The term "code preview" refers to a functionality within development environments or web-based editors that allows developers to see a visual or functional representation of source code while writing it. The purpose of code preview is to provide immediate feedback on the structure or output of the code—such as layout previews (e.g., for HTML/CSS), live output rendering, or syntax highlighting. Code previews help accelerate development, prevent errors early, and contribute to software quality assurance.
Live Preview: Real-time display of code changes, especially for front-end code such as HTML, CSS, and JavaScript.
Syntax Highlighting: Color-coded display of code elements such as commands, variables, and comments for better readability.
Render Preview: Display of graphical outputs (e.g., in UI design tools or for PDF/Markdown rendering).
Real-time Error Highlighting: Visual marking of syntax or compilation errors while typing.
Component or Module Preview: Visualization of UI components (e.g., in React, Angular, Vue) during development.
Version Comparison Preview: Display of code changes compared to previous versions or branches.
Markdown/Documentation Preview: Display of formatted output of documentation or README files written in Markdown.
A developer sees the layout of a website in a preview window while editing HTML and CSS.
A Markdown editor shows a formatted view of the documentation as it is written.
A JavaScript developer uses a tool like CodePen to test and visualize functions live.
In an IDE like Visual Studio Code, syntax errors are underlined in red as the developer types.
A UI designer works in a framework like Storybook and immediately sees how a new component will look in the frontend.