What is Flutter? Guide to Flutter for 2024

What is Flutter?

Developed by Google in 2017, Flutter is a free and open-source cross-platform mobile UI framework and is based on a programming language called Dart. It allows mobile app development for both iOS and Android apps from the same codebase. Since its release, Flutter has gained an incredible amount of support from the development community, drawing direct comparisons to the more established cross-platform app-development competitor, React Native. Flutter not only supports iOS and Android mobile development, but also web, macOS, Windows, Linux, and embedded systems (such as those in infotainment systems for vehicles). Flutter 4 will be focusing on increasing functionality for desktop systems.

There are two key components to Flutter:

Software Development Kit

The Flutter software development kit offers tools to help with the development of applications, including:

UI Framework

In addition to the tools for building and coding your application, Flutter also strongly supports UI design by delivering:

What is Dart?

Dart programming language is the foundation of the Flutter app development framework. Not only does it provide the language and runtimes powering Flutter applications, but it also supports core developer tasks like formatting, analyzing, and testing code. It is designed to be optimized for UI development, providing the same experience across all platforms. And by all platforms, we don’t mean just Android and iOS devices. Dart supports development for iOS, Android, Linux, Windows, and web development projects.

Dart is designed to build apps quickly and to help developers avoid mistakes during development, saving rework and testing time. For example, it is type-safe, meaning that it leverages static type checking to make sure that a variable’s value always matches the variable’s static type. It also offers sound null safety, meaning that values cannot be null unless the coder says explicitly that they can be. This prevents null value exceptions at runtime through static code analysis. These are just some of the features designed to prevent mistakes and make this programming language easier to learn and use.

Dart is a very well-supported language, offering a rich set of core libraries, a comprehensive set of APIs delivered via packages (many packages developed by the Dart team themselves), not to mention rich community support including a large number of third-party publishers providing thousands of additional packages.

How does the Flutter UI Work?

Flutter as a cross-platform app development framework is known for creating fast, responsive, and slick UIs across both iOS and Android apps. But how does it work? What makes it different from its key cross-platform competitor, React Native? One key difference between these frameworks is Flutter’s use of widgets. These widgets, drawn on the Skia canvas, are the foundation of the Flutter UI, allowing for a very consistent and unified object model, as well as allowing for very rapid UI design development.

Objects in Flutter are all widgets, whether a button, padding, or a font, and can be combined in any manner to create custom layouts. You can leverage already-developed widgets to save considerable time or create custom Flutter widgets using the same toolsets as the Flutter team. Flutter renders widgets from an organized tree structure, which is good for rendering, but can be complicated. A large application might require up to ten layers of code to render simple objects, making careful planning a priority.

Another key difference is that the Flutter UI does not rely on native components. By leveraging the same widgets across both iOS and Android apps, Flutter can deliver the exact same experience across both platforms and arguably deliver better performance as there is no need to bridge the native components. However, sometimes a unified experience is not desirable. Because of the competition between platforms, and because both Android users and iOS users have a stated preference for native apps on their platform of choice, it is sometimes desirable to fool native users into thinking that the application is built with native code, using native UI elements. This can be done with Flutter cross-platform app development, but unfortunately requires divergent builds, with stateful and stateless widgets designed to mimic Android UI components (Material Components) or iOS UI components (Cupertino).

Is Flutter Native?

As you might have surmised from the above Flutter UI description, Flutter app development is not native app development. It delivers native performance and can deliver a native user experience, but it leverages a separate codebase and framework from both iOS and Android while remaining compatible with both. With one programming language and one code base, it allows you to deliver apps for multiple different platforms, including but not limited to iOS and Android devices.

Is Flutter Performant?

Flutter performance often draws strong comparisons to native app performance. Because it bypasses system UI libraries, and uses its own widget set, also embedding its own copy of Skia Canvas, the Flutter engine provides top-tier performance metrics comparable to native code.

In general, Flutter provides (or aims to provide) 60 frames per second (fps) performance, or 120 fps performance on devices capable of 120Hz updates.

Advantages of Flutter

Flutter has many advantages. These advantages go beyond the benefits of cross-platform development, and the resultant time saved when compared to native app development for both mobile platforms. Notable advantages include:

Drawbacks of Flutter

While Flutter has distinct advantages, no product is right for every project. The cross-platform mobile app development market is pretty much dominated by two players, React Native and Flutter. Any time there is such strong competition, it is clear that both have selling points. Disadvantages are relative, and usually in comparison to another product or service. Let’s look at some general drawbacks, and then compare them to other solutions:

Dart/Flutter reliance – Dart programming language is pretty much only used for Flutter projects, and Flutter relies on Dart. If Flutter lost popularity, Dart programming language would likely all but disappear. If Dart lost popularity, Flutter would be hard-pressed to gain further traction. This is not the case with React Native, as it is based on JavaScript, which is used worldwide for web, mobile, and PC apps. Likewise, native development is not at risk in the same manner, because native machine code is often leveraged within cross-platform development for complex features, and will always hold advantages for specific platform development.

Google/Android Focus – While Flutter works very well on iOS, Flutter is still developed by Google, which means that problems for iOS or other platforms will likely always receive less priority than issues for Android applications.

Flutter vs. React Native

Both Flutter and React Native are excellent choices for high-quality apps on both iOS and Android. However, each has its strengths and weaknesses, particularly in comparison with the other. In fact, we’ve covered this topic in depth. But for the purposes of this article, let’s take a look at some of the key points. 

Dart/Flutter Expertise – While Flutter and Dart draw praise for being easy to learn, whether for beginners or if coming from native app development, it is still a bit more difficult to find top-tier resources for Flutter/Dart than it is to find React Native specialists. It is gaining popularity and has a strong community, and because it is easier to learn, there are many beginning developers and journeymen out there, but Flutter has a way to go to catch up to React Native in terms of pervasiveness in the development community.

MVP Development/Time to market – Flutter was already a strong choice for MVP development, due to faster UI development with widgets, and hot reload to test small changes, but now also offers Flutterflow, a tool for MVP development that offers widgets with functionality pre-configured for elements such as chats, push notifications, etc. If you want to stand up a basic version of a cross-platform app quickly with several commonly used features, building apps with Flutter may be the right choice.

Programming Language – As mentioned earlier, JavaScript is never going away. It is far too pervasive, with multiple frameworks based upon it, and use in nearly every part of the web. Dart, on the other hand, is really only used in Flutter, and its success is currently tied to the success of this cross-platform framework.

Native appearance – When your goal is to make an application appear native on each platform (and there is a bias on each platform for native apps, especially on iOS) this is accomplished far more dynamically and with less maintenance via React Native. React Native leverages native platform components, and auto-updates with the native platform updates to use the latest platform components. Flutter can mimic the appearance of native apps as well but leverages particular widgets for each, Cupertino for iOS and Material Component for Android, but these must be updated manually on each platform, and also can be considered code differentiation between platforms that can add minor overhead to the project.

Size of applications – Because Flutter must include its own SKIA canvas and UI framework (widgets) in any application it creates along with the standard framework requirements and application code, Flutter apps tend to be larger than React Native or native apps. However, even if bulkier, including its own set of assets, is a reason Flutter performance can be higher, as it doesn’t need to ‘bridge’ to native components.

Ecosystem – React Native’s ecosystem is huge in comparison to Flutter, due primarily to the NPM library. There are over 1.8 million packages hosted on NPM, and numerous third-party libraries available to boot. Flutter has not had enough time to develop an eco-system to match, but still offers a robust enough eco-system to compete for most use cases.

Flutter vs. Native Development

The most obvious benefit of Flutter is of course the ability to deliver an application across numerous platforms (not just iOS and Android) with a single codebase. But are there still reasons to use native code?

Performance – It is far simpler to build performance into high-quality native apps than into cross-platform, and it is likely that native apps will always maintain a lead in the performance category. However, Flutter’s performance is nearly on par because it bypasses native components in favor of its own canvas. Both React Native and Flutter apps can deliver performance for your next app that is almost indistinguishable from the user’s perspective. Native apps do tend to use less memory and CPU than cross-platform frameworks.

Code maintenance – As you might guess, the same benefits exist for maintaining a cross-platform app as for developing one. It is far easier to maintain a cross-platform app using a single codebase across multiple platforms than to maintain separate codebases.

Native feature benefits – Native app development can leverage sophisticated platform features such as GPS, high-end camera functionality, accelerometer, and others better or more simply than cross-platform frameworks like Flutter and React Native. For particularly intensive use cases of these features, there may be an argument for leveraging native code. However, these use cases are not particularly common.

When to Avoid Flutter

There are several situations in which Flutter development may not be the best choice for your organization, despite its numerous advantages.

Existing expertise – If you have an existing team of JavaScript and React/React Native experienced developers for existing web apps or desktop apps, and can reuse components or code, then React Native will likely be easier to implement.

Human Resources/Timeline constraints – If you do not already have a Flutter-capable team, it can be much faster to source JavaScript/React Native resources to create a new team or fill gaps than to find Flutter resources.

Specific Feature performance – If the performance of particular native features (such as advanced GPS, camera, or accelerometer) there may be a reason to leverage native mobile development.

OS-tied Updates – If your app updates regularly based on OS-tied updates, native mobile applications may be the way to go – or if the primary concern is simply the UI components, React Native.

Summary

Flutter is now a well-established player in the cross-platform mobile development market, in direct competition with the arguable ‘king of the hill’, React Native. While it has a way to go in terms of building a competing community and a large repository of third-party libraries, by some metrics it has matched or even surpassed its predecessor. It offers everything you need as a solid foundation for your cross-platform applications, including support for automated testing, fast and easy delivery of custom user interfaces, and tools to help speed up the development process. Flutter is not just for Android and iOS devices but also supports web applications and desktop app development (Linux, MacOS, and Windows), all with a single codebase.

While it can be more difficult to build a team of Flutter developers, don’t let it dissuade you from a solid option for your software development and custom mobile app development projects; with the right staff augmentation partner, such as Flatirons, a team can be built for you, or the gaps in your existing team can be filled quickly. While Flutter may not be right for every organization or every project, it certainly offers enough benefits and advantages to be considered for any cross-platform development project.

Frequently Asked Questions

Is Flutter a Programming Language?

Flutter is a cross-platform development framework, not a programming language.

What Language is Flutter?

Flutter is based upon Dart programming language, an open-sourced, object-oriented programming language with support for multiple different platforms, allowing you to create mobile applications, web applications, and desktop applications from a single codebase.

What are some well-known apps built using Flutter?

Many well-known applications were built with Flutter, including: