JSFiddle
JSFiddle has the notion of panels (or tabs if you switch into the tabbed layout), there are 4 panels, 3 where you can enter code, and 1 to see the result: HTML - structure code, no need to add body doctype head, that's added automatically, CSS - styles. You can switch pre-pocessor to SCSS, JavaScript - behavior. There are many frameworks and code pre-processors you can use. Once you enter code, just hit "Run" in the top actions bar, and the fourth panel with results will appear. SFiddle allows you to switch the layout of the editor from the classic 2x2 grid to something that suits your needs. In addition to the grids mode it also has a tabbed mode. Grids are fully resizable. As an addition resizing the Results panel will tell you its width (handy for working on media queries).
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AWS Cloud9
AWS Cloud9 is a cloud-based integrated development environment (IDE) that lets you write, run, and debug your code with just a browser. It includes a code editor, debugger, and terminal. Cloud9 comes prepackaged with essential tools for popular programming languages, including JavaScript, Python, PHP, and more, so you don’t need to install files or configure your development machine to start new projects. Since your Cloud9 IDE is cloud-based, you can work on your projects from your office, home, or anywhere using an internet-connected machine. Cloud9 also provides a seamless experience for developing serverless applications enabling you to easily define resources, debug, and switch between local and remote execution of serverless applications. With Cloud9, you can quickly share your development environment with your team, enabling you to pair program and track each other's inputs in real time.
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Replit
Use our free, collaborative, in-browser IDE to code in 50+ languages — without spending a second on setup. Start coding with your favorite language on any platform, OS, and device. Invite your friends, teammates, and colleagues right into your code with Google-docs like editing. Import, run, and collaborate on millions of GitHub repos with 0 manual setup. From Python, to C++, to HTML and CSS, stay in one platform to learn and code in any language you want. The second you create a new repl, it's instantly live and sharable with the world. Learn how to code from 3 million+ passionate programmers, technologists, creatives, and learners of all kinds. Make your team more productive with interactive docs, real-time collaboration, and 0-hassle remote interviewing. Create apps programatically, spin up bots and customize the IDE with plugins to fit your needs.
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Visual Studio
Microsoft Visual Studio is the industry-leading integrated development environment (IDE) for building modern applications across desktop, mobile, cloud, and web. It empowers developers to write, refactor, debug, test, and deploy software faster with intelligent assistance powered by GitHub Copilot and AI-driven workflows. With Agent Mode, developers can automate repetitive coding tasks, optimize performance, and receive contextual help directly in the IDE. The suite includes Visual Studio 2022, the comprehensive IDE for .NET and C++ development on Windows, and Visual Studio Code, the lightweight, cross-platform editor supporting JavaScript, Python, and dozens of other languages. Visual Studio integrates seamlessly with Azure, GitHub, and CI/CD pipelines, enabling teams to collaborate and ship code efficiently. Trusted by millions worldwide, Visual Studio provides the tools and intelligence developers need to build reliable, scalable, and secure applications from concept to release.
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