glueglue™ | Migrating an existing app to Flutter: when it makes sense and how to do it

Two separate apps for iOS and Android, two teams, two backlogs, features landing on one platform weeks after the other and double the maintenance costs. It's a common situation for companies that built their apps natively years ago. Migrating to Flutter unifies everything into a single codebase, but it isn't a decision to take lightly.

Let's look at when migration really pays off, which strategies are available and how to reduce the risks for users and for the business.

Why companies migrate to Flutter

A single codebase: iOS and Android share logic and UI, and every feature is built once.
Lower maintenance costs: updates, bug fixes and OS adaptations happen in one project.
A consistent experience: identical design and behaviour on every platform, with near-native performance.
Beyond mobile: the same codebase can also power web and desktop versions.

The same Flutter app on Android: one codebase for multiple platforms

When to migrate (and when not to)

Migration makes sense when the app is a strategic product that will keep evolving, when the two native versions have drifted apart, or when the existing code has built up so much technical debt that every release slows down. It's also the right moment if a redesign is already planned.

It's better to wait if the app is stable, rarely updated and works well, or if it relies heavily on very specific hardware features that would require a lot of native code anyway.

Flutter, Google's cross-platform framework

Three migration strategies

1. Full rewrite

A new Flutter app is built from scratch to replace the native versions. It's the cleanest route and often the fastest for medium-sized apps, especially if you use the opportunity to rethink UX and architecture.

2. Incremental migration with add-to-app

Flutter can be embedded inside an existing native app, screen by screen. You start with new or critical sections and proceed gradually, reducing risk. It's the ideal approach for large apps with many active users.

3. Hybrid, module-based approach

Modules with heavy native dependencies stay native and talk to Flutter through platform channels, while the rest of the UI and logic is unified.

Gluto, an app built by GlueGlue with Flutter

How to run a migration project

Technical and functional audit: map screens, integrations, native dependencies and data to preserve.
Choose the strategy and release plan, with priorities based on business value.
Design: align the interface and create a design system shared across platforms.
Development and automated testing, with particular care for login, payments and local data migration.
Gradual release through staged rollouts on the stores, monitoring crashes and metrics.

Risks to manage

The sensitive points are always the same: not losing user data and sessions, keeping the same bundle ID so the app is updated rather than reinstalled, preserving reviews and store rankings, and not breaking integrations with company systems. A dedicated test plan and a progressive rollout keep these risks to a minimum.

Migrating to Flutter: frequently asked questions

How long does it take to migrate an app to Flutter?

For an app of medium complexity, roughly 3-6 months. With an incremental approach the work is spread over several releases, but users see improvements sooner.

Will users lose their data?

No, if the migration is planned properly. The app is published as an update to the same app, and local data and sessions are migrated transparently.

Is Flutter suitable for enterprise apps?

Yes. It's used by large companies in sectors such as banking, retail and automotive, and it's backed by Google with a mature ecosystem of libraries and tools.

Conclusion

Migrating to Flutter is an investment that pays back in development speed, a consistent experience and lower maintenance costs, provided you choose the right strategy and manage the transition carefully. GlueGlue is a Google Flutter partner in Italy and supports companies from the initial assessment to the release of the new app.

Let's talk about your project: get in touch with the GlueGlue team

Our replies
to your questions

Why choose glueglue?

We are a digital product agency with over 10 years of experience and advanced expertise in design and development. We have refined an agile and effective method, suitable for both startups and large enterprises, ensuring execution speed and consistent quality. We position ourselves in the upper‑mid range of the market, offering excellent value for money. Every project is overseen directly by the founding partners to ensure outstanding results. We are among the top User Experience and digital product agencies on Clutch, the leading global database for digital consulting.

How does glueglue work and what are your areas of expertise?

We start with an in‑depth needs analysis, considering product and business objectives in the medium to long term. We often begin with visual identity: we assess positioning, analyze competitors, and identify opportunities to improve brand and image. We then move to UX/UI: we conduct a professional UX Review to identify areas for intervention and improve the usability of the site or app. We design the User Journey Map, mapping all touchpoints to understand real use cases and where to create tangible value. We create wireframes and share an interactive prototype that defines the functionality, structure, and interactions of each page. Once the wireframes are consolidated, we refine the interface design in detail to ensure a pleasant and consistent experience. Finally, our developers implement the product with modern technologies such as React, Flutter, Symfony, Svelte, Node.js, and more, ensuring quality, stability, and pixel‑perfect results.

Do you use artificial intelligence?

Yes, on two fronts. Inside our own method, where it helps designers explore and compare several directions in hours instead of days, and helps engineers accelerate repetitive phases and raise quality with broader review and testing.
And inside the products we build for our clients: document and file analysis, predictive models, understanding of unstructured text, semantic search, assistants and automations.
For us it is a multiplier, not a shortcut: people stay in the loop and every AI feature has a success metric defined before it is written. Read how we use AI.

What sets glueglue apart from other top design or product agencies?

We work on a limited number of projects to maintain constant focus and achieve excellent results. We manage each project with clear deadlines and regular meetings, building tailor‑made, truly customized solutions. With over 10 years of experience in digital, we apply a proven method that maximizes results in strategy, design, and development.

Can you handle web design?

Yes. We work on iOS/Android apps, web apps, and complex platforms. A dedicated team also creates marketing websites, sites designed to effectively promote products or services.

Do you also do branding or should I look for another agency?

We are a full‑service agency and offer branding services such as naming and logo design. We produce complete brand guidelines and work both on existing guidelines and in collaboration with other branding agencies.

How much does it cost to entrust you with a digital project?

We believe in transparency: talking openly about budget helps create value for both sides. Every client has different needs, which is why we don’t use a fixed price list. Instead, we take the time to understand the context and propose a tailored approach with a fair, appropriate investment. Our UX/UI design projects start at €15,000, while branding engagements begin at €8,000. Mobile app development typically requires an investment starting from €40,000, web apps from €30,000, and websites from €15,000. Our average hourly rate for consulting is €70/hour.

Do you also work with early‑stage startups, therefore with limited resources?

Absolutely yes: we love startups and often collaborate with talented entrepreneurs. We have invested in multiple ventures, favoring work for equity, contributing to funding rounds totaling over €30 million.

Migrating an existing app to Flutter: when it makes sense and how to do it

Why companies migrate to Flutter

When to migrate (and when not to)