How to build an AI writing app for iOS
What an AI writing app needs
- A text editor that handles selection and replacement cleanly
- A set of templates: emails, posts, captions, summaries, outlines
- Inline actions: rewrite, shorten, expand, fix grammar, change tone
- Streamed output so results appear as they generate
- A history of past generations the user can revisit
- A backend that holds the API key and calls the model
- A usage limit so model costs stay predictable
The strongest versions pick a niche, for example marketing copy or academic writing, and tune the templates for it rather than trying to write everything.
How to build it with AppFlight
Describe it in plain English, for example: "An AI writing app with an editor, a library of templates for emails and social posts, inline rewrite, shorten, and change-tone actions on selected text, streamed results, and a history of what I generated." AppFlight plans the screens, generates native SwiftUI, and launches it in a live simulator so you can select text and run a rewrite immediately. AppFlight connects OpenAI and keeps the key as a backend secret in your own Supabase, so the app calls your backend rather than embedding the key. You iterate in plain language, for example adding a new template, a tone slider, or export to share.
Monetization for an AI writing app
Each generation has a real model cost, so monetization needs to track usage. The common model is a free tier with a word or generation cap and a subscription for unlimited or higher-volume use, sometimes sold as word credits. Add a RevenueCat paywall to manage subscriptions, and use Superwall to test paywall timing, for example after a user hits the free cap. Set your price against expected per-user model spend so heavy users stay profitable.
Shipping it to the App Store
When the app is ready, AppFlight signs the build, uploads to TestFlight, then submits to the App Store with metadata and screenshots from the simulator. If Apple rejects the build, AppFlight reads the reason, works on the fix, and resubmits. Disclose third-party AI use, get consent where required, and moderate generated content. Apple reviews every app, so a submission is not the same as an approval, but the whole pipeline runs without you opening Xcode.
FAQ
What makes an AI writing app worth paying for?
Focused templates and editing actions beat a blank prompt box. Tools like rewrite, shorten, change tone, fix grammar, and expand give people a reason to return. The model is the engine, but the templates and editing flow are the product.
How do AI writing apps make money?
A free tier with a word or generation cap, and a subscription for unlimited or higher-volume use. A RevenueCat or Superwall paywall manages it. Price to cover model costs, since each generation has a real per-call cost.
Where does the OpenAI key go?
On your backend, not in the app. AppFlight keeps the key as a backend secret in your own Supabase and has the app call your backend, which calls the model. This keeps the key out of the shipped binary.