Apple yesterday published detailed guidelines for developers of web browser apps and email clients who wish to be considered as the new default app options in iOS 14 and iPadOS 14.

The company previously stated that it was working with select developers of popular iOS email clients and web browsers as launch partners for when the feature goes live publicly later this fall. And while early screenshots and simulations have shown that the feature will work as advertised, the new guidelines cast more light on some of the limitations and requirements.

For instance, default browser apps must feature a URL field or provide search tools for finding relevant links or include curated lists of bookmarks. When opening a URL, these app must navigate directly to the specified destination and render the expected web content.

“Apps that redirect to unexpected locations or render content not specified in the destination’s source code don’t meet the requirements of a default web browser,” Apple notes.

Browser apps designed to operate in a parental controls or locked down mode may restrict navigation to comply with those goals. Third-party browsers are permitted to warn user if they’re about to visit content suspected of phishing or other problems.

As for third-party email apps, those are required to fully support sending or receiving messages to and from any valid email recipients or senders. Apps that provide user-controlled incoming mail screening features are permitted as well.

Early screenshots have revealed how setting default apps might work.

When the user has a web browser installed on their device, a new Default Browser App option appears in Settings and the user is able to change their default web browser from Safari to a compatible third-party app (same with email clients).

Third-party apps work as full Safari and Mail replacements and the user is warned that their websites or email addresses will be opened in another app the first time they make the change.