What is a mobile app?

A mobile app is a software program designed to run on a smartphone or tablet. Unlike a web app, it is downloaded from a distribution platform such as the Google Play Store or Apple App Store and installed directly on the device, giving it access to hardware features a browser cannot reach.

How mobile apps differ from web apps

Because a mobile app runs natively on the device rather than inside a browser, it can use the camera, GPS, biometric sensors, accelerometers, and on-device storage. It can also function offline, queuing actions until connectivity returns. These capabilities make mobile the preferred surface for services where location, identity, or real-time sensor data matter.

The trade-off is distribution. Every release must pass platform review, revenue is shared with the platform holder, and visibility depends on app store ranking and ratings.

Development approaches

Mobile app development follows one of three main patterns:

Native development targets a single platform using its primary language, Swift or Objective-C for iOS, Kotlin or Java for Android. Native apps have the closest access to platform APIs and typically deliver the best performance and platform consistency.

Cross-platform frameworks such as React Native and Flutter let teams share most of their codebase across iOS and Android. This reduces cost and keeps feature parity easier to maintain, though some platform-specific behaviours still require native code. See also the pros and cons of React Native for mobile development.

Progressive web apps (PWAs) use web technologies but can be installed from a browser, work offline, and send push notifications. They do not require app store submission but cannot access the full range of device APIs that native or cross-platform apps can.

For teams evaluating the broader front-end picture, the difference between React and Next.js is relevant context for choosing a web companion to a mobile product.

Categories of mobile applications

Mobile apps span almost every domain, but most fall into recognisable categories:

• Productivity and business: email, document editing, project management, internal tooling
• Entertainment and media: video streaming, mobile gaming, audio
• Social and communication: messaging, social networks, community platforms
• Utility and lifestyle: navigation, weather, fitness, food delivery
• Commerce and finance: shopping, banking, payments, investment

Each category places different demands on the underlying architecture. A real-time multiplayer game has different backend requirements from a banking app, though both must handle authentication, data integrity, and offline states carefully.

Backend considerations

Most mobile apps depend on a backend for data persistence, authentication, and business logic. Teams with limited backend resource often reach for a backend-as-a-service platform. Firebase and Supabase are the most common choices; the difference between Firebase and Supabase is worth understanding before committing to either.

Security and privacy

Mobile apps handle sensitive data ranging from personal messages to financial transactions. Key requirements include encryption of data at rest and in transit, secure authentication, and compliance with regulations such as GDPR and CCPA. Both platform stores apply security screening, but responsibility for secure coding, dependency management, and timely patching remains with the development team. Apps incorporating AI features should also account for prompt injection risks if they expose model interactions to user input.

Distribution and discoverability

The App Store and Google Play each have their own review guidelines, revenue-share structures, and ranking algorithms. App store optimisation, ratings management, and staged rollouts are operational disciplines in their own right. Platform holders can reject or remove apps for policy violations, making compliance a continuous concern rather than a one-time check.

Emerging capabilities

Several developments are extending what mobile apps can do:

• AI integration: on-device models and cloud-backed inference now power features such as image recognition, personalised recommendations, and voice interaction. Retrieval-augmented generation is increasingly used to ground responses in product-specific data.
• IoT control: mobile apps serve as the primary interface for connected hardware, from consumer smart-home devices to industrial equipment.
• AR and VR: growing device capability makes augmented-reality features practical for retail, navigation, and training applications.
• 5G: lower latency and higher bandwidth open categories that were impractical on 4G, including real-time collaborative experiences and cloud-rendered graphics.

In an AI-native team

Coding agents can scaffold a new screen, generate boilerplate platform code, and draft test cases faster than any individual developer working alone. In practice this shifts effort towards reviewing AI-generated code for platform-specific correctness, verifying that generated networking or storage code handles edge cases, and maintaining context engineering so agents produce output that fits the existing architecture rather than generic examples. Engineers who understand native platform constraints are better placed to catch the subtle errors agents introduce in areas like lifecycle management or background processing.

What we test for

When assessing mobile engineers we follow how we vet: a fundamentals assessment without AI tools checks platform knowledge, architecture reasoning, and the ability to read and reason about code the candidate did not write, which matters when inheriting a codebase. An AI-native session then evaluates how well the candidate steers agents, verifies generated output, and catches plausible-looking errors, the skills described in how to assess an engineer's AI ability.

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