Diffs, from The Pierre Computer Co., is a highly flexible, open-source library designed for rendering code files and diffs on the web. Built on top of Shiki for robust syntax highlighting, the library provides both high-level components for quick integration and low-level APIs for advanced customization. It is architected to be highly performant, utilizing browser-native capabilities like Shadow DOM and CSS Grid to ensure efficient rendering with minimal DOM overhead. Whether you are building an interactive code review interface, an AI-assisted coding platform, or simply need to display code snippets, Diffs offers the necessary primitives to handle file comparisons, patch visualization, and even merge conflict resolution.

The library is designed to be framework-agnostic at its core, rendering raw HTML strings that are then consumed by higher-order components. This allows for seamless integration into React applications through specialized components, as well as providing a powerful vanilla JavaScript API. It supports sophisticated features such as virtualization for large codebases, custom token hooks for interactivity, and a worker pool system to offload syntax highlighting tasks, preventing main-thread jank during intensive rendering operations.

Some of the key features are:

• Flexible Layouts: Choose between stacked or split diff views, with support for line wrapping, line numbering toggles, and customized hunk separators.
• Adaptable Theming: Automatically integrates with any Shiki theme, allowing for consistent appearance across light and dark color modes.
• Interactive Hooks: Supports token-level callbacks, allowing developers to implement hover tooltips, LSP-style interactions, or custom UI elements directly on syntax-highlighted code.
• Advanced Annotations: Provides a powerful framework for injecting line-specific comments, CI annotations, and custom UI components into code views.
• Worker Pool Architecture: Offloads heavy syntax highlighting tasks to background threads to ensure smooth performance even when handling large files or massive diff sets.
• SSR & Hydration: Includes comprehensive utilities for server-side rendering and client-side hydration, perfect for performance-sensitive applications.
• Merge Conflict Resolution: Features a dedicated primitive to visualize and resolve merge conflicts with built-in or custom UI logic.
• Rich Customization: Allows for deep styling control through CSS variables, custom headers, and the ability to inject custom CSS into the Shadow DOM.

Developers can get started with the library by importing the relevant packages for their framework of choice. The library provides clear entry points for vanilla JS, React, and server-side utilities, ensuring that users can leverage the specific functionality needed for their project. With support for both parsing raw file pairs and standard unified patch strings, Diffs is highly adaptable to various data sources, including Git outputs or generative AI snapshots. Additionally, the library includes a theme system compatible with other modern editors like VS Code, Cursor, and Zed, simplifying the process of maintaining a unified visual identity across tools.

Some common use cases include:

• Interactive Code Review: Building rich interfaces for reviewing pull requests with support for line-level comments and interactive diff acceptance.
• Documentation & Blogs: Rendering syntax-highlighted code snippets and diffs in documentation sites with high-performance SSR.
• AI-Assisted Coding Tools: Creating code editors that can handle streaming diffs and provide real-time UI for accepting or rejecting AI-suggested changes.
• Large File Visualization: Displaying massive source files or long-running diffs in a single scrollable container using virtualized rendering.
• Merge Conflict UI: Implementing dedicated conflict resolution screens that allow users to select current, incoming, or both changes in a structured way.