JSON / XML Formatter

Format, highlight and compare JSON, XML and Markdown, with mermaid diagram rendering

A lightweight Chrome extension for formatting, highlighting, and comparing JSON, XML, and Markdown — including mermaid diagrams. Everything is processed locally in your browser: your data is never uploaded, there is no analytics and no third-party service. FORMATTING • Format — structured output with indentation and syntax highlighting • Minify — single line, no whitespace • JSON Tree Collapsing — expand/collapse objects and arrays with visual connectors • Error Handling — pinpoints the exact error character with context and hints • Save & Copy — save formatted output to a file or copy to clipboard • Adjustable font size (A− / A+) MARKDOWN • .md files open rendered instead of raw text — from any site or from your disk • Mermaid diagrams: flowchart, sequence, ER, state, class, pie • Fullscreen diagram viewer — wheel scrolls, Ctrl+wheel zooms, drag pans • Syntax highlighting inside code fences • Copy button on every code block • Preview / Source toggle COMPARE MODE • Two panels with character-level diff and navigation between changes • Synchronised scrolling, LCS-based algorithm • Works for JSON, XML, Markdown and plain text CONVENIENCE • Drag a .md, .json or .xml file onto the tab — it opens formatted • Select JSON/XML on any page → right-click → "Format in JSON/XML Formatter" • Automatic formatting when the browser opens a JSON, XML or Markdown URL The extension bundles one third-party library — mermaid (MIT licence) — for diagram rendering. It ships inside the package and is loaded from disk, only when a document actually contains a diagram. Nothing is ever fetched from a CDN, and no document you open is sent anywhere.