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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Devin Desktop
Devin Desktop (formerly Windsurf) is an AI-powered development environment that combines a full-featured IDE with advanced coding agents in a unified workspace. Formerly known as Windsurf, the platform enables developers to manage local and cloud-based AI agents, delegate tasks, review code, and ship software without leaving their editor. Developers can use multiple coding agents simultaneously to research, write, test, debug, and improve code while maintaining full visibility into every change. Devin Desktop includes features such as agent orchestration, shared workspaces, intelligent code completion, contextual code search, and integrated review tools. The platform supports a wide range of models, extensions, language servers, and MCP integrations, allowing teams to work with their preferred tools and workflows. Devin Desktop helps engineering teams accelerate software development, improve productivity, and manage AI-assisted coding at scale.
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Replit
Replit is an AI-powered app development platform that helps users turn ideas into websites, mobile apps, designs, slides, animations, data visualizations, games, documents, and spreadsheets without needing to code manually. The platform features Agent 4, which can interpret prompts, plan requirements, write production-ready code, evolve projects, and publish apps. Replit includes Infinite Canvas for visually exploring and tweaking designs before applying them directly to an app. Parallel Agents let multiple tasks run at once, helping teams build authentication, databases, design, and other features faster. Built-in infrastructure includes authentication, database, hosting, monitoring, AI integrations, and connections to services such as OpenAI, Stripe, and Google Workspace. Built for individuals, teams, and enterprises, Replit helps users prototype, collaborate, launch, and scale software from one workspace.
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Posit
Posit builds tools that help data scientists work more efficiently, collaborate seamlessly, and share insights securely across their organizations. Its Positron code editor provides the speed of an interactive console combined with the power to build, debug, and deploy data-science workflows in Python and R. Posit’s platform enables teams to scale open-source data science, offering enterprise-ready capabilities for publishing, sharing, and operationalizing applications. Companies rely on Posit’s secure infrastructure to host Shiny apps, dashboards, APIs, and analytical reports with confidence. Whether using open-source packages or cloud-based solutions, Posit supports reproducible, high-quality work at every stage of the data lifecycle. Trusted by millions of users—and more than half of the Fortune 100—Posit empowers professionals across industries to innovate with data.
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