Bluesky uses an iOS privacy API to stamp its logo on screenshots

A developer noticed that screenshots of Bluesky posts show the Bluesky logo where the app itself displays a "Follow" button, and tracked the mechanism down in the app's publicly available source.

The relevant code sits in a file named GrowthHack.tsx, added in January 2026 by the developer mozzius, which depends on a package by the same author called expo-privacy-sensitive. According to the post, the package creates a UITextField with isSecureTextEntry set to true and renders the real content — the Follow button — into that field's .layer. When iOS takes a screenshot, it blanks the layer to protect secure text input, and the logo underneath becomes visible. On non-iOS platforms, the package renders content normally with no masking.

The author also found the trick fails if you screenshot mid-app-switch, when the Follow button does appear. Their explanation is a guess, stated as such: iOS captures its own snapshot at the start of the gesture without triggering the blanking, so there is no live text field left to react. They note twice they are not an iOS developer.

For anyone shipping mobile apps, the practical takeaway is that this is a documented-enough pattern to be durable. The post says Telegram used the same approach for secret chats and so did Signal, which is the author's reason for doubting Apple will close it. Whether repurposing a privacy API for brand watermarking is acceptable is contested — the post says most commenters on the pull request adding the behavior disliked it, and the thread was locked.