Unified Diff MCP Server
MCP ServerFree** - Beautiful HTML and PNG diff visualization using diff2html, designed for filesystem edit_file dry-run output with high-performance Bun runtime.
Capabilities6 decomposed
unified diff visualization with html rendering
Medium confidenceConverts unified diff format (standard patch output from git, diff tools, or filesystem operations) into interactive HTML visualizations using the diff2html library. The server parses unified diff syntax, tokenizes line-by-line changes (additions, deletions, context), and renders them as side-by-side or inline HTML with syntax highlighting and line numbering. Built on Bun runtime for fast parsing and rendering without Node.js overhead.
Purpose-built as an MCP server specifically for filesystem edit_file dry-run output, integrating diff2html rendering directly into the MCP tool-calling protocol rather than as a standalone utility. Uses Bun runtime for sub-100ms diff parsing and rendering, avoiding Node.js startup overhead in agent workflows.
Faster than web-based diff viewers (GitHub, GitLab) for local agent workflows because it renders diffs in-process without network round-trips, and more integrated than standalone diff2html CLI tools because it exposes diff visualization as a callable MCP tool.
png diff image generation from unified diffs
Medium confidenceConverts unified diff format into rasterized PNG images by first rendering HTML via diff2html, then using a headless browser or image rendering engine to capture the visualization as a static image file. This enables embedding diff previews in chat interfaces, emails, or documentation without requiring HTML rendering capability on the client side.
Integrates headless rendering into the MCP server itself, allowing agents to request PNG diffs directly without spawning external processes or managing temporary files — the server handles the full pipeline from diff parsing to image output.
More convenient than chaining separate tools (diff2html CLI + Puppeteer) because it's a single MCP call, and produces better visual fidelity than ASCII-art diffs because it preserves syntax highlighting and layout in the rasterized output.
mcp tool registration for diff operations
Medium confidenceExposes diff visualization as a callable MCP tool with a standardized schema, allowing MCP clients (Claude Desktop, Cline, etc.) to invoke diff rendering as part of their tool-calling workflow. The server implements the MCP tool protocol, accepting diff input through the standard tool arguments interface and returning results in MCP-compatible format (text, image URIs, or embedded base64 data).
Implements the full MCP server lifecycle (initialization, tool registration, result serialization) specifically for diff visualization, allowing seamless integration into agent workflows without requiring clients to manage subprocess calls or file I/O.
More ergonomic than exposing diff rendering as a CLI tool because MCP clients can call it directly with structured arguments, and more flexible than hardcoding diff visualization into a single agent because it's a reusable server that any MCP client can consume.
filesystem edit dry-run diff extraction
Medium confidenceParses and visualizes diffs generated from filesystem edit operations (e.g., file_edit tool dry-run output), extracting the unified diff format from edit tool responses and rendering them for human review before applying changes. This capability bridges the gap between LLM-generated edits and visual verification, allowing agents to show users exactly what will change before committing.
Specifically designed for the MCP edit_file dry-run workflow, where agents generate changes and need to show them to users before applying. The server integrates directly into this pattern, consuming dry-run output and rendering it without requiring additional parsing or transformation.
More integrated than generic diff viewers because it understands the edit_file dry-run pattern, and more useful than raw diff output because it provides visual feedback that non-technical users can understand.
high-performance diff parsing with bun runtime
Medium confidenceLeverages Bun's JavaScript runtime (which includes native TypeScript support, faster module loading, and optimized string handling) to parse unified diff format with minimal latency. The server uses Bun's built-in performance characteristics to achieve sub-100ms parsing times for typical diffs, avoiding Node.js startup overhead and garbage collection pauses that would impact agent responsiveness.
Chooses Bun as the runtime specifically for diff parsing performance, avoiding Node.js startup overhead and leveraging Bun's faster module loading and string handling. This is a deliberate architectural choice to minimize latency in agent workflows where diff visualization is called frequently.
Faster than Node.js-based diff servers for typical agent workflows because Bun has lower startup overhead and faster string parsing, though the difference is only significant for high-frequency calls (>10/second).
side-by-side and inline diff layout rendering
Medium confidenceRenders unified diffs in multiple visual formats using diff2html: side-by-side layout (original and modified code in adjacent columns) and inline layout (changes marked within a single code block). The server supports both formats and allows clients to specify their preference, enabling different use cases (detailed review vs. compact summary).
Exposes diff2html's layout options as configurable MCP tool parameters, allowing clients to request their preferred visualization format without requiring server-side configuration changes.
More flexible than fixed-layout diff viewers because it supports both side-by-side and inline formats, and more user-friendly than CLI diff tools because the layout choice is explicit and easy to change per request.
Capabilities are decomposed by AI analysis. Each maps to specific user intents and improves with match feedback.
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Best For
- ✓Developers using MCP-compatible tools (Claude Desktop, Cline, etc.) for file editing workflows
- ✓Teams automating code generation with visual change verification
- ✓LLM agents performing filesystem edits with dry-run validation
- ✓Chat-based AI agents that need to communicate diffs visually
- ✓Documentation systems that embed change previews
- ✓Teams sharing diffs across platforms without HTML support
- ✓Developers building MCP servers that need diff visualization
- ✓LLM agents performing file edits with verification steps
Known Limitations
- ⚠Requires valid unified diff format input — malformed diffs will fail parsing
- ⚠HTML output size scales linearly with diff size; very large diffs (>100MB) may cause memory pressure
- ⚠No built-in syntax highlighting for languages beyond what diff2html supports natively
- ⚠PNG rendering adds latency (~500ms-2s per diff) compared to HTML-only output
- ⚠Large diffs produce large PNG files; no built-in compression or pagination
- ⚠PNG output is static — no interactivity like HTML (no line selection, copy-paste)
Requirements
Input / Output
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** - Beautiful HTML and PNG diff visualization using diff2html, designed for filesystem edit_file dry-run output with high-performance Bun runtime.
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