Four Major Integration Methods for Mobile Applications

1. API/SDK Integration
This approach involves one application integrating directly with another through APIs or by incorporating the other's SDK.

Advantages:

Deep functional integration enables seamless user experiences
Full access to native device capabilities
High performance with direct communication
Consistent branding and user experience
Precise control over data exchange and workflow

Disadvantages:

Highest development complexity and maintenance burden
Requires ongoing version management as either app updates
Security vulnerabilities if implementation is flawed
Significant testing required across multiple platforms and versions

Real-world example: A food delivery app integrating a payment processor's SDK. Users complete their entire transaction without leaving the delivery app, with the payment process appearing as a native part of the checkout flow.

How it looks to users:

Users stay entirely within the food delivery app

Payment screens match the app's design language

Transaction processing appears seamless

Receipt and confirmation occur in the original app

2. Deep Linking / SSO Integration
This method allows users to jump from one application to another through specialized links, often utilizing single sign-on for authentication.
Advantages:

Moderate development effort compared to API/SDK integration
Clear separation of responsibilities between applications
Each application maintains control over its core functions
Reduced dependency issues between applications
Simpler maintenance as apps can evolve independently

Disadvantages:

Disrupts user flow by switching between applications
Potential for broken experiences if the target app isn't installed
Navigation complexity increases with frequent app switching
Authentication state management challenges

Real-world example: A social media app allowing users to share content to WhatsApp. When the user taps "Share via WhatsApp," the device transitions to the WhatsApp app with pre-populated content.
How it looks to users:

Visible app transition with animation

Content from the original app appears in the target app

After completing the action, users must manually navigate back

Authentication state may persist across apps via SSO

3. Web Redirection with Token Exchange
In this approach, the application redirects to a web-based interface, often with secure token exchange for maintaining context and authentication.
Advantages:

Lower development complexity than native integration methods
Consistent experience across platforms without multiple implementations
Easier to update without requiring app store approval
Reduced version compatibility concerns
Better fallback options when applications aren't installed

Disadvantages:

Limited access to device capabilities
Network dependency creates potential points of failure
Performance limitations compared to native implementations
Less polished user experience with visible redirections
Requires careful security implementation for token exchange

Real-world example: A banking app letting users connect their accounts to a budgeting service. The app opens a secure browser that navigates to the budgeting site's authorization page, passing secure tokens.
How it looks to users:

App transitions to a browser interface

URL bar and browser controls become visible

Authentication typically doesn't require re-login (token-based)

Users complete the flow within the browser before returning

Often includes a "Return to App" button after completion

4. WebView / Embedded Web Integration
This involves embedding web content directly within the native application through WebViews or similar technologies.
Advantages:

Unified user experience without visible application switching
Rapid deployment of updates without app store approval cycles
Single codebase for the embedded functionality across platforms
Reduced development cost for cross-platform features
Ability to leverage existing web-based systems

Disadvantages:

Performance limitations compared to fully native implementations
Restricted access to device capabilities
Memory usage concerns with heavy web content
Debugging complexity when issues occur
Security considerations with JavaScript bridges

Real-world example: An airline app embedding its web-based seat selection tool. Users see the seating chart and make selections without leaving the app, though the content is actually rendered web content.
How it looks to users:

Appears to be in the native app without transition

May show subtle visual differences in design and behavior

Custom headers/footers often frame the web content

Network loading indicators may appear

Scrolling and interaction might feel slightly different from native elements