Technical Specification: Free Online HTTP Request Headers Viewer

1. Overview

A client-side web application designed to instantly display the HTTP request headers sent by a browser. This tool acts as an echo client, fetching header data from a public echo service and presenting it in a clean, human-readable format for developers and curious users.

2. Core Features

• Automatic Header Inspection: Upon interaction, the app makes an asynchronous fetch() request to a public echo endpoint (e.g., https://httpbin.org/headers) and parses the returned JSON object into the UI.
• Formatted & Raw Views: Users can toggle between a formatted, easy-to-read list and a raw JSON/Text output.
• One-Click Copy: Dedicated buttons to copy specific headers or the entire request set to the system clipboard.
• Educational Tooltips: Hoverable labels that provide brief descriptions of common headers (e.g., "What is User-Agent?").
• Responsive Interface: Fully optimized layout for mobile, tablet, and desktop screens.

3. UI/UX Specification

• Layout:
  • Header: Simple, clear title block centered on the page.
  • Control Bar: A prominent "Inspect Headers" call-to-action button, styled with a high-contrast blue background.
  • Results Area: A card-based layout featuring a clean table for header keys and values. Values are color-coded slightly to distinguish them from keys.
• Color Palette (Light Mode Only):
  • Background: #F9FAFB (Subtle off-white).
  • Card Surface: #FFFFFF (Pure white with soft shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1)).
  • Primary Accent: #2563EB (Professional SaaS Blue).
  • Text: #1F2937 (Dark Gray) for readability.
  • Border/Dividers: #E5E7EB (Light Gray).
• Animations:
  • Smooth fade-in (opacity: 0 to 1) for result cards when they appear.
  • Micro-interactions on buttons (slight scale down on click, subtle background shift on hover).

4. Technical Constraints & Directives

• Single File Architecture: All logic (Vanilla JS), structure (HTML5), and styling (CSS3/Tailwind CDN) must exist within one HTML file.
• Storage Blocked: Use in-memory state only. No localStorage, sessionStorage, or cookies allowed. Any UI state (like "results") must be stored in JS variables.
• Iframe Compatibility: The app must function within a sandboxed iframe. Ensure no popups (alert, prompt) are used; implement custom modal overlays if user feedback is needed.
• Security: Use target="_blank" rel="noopener noreferrer" for any external links. Ensure all Fetch requests use standard HTTPS endpoints.
• No Branding: Ensure no fictional logos, brand names, or watermarks. The tool is purely functional.