# heynavid

> Navid is an indie iOS developer based in the Netherlands building small, privacy-respecting apps on his own. heynavid.com is his personal site: his App Store apps, notes on how they get built, and an independent hub for building apps for iPhone Duo, Apple's foldable iPhone.

Principles behind the apps: charge once instead of renting software back monthly, do the work on-device rather than on a server, and ship no ads and no advertising or ad-tracking SDKs. Each app stays close to a real problem, so they are focused utilities rather than broad platforms.

## Core pages
- [Home](https://heynavid.com/): Navid and a few featured apps.
- [Apps](https://heynavid.com/apps/): All 10 iOS apps, with descriptions, plus the ones coming soon.
- [About](https://heynavid.com/about/): Who Navid is, his approach, and how to reach him.
- [Blog](https://heynavid.com/blog/): Notes on building and shipping the apps.

## iPhone Duo

Independent notes and a developer reference for iPhone Duo, written by an iOS developer building apps for it. Not affiliated with Apple. Facts checked against Apple's pages and the iOS 27.1 SDK on 2026-09-26.

- What is iPhone Duo? iPhone Duo is a foldable iPhone from Apple, announced on 9 September 2026. It has a 7.6-inch inner display that folds, and a 5.4-inch outer display for using it closed like a normal phone.
- When can you buy iPhone Duo? Pre-orders open on Friday 16 October 2026. It is available from Friday 23 October 2026 in the first countries, with more regions from Friday 30 October.
- Do existing iPhone apps work on iPhone Duo? Yes. An app built with the iOS 26 SDK or earlier runs at a familiar size and aspect ratio when the device is open. Rebuilt with the iOS 27.1 SDK, it runs edge to edge on the inner display with regular width, like an iPad.
- What makes an app an iPhone Duo app? The parts only this phone has: poses like book and tabletop, where the fold splits the inner screen, the hinge as an input, and the outer screen facing the person being filmed while the camera runs. The bigger screen alone does not count, because every app rebuilt with the current SDK gets it.
- Which apps support iPhone Duo? Apple named Netflix, Zoom and Slack at launch. From heynavid, Fold Cue is a teleprompter that shows your script on the outer screen beside the main camera, planned for 23 October 2026, and ComicFlow gets a book pose with the fold as the gutter of a two-page spread in version 3.5. The directory at heynavid.com/duo/apps/ lists each app with where its claim comes from.
- Is this site affiliated with Apple? No. heynavid is the independent site of Navid, an indie iOS developer. iPhone Duo is a trademark of Apple Inc.
- What is the iPhone Duo screen size in points? The inner display is 669 × 951 points in portrait at @3x, with regular width. The outer display is 466 × 678 points at @3x, with compact width. Lay out in points and read sizes from your scene or view, never from UIScreen.main.
- What screenshot sizes does the App Store use for iPhone Duo? Inner display: 2007 × 2853 pixels, or 2853 × 2007 in landscape. Outer display: 1398 × 2034 pixels, or 2034 × 1398. App Store Connect does not accept screenshots for this device yet.
- How do I read the iPhone Duo hinge angle? In SwiftUI use .onHingeChange, and in UIKit add a UIHingeInteraction. Both give a status of closed, partially open or fully open, plus a continuous angle. Apple makes no promise about how often the angle updates, so do not depend on a frequency or a precision.
- How do I keep content out of the fold on iPhone Duo? Query the fold as a reserved region with reservedRegions(kind: .division) from a GeometryProxy in SwiftUI or from a UIView in UIKit. It is only active when the device is partly open. ArrangementView in SwiftUI and UIArrangementViewController in UIKit place two views either side of it.
- Can an app show its own content on iPhone Duo's outer screen? Only while it is using the camera. Register a camera capture accessory with CameraCaptureAccessory in SwiftUI or UISceneAccessory.cameraCapture in UIKit. It can appear while the app is in the foreground with a capture session and a visible preview, the device is open and the app is full screen on the inner display. Apps cannot open other windows on the outer display.
- Which Xcode and SDK do I need for iPhone Duo? Xcode 27.1 beta with the iOS 27.1 SDK. It includes the iPhone Duo simulator, which runs in Device Hub. Builds made with it can go to internal and external TestFlight testing.

- [iPhone Duo hub](https://heynavid.com/duo/): What Navid is building for iPhone Duo, and notes from building it.
- [iPhone Duo for developers](https://heynavid.com/duo/developers/): Display sizes in points and pixels, the hinge and fold APIs, the outer screen rule, cameras, SDK behaviour and the simulator. Checked 2026-09-26.
- [Apps for iPhone Duo](https://heynavid.com/duo/apps/): A curated directory of apps for iPhone Duo: Navid's own, plus the apps Apple named at launch (5 listed).
- [Designing Fold Cue around an outer screen I can't test yet](https://heynavid.com/blog/designing-for-an-outer-screen-i-cant-test/): Fold Cue's best feature on iPhone Duo is the script on the outer screen, beside the camera. The system decides when that screen is mine, and I won't hold a Duo until it goes on sale. So the app is designed to be fine without it.
- [What Fold Cue would never cut, and what it isn't trying to be](https://heynavid.com/blog/what-fold-cue-would-never-cut/): Fold Cue was planned in a hurry, for a phone that isn't out yet. The most useful part of the plan wasn't the feature list. It was deciding in advance what would never be traded away when time ran short, and what the app wasn't going to try to be.
- [I'm building apps for a phone I haven't held yet](https://heynavid.com/blog/building-for-a-phone-i-havent-held/): iPhone Duo isn't in anyone's hands yet, and I'm already building for it. Why now, what makes an app a Duo app rather than a big phone app, and the kinds of app I've decided not to build.
- [The lines that made ComicFlow assume every iPhone was the same shape](https://heynavid.com/blog/comicflow-assumed-every-iphone-was-the-same-shape/): Running ComicFlow in the iPhone Duo simulator showed stretched layouts, phone-sized covers and a reader that decided on spreads by orientation. The Duo exposed them, but several of the bugs were already shipping on iPad.
- [The iPhone Duo's inner screen is drawn larger than its panel](https://heynavid.com/blog/iphone-duo-inner-screen-drawn-larger/): The simulator, App Store Connect and Apple's spec sheet give different pixel sizes for the iPhone Duo's inner display. None of them is wrong. The simplest explanation is that the system renders larger than the panel and scales down, which is one more reason to lay out in points.
- [On iPhone Duo, the outer screen belongs to apps using the camera](https://heynavid.com/blog/iphone-duo-outer-screen-camera-only/): Third-party apps can show interactive content on the iPhone Duo's outer screen while they run on the inner one, but only through a camera capture accessory. That one rule decides which Duo ideas are possible, and it closed off a few I wanted to build.
- [Reading the hinge on iPhone Duo, and designing around what Apple won't promise](https://heynavid.com/blog/reading-the-iphone-duo-hinge/): iOS 27.1 gives every app the iPhone Duo's hinge status and a live angle, with no entitlement. The API is small. The interesting part is the one promise Apple leaves out, and how to design an interaction that doesn't need it.
- [Setting up the iPhone Duo simulator, and the things that tripped me up](https://heynavid.com/blog/setting-up-the-iphone-duo-simulator/): The iPhone Duo simulator ships in the Xcode 27.1 beta. Getting it running took one surprise from xip, a renamed Simulator app, a permission error on my external drive, a noisy first boot, and screenshots that came out black.
- [iPhone Duo RSS feed](https://heynavid.com/duo/rss.xml): Full text of every iPhone Duo post.

## Apps
- [Fold Cue](https://heynavid.com/apps/foldcue/): Teleprompter That Follows Your Voice. A teleprompter that records you. The script follows your voice and waits when you stop, and on iPhone Duo it faces you on the outer screen. (Photo & Video, Free + Pro unlock, not released yet. Planned for 23 October 2026, the day iPhone Duo goes on sale)
- [Solspot](https://heynavid.com/apps/solspot/): Plant light meter. Measure how much light a spot in your home really gets, then see which houseplants will live there. Free, offline, no account. (Utilities, Free)
- [ComicFlow](https://heynavid.com/apps/comicflow/): Read, convert & organize comics. Read CBR, CBZ, and PDF comics, convert them, and send them to your e-reader. Offline, one-time price, no account. (Utilities, $2.99)
- [PhotoStrip](https://heynavid.com/apps/photostrip/): Batch photo toolkit. Resize, convert, compress, and strip metadata from hundreds of photos at once. Free for small batches, one payment for the rest. (Photo & Video, Free + $4.99 unlock)
- [Nava](https://heynavid.com/apps/nava/): Sleep & focus sounds. White, pink, and brown noise with nature sounds and binaural beats, all generated on-device. No subscription. (Health & Fitness, $2.99)
- [Negink](https://heynavid.com/apps/negink/): AI tattoo maker & body preview. Describe a tattoo idea and get artwork in 20 styles, then see it on your own arm before you book. Three free designs, no account. (Graphics & Design, Free + credit packs)
- [Wallora](https://heynavid.com/apps/wallora/): AI painting art. Generate wall art in 25 painting styles and preview it in a real room before you print it. (Graphics & Design, Free + subscription)
- [DiceCraft](https://heynavid.com/apps/dicecraft/): Board game roller. Animated 3D dice for any tabletop game. Seven dice types, six game presets, shake to roll, no ads. (Games, $0.99)
- [Mino](https://heynavid.com/apps/mino/): PDF compressor & merger. Shrinks PDFs by up to 90%, merges documents, and splits out pages. Nothing gets uploaded. (Productivity, $2.99)
- [PlotCraft](https://heynavid.com/apps/plotcraft/): Graphing calculator. Plot equations on an interactive canvas with 20+ functions. A small, fast graphing tool. (Education, $0.99)
- [Timeflip](https://heynavid.com/apps/timeflip/): Mirror clock puzzle. A small brain game: read the real time from a mirrored analog clock. Free, no ads, trains spatial reasoning. (Games, Free)

## Writing
- [Designing Fold Cue around an outer screen I can't test yet](https://heynavid.com/blog/designing-for-an-outer-screen-i-cant-test/): Fold Cue's best feature on iPhone Duo is the script on the outer screen, beside the camera. The system decides when that screen is mine, and I won't hold a Duo until it goes on sale. So the app is designed to be fine without it.
- [Following a voice through a script, on the device](https://heynavid.com/blog/following-a-voice-through-a-script/): Fold Cue's script scrolls as you speak and waits when you stop. The hard part isn't hearing the words. It's deciding where in the script the speaker is right now, and never guessing out loud.
- [Takes that survive a phone call, and captions spelled the way you wrote them](https://heynavid.com/blog/takes-that-survive-a-phone-call/): Fold Cue records with an asset writer rather than the simple movie output, feeds the same microphone audio to the recording and to speech recognition, and keeps everything on one clock. That one decision is what makes crash-safe takes, trimmed commands and script-perfect captions possible.
- [The teleprompter text that cost more than the camera](https://heynavid.com/blog/teleprompter-text-cost-more-than-the-camera/): Fold Cue froze for seconds every time I rotated my phone. Two of the causes were visible in the code without any tools. The biggest one only showed up in a trace: the scrolling script was being redrawn on the main thread, over and over.
- [What Fold Cue would never cut, and what it isn't trying to be](https://heynavid.com/blog/what-fold-cue-would-never-cut/): Fold Cue was planned in a hurry, for a phone that isn't out yet. The most useful part of the plan wasn't the feature list. It was deciding in advance what would never be traded away when time ran short, and what the app wasn't going to try to be.
- [I'm building apps for a phone I haven't held yet](https://heynavid.com/blog/building-for-a-phone-i-havent-held/): iPhone Duo isn't in anyone's hands yet, and I'm already building for it. Why now, what makes an app a Duo app rather than a big phone app, and the kinds of app I've decided not to build.
- [The lines that made ComicFlow assume every iPhone was the same shape](https://heynavid.com/blog/comicflow-assumed-every-iphone-was-the-same-shape/): Running ComicFlow in the iPhone Duo simulator showed stretched layouts, phone-sized covers and a reader that decided on spreads by orientation. The Duo exposed them, but several of the bugs were already shipping on iPad.
- [The iPhone Duo's inner screen is drawn larger than its panel](https://heynavid.com/blog/iphone-duo-inner-screen-drawn-larger/): The simulator, App Store Connect and Apple's spec sheet give different pixel sizes for the iPhone Duo's inner display. None of them is wrong. The simplest explanation is that the system renders larger than the panel and scales down, which is one more reason to lay out in points.
- [On iPhone Duo, the outer screen belongs to apps using the camera](https://heynavid.com/blog/iphone-duo-outer-screen-camera-only/): Third-party apps can show interactive content on the iPhone Duo's outer screen while they run on the inner one, but only through a camera capture accessory. That one rule decides which Duo ideas are possible, and it closed off a few I wanted to build.
- [Reading the hinge on iPhone Duo, and designing around what Apple won't promise](https://heynavid.com/blog/reading-the-iphone-duo-hinge/): iOS 27.1 gives every app the iPhone Duo's hinge status and a live angle, with no entitlement. The API is small. The interesting part is the one promise Apple leaves out, and how to design an interaction that doesn't need it.
- [Setting up the iPhone Duo simulator, and the things that tripped me up](https://heynavid.com/blog/setting-up-the-iphone-duo-simulator/): The iPhone Duo simulator ships in the Xcode 27.1 beta. Getting it running took one surprise from xip, a renamed Simulator app, a permission error on my external drive, a noisy first boot, and screenshots that came out black.
- [The Bug I Was Certain I Had, and the Six I Actually Had](https://heynavid.com/blog/the-bug-i-was-certain-i-had/): ComicFlow 3.4 was finished when a paying reader said a comic would not open. I was sure the cause was RAR5. It was six mundane things wearing the same blank page, because one catch block had been swallowing every error since the reader's first commit.
- [A One-Star Review, and the Eight Bytes That Fixed It](https://heynavid.com/blog/mislabelled-comic-archives/): A reader said ComicFlow didn't recognise 90% of his comic files. He was right, and every one of those files was fine. I was routing archives by their filename instead of reading what was actually inside them.
- [Measuring Light With an iPhone, and Admitting How Wrong It Might Be](https://heynavid.com/blog/honest-light-measurement-iphone/): iOS won't give third-party apps the ambient light sensor. You can derive lux from the camera's exposure metering instead, but the number is soft. Building Solspot was mostly about what to do with that.
- [Nine Apps, Five Different StoreKit Shapes](https://heynavid.com/blog/storekit-product-types-ten-apps/): Paid up front, paid plus an unlock, free plus an unlock, free plus consumable credits, free plus a subscription. What each one costs you in code, and the one I removed after shipping it.
- [Three of My Apps Had the Wrong Price on My Own Website](https://heynavid.com/blog/wrong-price-on-my-own-website/): Mino was listed as free while charging $2.99. Timeflip charged $0.99 while being free. Nobody noticed for months, because nothing was comparing the pages to the store. Here's the 150 lines that now do.
- [ComicFlow 3.0: Send Comics to Your E-Reader, Lock Private Shelves, and Free CBZ Export](https://heynavid.com/blog/comicflow-3-release/): ComicFlow 3.0 adds EPUB export for Kobo, Boox and reMarkable, Face ID-locked collections, reader presets, and free CBZ export. Still one-time, still offline, still no subscription.
- [Why I Built ComicFlow (And What I Learned Shipping a Niche iOS App)](https://heynavid.com/blog/why-i-built-comicflow/): I'm an indie iOS dev. I shipped a comic reader to a market dominated by Panels and Shonen Jump. Here are the unsexy decisions that made it work, and the mistakes I made along the way.

## Optional
- [llms-full.txt](https://heynavid.com/llms-full.txt): The full text of every post and the iPhone Duo answers in one file.
- [RSS feed](https://heynavid.com/rss.xml): Every post, full text.

## Contact
- Email: hello@heynavid.com