Best Free Developer Tools 2025: The Essential List

Best Free Developer Tools 2025: The Essential List Every developer needs a solid toolkit, and in 2025, there's no excuse to pay for tools that your browser can handle for free. This is the definitive list of the best free developer tools — tested and organized by category. No logins. No subscriptions. Just tools that work. Code Formatting and Linting Prettier Playground Run Prettier directly in your browser. Paste messy JavaScript, TypeScript, CSS, or HTML and get properly formatted output instantly. Best for: Quick formatting without setting up a local config file. ESLint Demo The official ESLint playground lets you test rules and see exactly which parts of your code trigger violations — useful for learning new lint rules. JSON Formatter A clean formatter for JSON: paste a minified blob, get readable indented output with syntax highlighting and error detection. // Before { "name" : "Alice" , "age" : 30 , "city" : "Taipei" } // After formatting { "name" : "Alice" , "age" : 30 , "city"