September 2026

How to Open a .puz File on iPhone

Someone sends you a crossword — AirDropped, emailed, downloaded from a constructor's site — and it lands on your iPhone as a file ending in .puz. You tap it. Nothing you'd call "opening a puzzle" happens. Mail shows a generic file icon. Files might offer no app to open it with at all. It isn't broken. It's just a format iOS was never taught to read.

Why iOS doesn't know what to do with it

.puz is a small, old binary format that predates the App Store by well over a decade — it was built for Across Lite, a desktop crossword player, and it stuck around because it's simple enough that constructors, puzzle syndicates, and crossword software have kept using it ever since. iOS has no built-in reader for it, the way it has one for PDFs or images. Mail, Files, and Preview just see an unrecognized file extension and shrug.

What actually makes it work

Opening a .puz file on iPhone requires an app that has specifically registered itself as a handler for that file type. That's a real, deliberate step a developer has to take — it's what makes "Open In…" show an actual crossword app in the list instead of nothing. An app can be a perfectly good crossword solver and still not do this, if importing other people's puzzle files wasn't part of what it was built for.

A note on .ipuz

You'll also run into .ipuz files, a newer, JSON-based format designed to handle puzzle types .puz can't — cryptics, variety grids, that kind of thing. Same story applies: it only opens if the app on your phone explicitly knows how to read it.

This is exactly the gap Ultimate Crossword is being built to close — direct .puz and .ipuz import, solved fully offline, alongside a bundled archive and a built-in generator. It hasn't shipped yet, but importing your own puzzle files is a first-class feature, not an afterthought.