Why does a Wi-Fi tag work on Android but not on iPhone?
The iPhone reads the record perfectly well and does not act on it, because joining a network from a tag is not something iOS offers. No change to how the tag is written alters this, which means the solution is a second route for iPhone users rather than a better tag.
The tag is not broken
This is worth establishing first, because a great deal of time is wasted rewriting a tag that was correct all along.
Read the tag with a tool on the same iPhone. The Wi-Fi record appears, with its network name and its fields, exactly as written. The read succeeded, the record is valid, and the phone simply has no behaviour attached to it.
Nothing about the record type, the tag family, the writing tool or the order of records changes this outcome.
Why the platforms differ
Android attaches system behaviour to a wider set of record types than iOS does. Apple restricts what a tag may trigger, and network configuration is one of the things it does not hand to an unauthenticated object on a wall.
That is a defensible position rather than an oversight. A tag anyone can write, that any passer by can tap, offering to join a network is a mechanism with obvious abuse potential.
Apple documents what Core NFC supports rather than what it declines, so the compatibility picture is established by testing rather than by reading a list of exclusions.
What actually works instead
A QR code. Both platforms join a network from a scanned Wi-Fi QR code, and generating one is free. Printed beside the tag, it covers the audience the tag misses.
A printed password, which is unglamorous and never fails.
A URL record pointing at a page with instructions, which works on both platforms and gives you somewhere to explain. It does not join the network for the visitor, and it does turn a dead tap into a useful one.
Deploying for a mixed audience
Assume half your visitors have iPhones and design accordingly. A tag with no visible alternative reads as broken to those people, and a broken tag damages trust in the whole arrangement.
The arrangement that works in practice is a small printed card carrying a QR code and the tag inside it, with a line of text saying to tap or scan. Neither audience is excluded and neither has to know why.
If only one route is possible, choose the QR code. It reaches everyone, and the tap is the enhancement rather than the mechanism.
Frequently asked questions
Will a future iOS version add this?
Unknowable, and not something to build on. Design for what the platform does today, and treat any later improvement as a bonus rather than a plan.
Can an app on iPhone join a network from a tag?
Applications are constrained in what they may do with network configuration, and a general purpose NFC tool cannot offer this. The reliable route remains a QR code.
Does adding a second record help?
Only as a fallback with a different purpose, such as a URL pointing at instructions. It does not make the Wi-Fi record work, since a record iOS ignores stays ignored.
Is this the only record type with this problem?
No, it is the most commonly encountered one. Application launching records behave differently across platforms too, which is why testing on both devices is part of the writing procedure rather than an afterthought.