Offline JWT Payload Decoder Specification

Overview

A high-performance, privacy-focused web utility designed to parse and display the contents of a JSON Web Token (JWT) locally.

Design & Layout

• Color Palette: Professional "Developer-Dark" theme using deep charcoals (#121212), soft grays for text, and subtle syntax highlighting colors (cyan, amber, and light purple) for JSON keys and values.
• Layout:
  • A prominent, full-width text area for pasting the JWT string.
  • A responsive split-view pane appearing after input: Left side for 'Header' and Right side for 'Payload'.
  • A persistent status bar at the bottom indicating 'Secure: Offline Processing Mode Active'.

Interactive Features

1. Instant Parsing: Real-time decoding using a debounce function as the user types or pastes the token.
2. JSON Syntax Highlighting: Auto-formatted JSON display with expandable and collapsible nodes for deep object inspection.
3. Validation Feedback: A status icon (green checkmark or red warning) indicating if the pasted input is a valid-looking JWT string.
4. One-Click Copy: Dedicated buttons for each segment to copy the decoded JSON directly to the system clipboard.
5. Security Privacy Toggle: An optional 'Scrub Sensitive Fields' toggle that automatically filters out standard fields like exp, iat, or custom private claims if configured by the user.

Technical Implementation

• Stack: Pure Vanilla JavaScript or React, leveraging atob() for base64 decoding and JSON.parse() with try-catch blocks for error handling.
• Animations: Subtle fade-in animations for the result containers using CSS transitions to provide a polished, responsive feel.
• Offline Capability: Implementation of a Service Worker to ensure the tool remains fully functional even in an offline environment.