Stuck in App Review
Missing review notes, unexplained permissions, an internal app sent for public release. Each rejection costs days. We prepare for review from day one.
Build iOS Native apps with Swift
Diffco builds iPhone and iPad apps in Swift and SwiftUI: consumer apps, internal tools for your staff, and apps that talk to hardware. We also take over existing apps. Senior engineers set the architecture; AI agents build within it; a person tests every key flow on real devices before release and before every update going to production.
Senior engineers. Native Swift by default. App Store submissions handled end to end.
Products we developed are used by
Awards and client reviews
- Top AI Development Company
- Top 10 Software Developers
- Top AI Developers
in California
- Top Software Development Company
Diffco turned our concept into a polished product from scratch, delivering on a tight timeline. Clear communication, organized project management, and a strong mix of creativity and technical expertise produced an app that exceeded our vision.
Mason MeninCo-founder at WYA Group, Inc.Their commitment to excellence ensures our platform remains robust and adaptable to our evolving needs. With their expertise, we've successfully enhanced our offerings, making our collaboration highly effective.
Pete GualfettiHead of Design and Integration at Good2GoWe were impressed by Diffco's approach to the development process and how they engineer new solutions. They look ahead, learn about your product and strategy, and develop sophisticated, highly functional solutions.
Stas TushinskiyCEO & Co-founder at InstreamaticDiffco supplied us with the skilled engineers we needed to meet our ambitious goals. Their account manager proactively addressed concerns, ensuring our expectations were met.
Razvan SpatariuSenior Software Engineering Manager at MultiverseDiffco took on a complex financial system build for us — the kind of work that touches fund accounting and compliance, where there’s no margin for error — and they delivered. They helped us shape our AI product strategy rather than just executing tickets. Real ownership of the outcome.
Adam HooksCEO at Vero K12Diffco handled discovery for two complex health tech AI products for us. They’re technically sharp, honest about what’s actually worth building, and easy to work with. They moved fast without cutting corners and understood the healthcare space. Highly recommend.
Mark MagazuPrincipal at M3 Veterinary Innovation AdvisorsDiffco's expertise and engineering approach increase the reliability and efficiency of our IoT infrastructure. Diffco has proven to be a reliable partner with exceptional expertise. I highly recommend their services.
David C ThompsonSenior Digital Initiatives director at ChemTreatThe quality and consistency of the team make Diffco stand out from other vendors.
Art DanielovCEO at FlashgridThey were communicative, consultative, and helpful. They went above and beyond all the way. What an amazing team. I will work with them again and again.
Don MarklandCEO at Accountability Now
Where iOS apps go wrong
A demo runs on one iPhone.
A product runs on every iPhone your customers own.
Most iOS problems skip the demo. They show up in App Review, on real devices and networks, in the next iOS release, and when the team moves on.
Privacy details filled in last
Privacy manifests, tracking prompts and App Store labels written the night before submission. We map every data flow before the build.
Crashes nobody can reproduce
A crash on an older iPhone, a memory spike in a long session, no logs. We add crash reporting and test on the oldest iOS you support.
Offline as an afterthought
It works in the office and fails in a basement or on a plane, and sync overwrites what users typed. So we design offline and sync before the screens.
Concurrency debt that comes due
Completion handlers, shared mutable state, warnings switched off. Swift 6 mode turns them into errors. We move one module at a time, and the app keeps shipping.
The team that built it is gone
No documentation, no tests, and the signing certificates expire next month. We start with an audit and get the build working again.
From demo to product, on real phones
Every key flow is tested on real devices, on weak networks and on the oldest iOS version you support, before submission, not after the first one-star review. App Review is a checklist we work to from day one.
iOS app development services
From a first iPhone app to a tool your team relies on
New iPhone and iPad apps
Native apps in Swift and SwiftUI, from design through TestFlight to App Store release, with the architecture and data model decided in discovery.
Best for:Founders and product teams launching on iOS first.
Internal and enterprise apps
Sales, field and operations apps for your staff, connected to your systems and shipped through the right Apple channel: unlisted, custom or in-house.
Best for:Companies putting a tool in employees’ hands.
Apps that talk to hardware
Bluetooth and Wi-Fi device apps, low-latency audio and video streaming, and companion apps for connected products, where milliseconds matter.
Best for:IoT, audio and consumer-hardware companies.
Takeovers and modernization
Apps another team left behind: faults reproduced before they’re fixed, builds and certificates recovered, Objective-C moved to Swift where it pays.
Best for:Products whose original team is gone.
AI features on iPhone
On-device AI with Apple’s Foundation Models framework, App Intents and Core ML, camera and voice features, and cloud models where needed.
Best for:Apps adding AI that has to be fast and private.
Choosing the approach
Native Swift, React Native or Flutter?
React NativeFlutterNative Swift
Best whenBoth platforms, a React teamOne codebase, a custom-drawn UI
iOS is core, or the app leans on Apple hardware
iOS is core, or the app leans on Apple hardwareNew Apple APIsVia native modules, after a lagVia plugins, after a lagAvailable on release day
Available on release dayLook and feelNative componentsFlutter-drawn widgetsExactly what iOS users expect
Exactly what iOS users expectPerformanceGood for most appsGood for most appsBest for graphics, audio, video and hardware
Best for graphics, audio, video and hardwareAndroid✓ Same codebase✓ Same codebaseA separate app, or shared code via Kotlin Multiplatform
A separate app, or shared code via Kotlin MultiplatformTypical riskNative-module upkeepBigger binaries; new features arrive laterTwo apps to fund if you need Android
Two apps to fund if you need AndroidWe build all three, and we’ll recommend cross-platform when you need Android on the same date and budget.
How we build
Senior engineers decide the architecture. AI agents build the app. A person tests it on real devices.
Our own AI delivery platform puts your plan, your design system and your iOS rules in front of every agent before it starts: the oldest iOS version you support, which data stays on the device, what App Review requires. It checks everything it produces on every change.
Senior engineers decide what to build and how; more than 100 AI agents per engineer build inside those rules around the clock. Before release, a person runs each key flow on real iPhones and iPads, on weak networks and older iOS versions, and signs off against a standard agreed before the code existed.
The loop, on an iOS app
- You say what the app must do, and what must never happen
- We show the screens, data and permissions it touches
- You approve a clickable prototype before it’s built for real
- Agents build inside the plan, with a check on every change
- A person tests it on real devices and signs off; then TestFlight, then the App Store
- 100+AI agents per engineer, directed by senior engineers
- Every changechecked against the plan, the tests and Apple’s review rules
- One planscreens, data and permissions agreed before the build
- 3 monthsfrom an idea to WYA’s MVP on the App Store
What you get
An app your users trust and your next developer can read
Native feel, built in
SwiftUI and UIKit each used where they fit, with Dynamic Type, VoiceOver and dark mode handled: the details iOS users notice when they’re missing.
Releases without drama
Automated builds, code signing and TestFlight distribution, with App Review notes and privacy details prepared for every submission.
Crashes you can see and fix
Crash reporting, performance monitoring and logs from real devices, with alerts that fire before your ratings move.
Code and accounts in your name
The Swift codebase, tests, certificates and App Store Connect access in your name, plus the plan, rules and decision log as plain files in your repo.
Why teams choose Diffco for iOS
Engineers who have shipped to the App Store, not just the simulator
We’ve taken over a live, top-rated app
When Happier Meditation’s team changed, we took over its iOS and Android apps, kept them running and handled App Store releases end to end.
We’ve built the internal sales app
NanaWall’s iPad app lets its sales team present projects, products and specifications to clients, alongside a web app for those clients.
We’ve built apps that talk to hardware
Clovitek’s TV audio over Wi-Fi and iSeeU’s in-car video both needed a custom low-latency protocol. We built the protocol and the apps.
We go from idea to App Store fast
WYA’s native iOS MVP reached the App Store within three months of the idea. The speed comes from deciding early, not from cutting review.
We plan for App Review from day one
Review notes, demo accounts, privacy details and the right distribution channel are settled before the first submission, not the night before.
Senior team, in your time zone
The engineer who designs your app’s architecture is the engineer who ships it.
Engineering takeover · Consumer
Keeping a top-rated meditation app shipping through a team change
Happier Meditation, formerly Ten Percent Happier, runs native iOS and Android apps on a Rails back end. Through a major organizational transition, Diffco took over engineering, kept the top-rated app running and handled App Store submissions end to end.
- 4.8★App Store rating
- Uninterrupteda top-rated app kept running through the team change
- End to endApp Store submissions handled by Diffco
Two ways to start
Audit the app you have, or hand us the build.
iOS app audit
One to two weeks. A senior iOS architect, with agents reading the codebase, crash reports and release setup, reviews architecture, performance, privacy and App Review readiness, then delivers ranked fixes with an estimate given as a range.
Fixed price, agreed up front- Covers code, crashes, certificates and App Store Connect setup
- The report is yours. Use it with any team, including your own
Build with Diffco
Discovery in a few days to two weeks; a clickable prototype within the first weeks; TestFlight builds soon after. Senior engineers decide, agents build inside the plan, a person signs off on real devices. Monthly team allocation or a fixed scope after discovery.
- Estimate given as a range with its open questions
- Apple developer account and certificates in your name from day one
- Handover with runbooks and a codebase you can read
What we bring
Our iOS stack, from Swift to the back end
Language and UI
Swift
SwiftUI
UIKit
Objective-C- Swift Concurrency
Combine
Apple frameworks
SwiftData
Core Data
CloudKit
StoreKit
HealthKit
Core Bluetooth
AVFoundation
MapKit
On-device AI
Foundation Models
Core ML
Vision
Speech
Release and quality
Xcode
XCTest
Swift Testing
TestFlight
Xcode Cloud
Fastlane
Crashlytics
Sentry
Back end and services
Node.js
Firebase
Stripe
OpenAI
Anthropic
Our case studies
In-car child-monitoring iOS app with ultra-low-latency streaming, from technical investigation to launch in two months
TV audio over Wi-Fi, a task another team hadn’t solved: firmware, protocol, and iOS and Android apps
Native mobile social app for nights out with a curated venue catalog and venue rewards
Custom face tracking and morphing for an iOS movie-parody app, 0.04s detection
Native mobile restaurant-matching app with taste-based AI and 1,000+ curated venues
Explore our
amazing case studies
Let’s build something
great together.
Frequently Asked Questions
Because the hard parts are decided first: architecture, offline behavior, privacy and App Review. Senior engineers set the plan; AI agents build inside it; a person tests every key flow on real devices before release. That’s how an app survives its first iOS update and its first thousand users.
Native Swift when iOS is central to the business, when you depend on Apple hardware or new APIs, or when performance is the product. React Native or Flutter when one codebase for both platforms matters more. We recommend in discovery and write the reason down.
Yes, end to end: developer account setup, certificates, TestFlight, review notes, privacy details and responses to App Review. For Happier Meditation, we handled App Store submissions end to end.
Yes. We start with an audit (build health, certificates, crash reports, architecture and test coverage) and reproduce faults before fixing them. Happier Meditation’s apps moved to Diffco during a major team transition.
Usually the current major version and one or two before it, decided from your analytics rather than habit. Supporting older versions costs testing time, so we show you the trade-off in users and effort before you choose.
Yes. Internal apps go through the right Apple channel: unlisted App Store distribution, custom apps through Apple Business Manager, or in-house distribution where you qualify. We choose it before the build, so review doesn’t send you back to the start.
Yes. Apple’s Foundation Models framework runs a language model on the device, on supported hardware: fast, private, with no per-call cost. Where it isn’t enough, we call cloud models through your back end, with evals and limits on every call.
Each September Apple ships a new iOS, and by the following spring App Store uploads must be built with its SDK. We test on the betas from June and fix what breaks before your users see it.
Yes. We build native Android in Kotlin, cross-platform apps in React Native and Flutter, and the back ends behind them: one team, one plan, no hand-offs between vendors.
Focused apps can reach the App Store in about three months: WYA’s MVP did. Larger products ship in releases, with a clickable prototype in the first weeks and TestFlight builds soon after.
Engagements start with a fixed-price audit or discovery, agreed up front. Builds run on a monthly team allocation or a fixed scope after discovery, with the estimate given as a range and the open questions that make it wide.
You do. The Apple developer account, certificates and App Store listing are in your name from day one, and the code, plan, rules and decision log are kept in your repo.
Need other services?
React DevelopmentSenior React engineers build fast, accessible front ends: new products, takeovers and React 19 upgrades.
Node.js DevelopmentSenior engineers build Node.js APIs and real-time services in TypeScript, and take over the ones that have grown hard to change.
Vibe Code RescueYour Lovable, Bolt, Replit or Cursor prototype worked. Our senior engineers stabilize, harden or rebuild it for production.
Mobile DevelopmentNative iOS and Android apps, with AI features built in, designed for real users from the first release.
AI & ML DevelopmentML, RAG, computer vision, and copilots, engineered to production standards with Production-Ready AI Engineering.
Custom Software DevelopmentWeb apps, platforms, and internal tools, built in weeks instead of months, from PoC to production.
