Free Online SHA-256 and SHA-512 File Checksum Validator

Overview

A privacy-focused, client-side utility designed to calculate and verify the cryptographic integrity of files. This tool is built entirely within a single HTML file using the Web Crypto API, ensuring zero server-side interaction and total user privacy.

Core Features

• Algorithm Support: Select between SHA-256 and SHA-512 hashes.
• Drag-and-Drop: Intuitive file input area that accepts drag-and-drop operations.
• Integrity Verification: An optional input field allows users to paste a reference hash to instantly compare against the calculated hash.
• Visual Feedback: Color-coded status indicators (Success/Failure) for hash matching.
• Progress Tracking: A progress bar provides feedback when hashing larger files.
• Zero-Latency Copy: One-click functionality to copy the generated hash to the clipboard.

Technical Architecture

• Processing: Uses crypto.subtle.digest via the Web Crypto API.
• State Management: All application states (file data, hash results, comparison hashes) are stored in local variables. No use of localStorage, sessionStorage, or cookies is permitted.
• Responsiveness: Fluid grid layout built with Tailwind CSS, ensuring accessibility on desktop, tablet, and mobile browsers.
• Security: CSP-compliant. No external script dependencies outside of reliable, integrity-checked CDNs.

UI/UX Design

• Aesthetic: Clean, professional "SaaS" aesthetic. Light mode only, utilizing a professional color palette: White background (#FFFFFF), soft gray surfaces (#F9FAFB), and a vibrant primary brand blue (#2563EB) for interactive elements.
• Typography: Modern sans-serif stack (Inter or System UI) for maximum readability.
• Animations: Subtle transitions for hash result appearance and success/failure state changes using CSS transitions (ease-in-out).

Developer Directives

1. Single File Constraint: All CSS and JS must be embedded within the main index.html. No external build processes.
2. Storage Prohibition: You must not attempt to save any user data. Any attempt to write to local/session storage will trigger an error.
3. Sandboxed Compatibility: The app must function perfectly inside an iframe with a null origin. Use standard window event listeners and avoid any operations that require cross-origin access.
4. Accessibility: Ensure all inputs, buttons, and status messages are fully accessible to screen readers using appropriate ARIA labels.
5. Responsive Layout: The design should adapt seamlessly to small screens, specifically ensuring that the hash strings wrap correctly and the file upload zone remains reachable.