Rebuild without starting over. Migrate without losing users.
Legacy mobile apps accumulate technical debt in ways that eventually make them unmaintainable: Objective-C codebases nobody on the current team can read, Xamarin apps on a framework Microsoft is sunsetting, React Native apps on the old bridge architecture with dozens of incompatible dependencies, or Flutter apps stuck on null-safety migrations. The instinct is a full rewrite — but a full rewrite is a high-risk gamble on rebuilding everything correctly the second time. We use a proven incremental approach: identify the parts of the existing app that are worth keeping, migrate them to the new platform or framework, and replace the rest module by module while the existing app stays in production.
Legacy mobile apps accumulate technical debt until they become unmaintainable. The instinct is a full rewrite, but rewrites are high-risk. Origin Softwares uses an incremental approach: characterisation tests document existing behaviour, migration happens module by module, and the production app keeps shipping updates throughout the process.
When should you modernize or migrate a mobile app?
Modernize when the framework is deprecated (Xamarin, Ionic, old React Native), when the codebase has accumulated so much technical debt that changes are expensive and risky, when minimum OS version requirements lock out modern APIs, or when the original developers are gone and nobody can maintain the code safely. A practical signal: if a feature that should take one sprint now takes three because of fear of breaking unrelated things, migration is overdue. Origin Softwares runs a legacy audit first — assessing whether incremental migration or a full rewrite is more cost-effective. Most apps can be migrated incrementally, which is lower risk than a rewrite because the existing app stays in production throughout.
The problems this solves
- App built on a deprecated framework (Xamarin, Ionic, old React Native bridge architecture)
- Original developers are gone and current team cannot safely modify the codebase
- Technical debt making every change expensive and risky
- Cannot upgrade minimum OS version without breaking features
- Third-party SDK dependencies are outdated and unsupported
- Full rewrite risk is too high — cannot afford to rebuild incorrectly
Business outcomes
- Zero user-facing regressions in migrations (characterisation tests guarantee it)
- App Store rating maintained through migration (4.5+ average maintained)
- Migrated codebase on a supported, modern framework reducing ongoing maintenance cost
- Production app keeps shipping updates during migration (no feature freeze)
- Modern architecture enabling feature development at lower cost going forward
- Reduced crash rate and improved performance on modern framework
Who is this for?
Xamarin apps needing migration
Xamarin.Forms was deprecated — migration to Flutter is the most common path, deliverable in 3–5 months.
React Native apps on old architecture
The old bridge architecture has performance limitations — migration to New Architecture can happen incrementally.
Apps with unmaintainable codebases
Original developers gone, no tests, no documentation — we audit and establish a safe migration path.
Apps needing OS version upgrades
Dropping support for old OS versions unlocks modern APIs but requires careful testing and communication.
Apps with outdated dependencies
Third-party SDKs that are no longer maintained create security risks and compatibility issues.
When Mobile App Modernization & Migration may not be the right fit
We'd rather tell you upfront than waste your time and budget.
- If the app is small enough that a clean rewrite is faster and cheaper than incremental migration
- If the feature set has changed so much that the existing app's behaviour is irrelevant to the new requirements
- If the codebase has no users — there is nothing to preserve through careful migration
- If the budget supports a full rewrite and the risk is acceptable given thorough specification
What's included
- Legacy codebase audit & risk assessment
- Framework migration (Xamarin → Flutter, RN old arch → new arch)
- iOS/Android version compatibility upgrades
- Third-party SDK & dependency modernisation
- Incremental feature migration strategy
- Zero-regression testing during migration
How we deliver
Legacy Audit
Assess the existing app and recommend whether to migrate or rewrite.
- Codebase quality assessment
- Dependency and SDK inventory
- Test coverage evaluation
- Architecture analysis
- Migration vs rewrite recommendation with rationale
Safety Net
Write characterisation tests before changing anything.
- Characterisation test suite for existing behaviour
- Edge case and quirk documentation
- Performance baseline measurement
- Device compatibility baseline
- Parallel testing infrastructure setup
Module Migration
Migrate module by module with parallel testing after each.
- Module prioritisation (highest value or highest risk first)
- Migration implementation per module
- Parallel testing (old vs new comparison)
- Regression verification against characterisation tests
- Production app continues shipping updates
Cutover
Switch users to the migrated app via a single store update.
- Full parallel test suite passing
- Store listing update preparation
- Single store update to migrated version
- Crash rate and rating monitoring
- Post-cutover stabilisation support
How do you migrate a mobile app without breaking it?
Origin Softwares writes characterisation tests before touching any code — tests that document what the existing app currently does, including edge cases and quirks that users depend on. The migration happens module by module with parallel testing: old and new versions run simultaneously, comparing outputs. Only when both agree on every tested scenario do we retire the old code. The production app keeps receiving bug fixes and minor updates throughout the migration, so there is no feature freeze imposed on the business during a typically 3–5 month process. Users experience a single store update to the migrated version — they never see two parallel apps.
Technologies we use
- Flutter
- Kotlin
- Swift
- React Native (New Arch)
- Firebase Test Lab
- Detox
- XCTest
- Espresso
- Fastlane
- GitHub Actions
Architecture & scalability
- Target framework chosen based on existing team skills and future requirements
- Characterisation tests as the primary safety mechanism throughout migration
- Module boundaries defined to enable independent migration of each module
- Data layer migration planned separately from UI migration
- Backward-compatible API contracts maintained during gradual migration
- CI/CD pipeline supporting both old and new codebases during transition
Migration vs Rewrite
| Criterion | Incremental Migration (Our Default) | Full Rewrite | Optimise in Place |
|---|---|---|---|
| Risk level | Lower — characterisation tests provide safety net | Higher — rebuilding from specification risks missing behaviour | Lowest |
| Production continuity | Production app keeps shipping updates | Feature freeze during rewrite period | Continuous |
| Timeline | 3–6 months typical | 4–8 months typical | Weeks |
| Cost predictability | High — phased scope with known boundaries | Less predictable — scope discovery during build | High |
| Feature preservation | All tested behaviour preserved by construction | Depends on specification completeness | Full preservation |
| Best for | Apps with active users and complex feature sets | Small apps or apps where requirements have changed fundamentally | Apps that just need dependency updates and performance work |
Why choose Origin Softwares
Our approach
- Characterisation tests written before a single line of code changes — the safety net exists before work begins
- Parallel testing (old vs new) until parity is proven on every scenario
- Production app keeps shipping during migration — no feature freeze required
- Zero user-facing regressions across all migrations we have delivered
Delivery standards
- Legacy audit report before any migration commitment
- Characterisation test suite covering existing behaviour
- Module-by-module migration with parallel testing
- Production app continues receiving updates throughout
- Store rating monitored through migration
Quality assurance
- Characterisation tests documenting current behaviour before migration
- Parallel testing — old and new versions compared systematically
- Regression testing after each module migration
- Device testing across the same matrix as the existing app
- Store rating and crash rate monitoring throughout
Security practices
- Dependency vulnerability assessment as part of audit
- Outdated SDK replacement with current, maintained alternatives
- Security posture improvement as a migration benefit
- No legacy security patterns carried forward (obsolete encryption, insecure storage)
- Modern authentication patterns applied during migration
Performance
- Performance baseline established before migration begins
- Performance regression testing after each module migration
- Modern framework performance benefits captured (faster startup, smoother UI)
- Bundle size reduction through modern build tooling
- Memory and CPU profiling on target devices
What you receive
- Legacy audit report with migration recommendation
- Characterisation test suite (reusable for ongoing regression testing)
- Migrated app submitted to both stores
- Migration documentation for future maintenance
- Performance comparison report (before vs after)
Support tiers
- Migration support — the migration project itself with defined phases and milestones
- Post-migration stabilisation — 30 days of monitoring and bug fixes after cutover
- Ongoing maintenance — continued development on the modernised codebase
Why Origin for Mobile App Modernization & Migration
Characterisation tests before a single line changes
We document current app behaviour — including the bugs users have come to depend on — before making any changes. The regression safety net exists before demolition begins.
Parallel testing: old vs new until parity is proven
We run both versions simultaneously during testing, comparing outputs systematically. We don't retire the old code until the new code matches it on every tested scenario.
Production keeps shipping during the migration
An incremental migration doesn't require a feature freeze on the existing app. We plan phases that absorb production releases so your users get bug fixes while the migration runs.
Industries we serve
Typical delivery timeline
| Phase | Duration | What happens |
|---|---|---|
| Audit | 1–2 weeks | Codebase assessment, recommendation |
| Safety Net | 1–2 weeks | Characterisation tests, baselines |
| Migration | 8–16 weeks | Module-by-module migration with testing |
| Cutover | 1 week | Store update, monitoring, stabilisation |
Before you start — a checklist
Use this to prepare for your first conversation with us.
- Assess whether the existing codebase has any test coverage (this affects audit complexity)
- Identify whether the original developers are available for knowledge transfer
- Determine the target framework (Flutter is most common for Xamarin migrations)
- List all features and prioritise which must work identically after migration
- Decide whether a feature freeze during migration is acceptable or production must keep shipping
- Confirm the minimum OS version target for the migrated app
Maintenance & support
- 30-day post-cutover stabilisation and monitoring
- Crash rate and store rating monitoring during transition
- Ongoing maintenance on modernised codebase
- OS compatibility updates on modern framework
- Feature development on clean architecture
- Characterisation test suite maintained for ongoing regression protection
“Our Xamarin app had 40,000 active users and six years of accumulated features. Origin migrated it to Flutter in four months without a single regression complaint from users. The new app loads in half the time.”
Frequently asked questions
Planning & scope
- Our app is on Xamarin — what are our options?
- Xamarin.Forms was deprecated in May 2024. .NET MAUI is the Microsoft successor but carries its own ecosystem immaturity. For most Xamarin apps, we recommend migrating to Flutter — same cross-platform use case, larger ecosystem, better tooling, longer-term future. Migration scope depends on app size — most Xamarin apps migrate in 3–5 months without users noticing the transition.
- When should we rewrite instead of migrate?
- Rewrite when the existing codebase has no tests and the original developers are gone (impossible to know what behaviour is intentional vs accidental), when the architecture is fundamentally incompatible with the target, or when the feature set has changed enough that migration and rewrite have similar scope. In most cases, even a codebase in poor condition can be migrated incrementally — we assess honestly after the audit.
Technical
- How do you prevent regressions during migration?
- Characterisation tests written before touching anything — tests that document what the existing app currently does. Migrated modules are tested against the same cases. We run old and new versions in parallel, comparing outputs. Only when both agree on every tested scenario do we retire the old code. The safety net exists before any migration work begins.
- Can you migrate while we keep releasing updates?
- Yes — this is our standard approach. The migration runs in a separate branch while the production app continues receiving bug fixes and minor updates. We plan migration phases to absorb production changes. Users are migrated in a single store update — they do not experience two parallel apps or a feature freeze.
Engagement & process
- How long does a typical migration take?
- Xamarin to Flutter: 3–5 months. React Native old architecture to new: 4–8 weeks. General modernisation (dependency updates, OS compatibility): 2–6 weeks. The audit determines scope — we provide a timeline after understanding the codebase, not before. A migration estimate without an audit is a guess.
- What if the audit says rewrite is better?
- We tell you honestly. If the codebase is so degraded that characterisation testing is impractical, or the feature set has changed enough that migration saves no effort over a rewrite, we recommend the rewrite with a clear scope document. The audit fee is not wasted — it prevents committing to a migration that would have been more expensive than a rewrite.
Related services
Mobile App Development
After migration, the modernised app continues development within our mobile practice.
Custom Software
Backend modernisation often accompanies mobile migration — outdated APIs may need updating alongside the app.
IT Staffing
Augment your team with engineers experienced in the target framework for the migration build phase.
Not sure where to start?
Tell us what framework your app is built on, how many active users it has, and what is making it unmaintainable — we will assess whether migration or rewrite is the right path and give you an honest scope estimate.
Get a free consultation