Supported Languages & Formats

UniPreview supports 23 languages and formats, plus a plain-text fallback for anything else (24 selectable options in total).

Core web (inline preview)

HTML, CSS, JavaScript, TypeScript render inline and update live as you edit - the standard HTML/CSS/JS playground experience, with TypeScript transpiled in the browser.

Frameworks & components (inline preview)

React JSX, React TSX, Vue 3 (SFC), Svelte components preview inline without a build step or project scaffold.

Preprocessors & templating (inline preview)

SCSS, Sass, LESS, Pug compile in the browser before rendering. Tailwind CSS utility classes used inside HTML or JSX are also detected and rendered automatically via the Tailwind CDN build - it is a rendering feature rather than a separate language option.

Data, markup & query formats (inline preview)

JSON, XML, YAML, SQL, Markdown render with syntax highlighting and a formatted view. SQL runs against an in-browser SQLite engine.

Runtimes (inline, via WebAssembly)

Python runs with Pyodide and PHP runs with php-wasm - both execute entirely in your browser, not on a server.

External preview languages

Dart, Flutter and Angular need a full compiler that cannot run in a plain browser frame. UniPreview shows the code with syntax highlighting and, once you opt in to external previews in Settings, a "Run on DartPad" or "Run on StackBlitz" button that opens the real compiler (DartPad, Zapp, or StackBlitz). XAML is grouped alongside them and shown with syntax highlighting. This is intentional routing to the right renderer rather than a limitation - some languages genuinely need a native toolchain UniPreview does not try to replicate in-browser.