Technical Specification: Free Online Duplicate Line Remover

Overview

A high-performance, browser-based utility designed to identify and remove duplicate lines from large bodies of text. This application prioritizes privacy by performing all operations locally, making it ideal for processing sensitive email lists, configuration files, or logs.

Core Features

• Input Handling: Support for both raw text pasting and .txt / .csv file uploads.
• Configurable Deduplication:
  • Case Sensitivity Toggle: Option to treat 'Apple' and 'apple' as the same or different.
  • Trim Whitespace: Automatically strip leading/trailing whitespace before comparison.
  • Sorting Options: Toggle between "Preserve Original Order" and "Sort Alphabetically".
• Statistics Panel: Displays total lines, unique lines, and count of removed duplicates in real-time.
• One-Click Export: Ability to download the processed result as a .txt file.
• Clipboard Sync: Quick copy-to-clipboard button with status feedback.

User Interface Design

• Style: Professional, clean, light-mode only aesthetic. Use high-contrast typography (Inter/Roboto font stack).
• Palette: White/Light Gray background (#F8FAFC), Primary Action: Indigo (#4F46E5), Success/Stats: Emerald (#10B981).
• Layout:
  • Header: Simple tool title and descriptive sub-header.
  • Main Area: A split-screen responsive layout (or stacked on mobile) featuring a large input area on the left/top and a results/preview area on the right/bottom.
  • Control Bar: A floating, docked, or top-aligned panel containing all operational toggles (checkboxes, select inputs).
  • Feedback: Soft-transition progress indicator for large operations.

Interaction & Animations

• Micro-interactions: Use subtle CSS transition: all 0.2s ease for button hover states and state changes.
• Loading States: Replace standard browser loaders with smooth, CSS-based spinners within the action buttons.
• Feedback: When "Copy to Clipboard" is clicked, show a temporary success indicator (tooltip/toast).

Developer Constraints & Requirements

• Architecture: Single-file HTML structure. All CSS and JS must be embedded.
• Storage: NO localStorage, sessionStorage, or cookies. Maintain state purely in JS variables.
• Compatibility: Ensure full functionality within a sandboxed <iframe> environment.
• Interactivity: Use pure Vanilla JS for all logic. No external frameworks (e.g., React, Vue).
• Performance: Use efficient array manipulation (e.g., Set object for $O(n)$ time complexity on deduplication) to ensure performance on large files.
• External Assets: Use CDN links for Tailwind CSS (for layout) and Lucide Icons (for iconography).