Flutter is an

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

software development kit A software development kit (SDK) is a collection of software development tools in one installable package. They facilitate the creation of applications by having a compiler, debugger and sometimes a software framework. They are normally specific t ...

created by

Google Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

. It can be used to develop cross platform applications from a single

codebase In software development, a codebase (or code base) is a collection of source code used to build a particular software system, application, or software component. Typically, a codebase includes only human-written source code system files; thu ...

for the

web Web most often refers to: * Spider web, a silken structure created by the animal * World Wide Web or the Web, an Internet-based hypertext system Web, WEB, or the Web may also refer to: Computing * WEB, a literate programming system created by ...

Fuchsia ''Fuchsia'' ( ) is a genus of flowering plants that consists mostly of shrubs or small trees. Almost 110 species of ''Fuchsia'' are recognized; the vast majority are native to South America, but a few occur north through Central America to Mex ...

, Android,

iOS Ios, Io or Nio (, ; ; locally Nios, Νιός) is a Greek island in the Cyclades group in the Aegean Sea. Ios is a hilly island with cliffs down to the sea on most sides. It is situated halfway between Naxos and Santorini. It is about long an ...

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

macOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

, and

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

. First described in 2015, Flutter was released in May 2017. Flutter is used internally by Google in apps such as Google Pay and

Google Earth Google Earth is a web mapping, web and computer program created by Google that renders a 3D computer graphics, 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposition, superimposing satelli ...

as well as by other software developers including

ByteDance ByteDance Ltd. is a Chinese internet technology company headquartered in Haidian, Beijing, and incorporated in the Cayman Islands. Founded by Zhang Yiming, Liang Rubo, and a team of others in 2012, ByteDance developed the video-sharing ap ...

and Alibaba. Flutter ships applications with its own rendering engine which directly outputs pixel data to the screen. This is in contrast to many other UI frameworks that rely on the target platform to provide a rendering engine, such as native Android apps which rely on the device-level Android SDK or

IOS SDK The iOS SDK (iOS Software Development Kit), formerly the iPhone SDK, is a software development kit (SDK) developed by Apple Inc. The kit allows for the development of mobile apps on Apple's iOS and iPadOS operating systems. The iOS SDK is a ...

which use the target platform's built-in UI stack. Flutter's control of its rendering pipeline simplifies multi-platform support as identical UI code can be used for all target platforms.

Architecture

The basic component in a Flutter program is a "widget", which can in turn consist of other widgets. A widget describes the logic, interaction, and design of a UI element with an implementation similar to React. Unlike other cross-platform toolkits such as React Native and

Xamarin Xamarin is a Microsoft-owned San Francisco-based software company founded in May 2011 by the engineers that created Mono (software), Mono, Mono (software)#Xamarin.Android, Xamarin.Android (formerly Mono for Android) and Mono (software)#Xamarin.i ...

which draw widgets using native platform components, Flutter renders widgets itself on a per-

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a Raster graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...

basis. Flutter has two types of widgets: ''stateless'' and ''stateful''. Stateless widgets only update if their inputs change, meaning they otherwise won't need to be rebuilt when other elements of the screen change, while stateful widgets can call the setState() method to update an internal state and redraw. Although widgets are the primary method of constructing Flutter applications, they can also be bypassed in favor of directly drawing on a canvas. This feature has been occasionally used to implement game engines in Flutter. The Flutter framework contains two sets of widgets that conform to specific design languages:

Material Design Material Design (codename Quantum Paper) is a design language developed by Google in 2014. Expanding on the "cards" UI that debuted in Google Now, Material Design uses more grid-based layouts, responsive animations and transitions, padding, an ...

widgets implement Google's

design language A design language or design vocabulary is an overarching scheme or style that guides the design of a complement of products or architectural settings, creating a coherent design system for styling. Objectives Designers wishing to give their su ...

of the same name, and ''Cupertino'' widgets implement Apple's

Human interface guidelines Human interface guidelines (HIG) are software development documents which offer application developers a set of recommendations. Their aim is to improve the experience for the users by making application interfaces more intuitive, learnable, and ...

. Flutter allows the developer to use either set of widgets on either platform. Developers can use Cupertino widgets on Android. Flutter apps are written in the Dart language. Release versions of Flutter apps on all platforms use ahead-of-time (AOT) compilation except for on the Web where code is transpiled to

JavaScript JavaScript (), often abbreviated as JS, is a programming language and core technology of the World Wide Web, alongside HTML and CSS. Ninety-nine percent of websites use JavaScript on the client side for webpage behavior. Web browsers have ...

or WebAssembly. Flutter inherits Dart'
Pub

package manager A package manager or package management system is a collection of software tools that automates the process of installing, upgrading, configuring, and removing computer programs for a computer in a consistent manner. A package manager deals wi ...

and

software repository A software repository, or repo for short, is a storage location for Package format, software packages. Often a table of contents is also stored, along with metadata. A software repository is typically managed by source or version control, or rep ...

, which allows users to publish and use custom packages as well as Flutter-specific plugins. The Foundation library, written in Dart, provides basic classes and functions that are used to construct applications using Flutter, such as APIs to communicate with the engine. Flutter's engine, written primarily in C++, provides low-level rendering support using either Google's Skia graphics library or the custom "Impeller" graphics layer, which is enabled by default on iOS and is in beta on Android. The engine interfaces with platform-specific SDKs such as those provided by Android and

to implement features like accessibility, file and network I/O, native plugin support, etc.

History

The first version of Flutter was known as "Sky" and ran on the Android

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

. It was unveiled at the 2015 Dart developer summit with the stated intent of being able to render consistently at 120

frames per second A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (co ...

. On December 4, 2018, Flutter 1.0 was released at the Flutter conference in London. On May 6, 2020, the Dart software development kit ( SDK) version 2.8 and Flutter 1.17.0 were released, adding support for the

Metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

. On March 3, 2021, Google released Flutter 2 during an online Flutter Engage event. It added a

Canvas Canvas is an extremely durable Plain weave, plain-woven Cloth, fabric used for making sails, tents, Tent#Marquees and larger tents, marquees, backpacks, Shelter (building), shelters, as a Support (art), support for oil painting and for other ite ...

-based renderer for web in addition to the HTML-based renderer and early-access desktop application support for

, and

. It also shipped with Dart 2.0 which included support for null-safety. Null safety was initially optional as it was a breaking change and was made mandatory in Dart 3 released in 2023. On May 12, 2022, Flutter 3 and Dart 2.17 were released with support for all desktop platforms as stable. On October 27, 2024, a number of Flutter community developers announced ''Flock'', a fork of Flutter intended to be easier to contribute to while still keeping in sync with all changes made in the upstream code base.

References

{{Google FOSS 2017 software Google software Programming tools Free software programmed in Dart Software frameworks Software using the BSD license .

Architecture

History

See also

References