Diff Checker

Online diff checker to compare text, code and files side by side. Syntax highlighting, Prettier formatting, and AI diff summaries

🔒 Your Data Stays Private Diff Checker is a diff checker software that runs entirely in your browser. No uploads to third-party servers. No data logging. Your text, code, and files never leave your device. 🛠 Diff Checker Software — Powered by Monaco Editor Compare text, code, and files side by side with real-time editing. Built on Monaco Editor — the same engine behind VS Code — with syntax highlighting for 17+ languages and instant change detection. This online diff checker is designed for developers, testers, writers, and anyone who needs fast, accurate diff check. 🌟 Key Features 📝 Real-Time Diff Editor — edit and compare simultaneously, changes highlight as you type. No need to click any button — diff check happens instantly. 💻 Code Diff Check — syntax highlighting for 17+ popular programming and markup languages. Automatic language detection ensures the right highlighting every time. 📁 File Diff Checker — upload and compare plain text files, code files, and Office documents (Word, Excel, PowerPoint). Supports files up to 50 MB per side. 🌐 JSON Diff Checker — identify structural and data differences in JSON files. Normalize and sort keys for clean, readable comparison. Perfect for API testing and json diff check. 🎨 Code Formatting — auto-format code with Prettier before comparing. Supports 20+ languages to ensure consistent formatting so you only see meaningful changes. 📄 Text Diff Checker — compare any text: documents, configuration files, logs, data exports, clipboard content, or any plain text. Works as a text diff checker for all your comparison needs. 🔗 Compare Browser Tabs — select two open tabs in your browser to instantly load and compare their source code or text side by side. Great for checking differences between staging and production pages. 🤖 AI-Powered Summaries — generate intelligent diff summaries using OpenAI API. Choose between full text analysis or diff-only mode for focused insights. Requires your own API key. 💾 Comparison History — auto-saves your comparisons locally using IndexedDB. Browse, restore, or delete past sessions anytime. Up to 50 comparisons stored, 10 MB each. 🔀 Revert Changes — one-click revert icons on each change block let you quickly undo individual modifications, just like in JetBrains IDEs. ⚙️ Diff Algorithms 🔬 Smart Diff — advanced algorithm for accurate, context-aware change detection ⬜ Ignore Whitespace — focus on meaningful changes only, skip leading and trailing spaces 📐 Classic LCS — traditional longest-common-subsequence algorithm for straightforward comparison ⚡ Auto-switch — automatically uses fast algorithm for files over 10 MB to prevent slowdowns 🎯 View Modes 📊 Split View — side-by-side comparison with synchronized scrolling 📋 Unified View — inline diff showing changes in a single column 🔍 Show Diff Only — collapse unchanged regions to focus on what changed 📱 Auto Layout — automatically switches to unified view when the window is too narrow 🚀 How It Works 1. Open the Diff Checker extension 2. Paste, type, or upload two versions of text or code 3. View highlighted differences instantly — no extra clicks needed 4. Edit directly in the diff view — changes update in real time 5. Use toolbar actions: format code, normalize JSON, swap sides, or copy diff 6. Optional: generate AI-powered summary of your changes 🎨 Use Cases 👨‍💻 Software Development — code diff checker for comparing source code versions with full syntax highlighting. Review pull requests, debug regressions, and track modifications across branches. 🌐 Web Development — compare HTML, CSS, and JavaScript files. Identify what changed between deployments or design iterations. 📊 API Testing — json diff checker to compare API responses, detect schema changes, and validate data transformations. Normalize JSON keys for clean structural comparison. 📚 Document Review — text diff checker for contracts, legal documents, reports, and technical writing. Spot every change between drafts and final versions. ⚙️ DevOps & SysAdmin — compare configuration files, server settings, environment variables, and deployment scripts. File diff checker for nginx configs, Docker files, and CI/CD pipelines. 📈 Data Analysis — csv diff checker for comparing spreadsheet exports, database dumps, and data migration results. 🔄 Version Control — check diff between file versions before committing. Compare local changes against repository versions. 🎓 Education — review student submissions, compare assignment versions, and provide feedback on code changes. ✍️ Content Editing — compare drafts and published versions of articles, blog posts, and documentation. 🔬 Scientific Research — analyze differences in experiment configurations, data sets, and research papers. 💼 Legal & Compliance — compare contract versions, policy documents, and regulatory filings to track every modification. 🎉 Benefits ⏱ Time Savings — instantly find changes with diff check online, eliminating manual line-by-line comparison 🎯 Enhanced Accuracy — highlights every difference with color coding: green for additions, red for deletions 🤖 AI Insights — get intelligent summaries explaining what changed and why it matters 🎨 Clean Comparison — format and normalize text before comparing to eliminate noise 📁 Multi-Format — compare text, code, structured data, and Office documents 🔒 Complete Privacy — all processing happens locally, your data never leaves your browser 🌐 Works Offline — no internet required for comparisons (AI features need connection) 💡 Familiar Interface — Monaco Editor provides the same experience as VS Code ❓ Frequently Asked Questions 🕵️ How does Diff Checker work? It uses Monaco Editor (the VS Code engine) to compare two versions of text or code. The diff algorithm analyzes both inputs and highlights additions, deletions, and modifications in real time. 🛠 Do I need an internet connection? No. Diff Checker works entirely offline in your browser for all comparison features. Only AI-powered summaries require an internet connection and your own OpenAI API key. 🔒 Is my data stored or sent to a server? No. All text comparing happens locally on your device. The extension does not log, store, or transmit your data. AI features optionally send data to OpenAI only when you explicitly enable them. 🤖 How do AI summaries work? AI summaries use OpenAI API to analyze your diffs and provide intelligent insights about what changed. You provide your own API key, choose your preferred model, and select between full text analysis or diff-only mode. This feature is completely optional. 📁 What file formats can I compare? Plain text files, code files in 17+ languages, and Office documents (Word, Excel, PowerPoint). 💻 Can I use code diff check for different programming languages? Yes. Code diff check supports 17+ programming languages with full syntax highlighting and automatic language detection. 📊 How does JSON diff check work? JSON diff check compares two JSON structures, detecting differences in keys, values, and nested objects. You can normalize and sort JSON keys before comparison for cleaner results. This is useful for API testing, database management, and configuration comparison. 🔍 Does it work with large files? Yes. Diff Checker handles files up to 50 MB per side. For files over 10 MB, it automatically switches to a faster diff algorithm to maintain performance. 📝 Can I edit text while comparing? Yes. Both the original and modified panels are editable. Changes are highlighted in real time as you type. You can also revert individual changes with one click. 💾 Does it save my comparisons? Yes. Diff Checker automatically saves your comparisons to local storage (IndexedDB). You can browse, restore, or delete past sessions from the History panel. Up to 50 comparisons are stored, with a maximum of 10 MB each. 🎨 Can I format code before comparing? Yes. The Format button uses Prettier to auto-format code in 20+ languages before comparison, eliminating formatting noise and showing only meaningful changes. 🔗 How do I compare browser tabs? Click Compare Tabs Source in the toolbar, select two open browser tabs, and the extension will load and compare their source code side by side. 🔒 Privacy Local Data Processing: All comparisons are performed directly on your computer. Your sensitive information — code snippets, confidential documents, API responses — never leaves your local environment. No Data Logging: The extension does not log, store, or transmit any of your input data. We have no access to what you compare, and we do not keep any records of your activity. Enhanced Security: By operating locally, Diff Checker minimizes the risk of data breaches and unauthorized access. You can use the extension with confidence, knowing that your information is safe. AI Privacy: When using AI features, data is sent to OpenAI only when you explicitly enable this feature and provide your API key. This is completely optional and under your control. We believe privacy is a fundamental right. With Diff Checker, you can compare text and code with peace of mind, knowing your information remains entirely under your control. 📋 Technical Details 🖥 Monaco Editor (VS Code engine) with real-time editing and diff computation 🎨 Prettier integration for code formatting (20+ languages) 📂 Office file support (Word, Excel, PowerPoint) 💾 IndexedDB-based history storage (50 comparisons max, 10 MB each, 500 MB total) 📦 Supports files up to 50 MB per side 🌗 Dark and light themes with automatic detection 📡 Works offline for all comparison features 🔤 UTF-8, ASCII, and multi-byte character support 🔍 Automatic language and file format detection 🚀 Get Started Today! Install Diff Checker and experience effortless text and code comparison. Whether you need to check diff between two files, compare code snippets, review JSON structures, or analyze browser tab source code — this diff checker online tool has you covered. Optionally enhance your workflow with AI-powered insights.