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FirebaseSigns your mobile app needs modernization
Many companies built their first app years ago, and it shows: old frameworks, hard-to-change code, crashes on new devices and a design that feels dated next to competitors. Small changes take weeks because the codebase is fragile, and hiring developers for outdated technology is difficult.
Modernization brings the app back to a healthy state. Depending on its condition, that may mean upgrading dependencies, rewriting the UI in modern frameworks, moving to a cross-platform codebase or rebuilding the app around a new backend.
Problems we solve
- Built on Objective-C, Java, Cordova, Ionic v1, Xamarin or an outdated React Native version
- Separate iOS and Android codebases drifting apart
- Slow startup and poor ratings mentioning crashes
- A design that no longer matches your brand
- Every update takes far longer than it should
What’s included
App assessment
Code, architecture, dependencies, crash data and store reviews analysed.
Incremental upgrade
Dependencies, OS targets and frameworks brought up to date step by step.
UI modernization
Screens rebuilt in SwiftUI, Jetpack Compose, Flutter or modern React Native.
Cross-platform consolidation
Two native apps merged into one Flutter or React Native codebase.
Performance work
Startup time, memory, battery and network efficiency improved.
Backend & API updates
Modern APIs, authentication and push notifications.
Upgrade, refactor or rebuild?
| Option | When it fits |
|---|---|
| Upgrade in place | Code is reasonable; frameworks and dependencies are outdated |
| Incremental refactor | Valuable logic, but UI and architecture need rework |
| Rebuild | Obsolete technology (e.g. Cordova, Xamarin) or very poor code quality |
We recommend after the assessment, with costs for each option so you can weigh short-term spend against long-term maintenance.
Migrating from Xamarin and other retired frameworks
Microsoft ended support for Xamarin in 2024, and other older hybrid frameworks are no longer maintained. Apps built on them face growing security and compatibility risk. Typical migration paths are .NET MAUI for teams that want to stay in C#, or Flutter and React Native for broader ecosystems. We migrate in phases where possible, so users keep receiving updates during the transition.
Planning a modernization without disrupting users
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Audit1–2 weeks
Review code, dependencies, crash data, store reviews and the back-end APIs the app relies on.
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Define the target
Choose the framework, architecture and minimum OS versions, and decide what to keep, refactor or rebuild.
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Protect user data
Plan how login sessions, local data and settings migrate so users are not logged out or lose information.
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Rebuild in slices
Where possible, modernize screen by screen inside the existing app; otherwise build in parallel and switch over at a release.
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Release gradually
Use staged rollouts and feature flags, watching crash and review data at each step.
Choosing the target technology
| Situation | Typical recommendation |
|---|---|
| Two native apps with duplicated features and a small team | Consider consolidating on Flutter or React Native |
| Heavy use of device features, AR or demanding graphics | Modern native: Swift/SwiftUI and Kotlin/Jetpack Compose |
| Existing React web team and shared business logic | React Native |
| Ageing hybrid (Cordova, Ionic v1) app | Flutter, React Native or a PWA depending on device needs |
There is no universally right answer; the choice depends on your team, roadmap and device requirements. See cross-platform app development for how we weigh the options.
Modernizing the back end too
Many app problems blamed on the mobile code actually come from the APIs behind it: slow endpoints, chatty request patterns, missing pagination or outdated authentication. A modernization is a good moment to review these. Typical improvements include consolidating several calls into one purpose-built endpoint for each screen, adding caching, moving to token-based authentication with refresh rotation, and versioning the API so old app versions keep working while new ones adopt improved contracts. Supporting older app versions for a defined period avoids forcing every user to update on day one.
Auditing the app you have today
Every modernization starts with an honest audit, because the right plan depends on what is actually inside the current app rather than on how old it feels. We review the code, the build pipeline, the back end it talks to and the way it is released, then give you a written report with the risks ranked by impact.
| Area | What we check | Why it matters |
|---|---|---|
| Platform targets | Minimum iOS and Android versions, target SDK level | Stores reject updates that target outdated SDK levels |
| Dependencies | Outdated, abandoned or vulnerable libraries | Blocks OS upgrades and creates security exposure |
| Architecture | Separation of UI, business logic and data layers | Determines whether refactoring is practical |
| Test coverage | Unit, UI and end-to-end tests that exist and pass | Without tests, every change is risky |
| Build & release | Reproducible builds, signing keys, CI/CD | Lost keys or manual builds slow every release |
| Back-end contracts | API versions, authentication, error handling | Old app versions must keep working during rollout |
Rolling out a modernized app safely
A modernized app usually ships as an update to the existing store listing, so users keep their ratings, reviews and install base. To keep risk low we combine several release techniques:
- Phased store rollouts — release to a small percentage of users first and pause if crash rates or reviews move the wrong way.
- Feature flags — switch rebuilt screens on gradually, with the ability to fall back instantly.
- Forced and soft update prompts — encourage users onto supported versions without cutting anyone off abruptly.
- Backward-compatible APIs — older app versions keep working until usage drops to an agreed level.
- Data migration on first launch — local data, settings and logged-in sessions carried across so users do not have to start again.
Measuring whether modernization worked
Agree the success measures before work starts so the project can be judged on outcomes rather than effort. Useful measures include:
- Crash-free sessions and app-not-responding rates before and after
- Cold start time and screen load times on mid-range devices
- Store rating trend and the themes in new reviews
- Time taken to ship a typical feature or fix
- Number of releases blocked by build or dependency problems
- Percentage of users on the latest version within a few weeks of release
Common modernization mistakes
- Rewriting everything at once and freezing new features for months
- Changing the design, technology and back end in the same release
- Dropping support for older OS versions without checking how many users rely on them
- Forgetting accessibility, analytics or deep links that the old app supported
- Losing the original signing keys or store account access
- Treating modernization as finished instead of setting up ongoing maintenance
Once the app is current, a maintenance plan keeps it that way, so you never face another large catch-up project.
Budgeting for modernization
Modernization costs depend far more on the state of the existing code than on the size of the app. As a rule of thumb, a dependency and OS upgrade of a reasonably healthy app takes weeks, a screen-by-screen refactor takes a few months, and a full rebuild costs about the same as building a comparable new app. The audit gives you a range for each option, so you can compare them on cost, risk and time before deciding.
It also helps to separate the must-do work — store requirements, security fixes and OS compatibility — from the nice-to-have improvements, so the essential part can be funded and scheduled first.
Whichever option you choose, we keep the current app supported and releasable throughout the project, so urgent fixes never wait for the modernization to finish.
Related services
After modernization, keep the app healthy with mobile app maintenance. See also Flutter and React Native development.
This page is part of Mobile App Development Services — see the full overview for related services, approach and pricing.