Text Diff Checker

WHAT IT DOES

This tool compares two texts and displays the differences side by side in a clear, color-coded format. It supports line-level, character-level, and word-level diff modes, so you can see exactly what changed—whether you're comparing code, documents, or plain text. Added content is highlighted in green, removed content in red, and unchanged content remains neutral. The tool also shows statistics: how many lines/characters/words were added, removed, or unchanged. You can paste text directly from the clipboard into either field, and the diff updates automatically as you type.

WHERE IT RUNS

Runs on any website—no per-site configuration needed. Works entirely in the browser, so your text never leaves your machine. The panel can be opened on any page, making it a convenient tool for developers, writers, editors, and anyone who needs to compare text quickly.

HOW TO USE

Install the userscript via BotGentz, then open the panel. Enter your original text in the "Text 1" field and your modified text in "Text 2" field. The diff updates automatically as you type, or you can click "Compare Texts" to refresh. Choose the diff mode from the dropdown: "Line-level diff" shows whole lines that were added or removed, "Character-level diff" highlights individual character changes within lines, and "Word-level diff" shows word-by-word differences. Use "Copy Diff Result" to copy the entire diff output to your clipboard. "Clear All" resets both text fields.

TECHNICAL MECHANISM

The tool implements a custom diff algorithm that works at three granularities. For line-level diff, it splits both texts by newline and performs a longest common subsequence (LCS)-style comparison with lookahead to detect swapped lines. For character and word-level diff, it splits the text into individual characters or words and compares them sequentially, marking insertions and deletions as it goes. The algorithm is optimized for typical text sizes found in user input—it handles documents up to several thousand lines efficiently. The output is rendered using semantic HTML with CSS classes for added, removed, and unchanged content, avoiding inline styles and ensuring consistent theming with the BotGentz panel. The tool respects PLAYBOOK-A §6 rule 3 by never using innerHTML with page-derived text; all user text is escaped before rendering.

THE PANEL

The floating panel is built with BotGentz's BGPanel framework. It is draggable—click and drag the panel header to reposition it anywhere on the screen. The panel remembers its position per site via the settings dropdown. It can be collapsed to a small bubble icon by clicking the minimize button, preserving screen space. The panel can be closed and reopened via the BotGentz toolbar. Press the Escape key to quickly close the panel. The panel automatically adjusts its layout for different screen sizes.

PLEASE NOTE

Requires the free BotGentz extension. This tool processes text entirely in your browser and does not send any data to external servers. Text is not stored or logged anywhere—only your settings are saved locally via GM_setValue. The diff algorithm is designed for moderate-sized texts; very large documents (10,000+ lines) may take a few seconds to process. Websites change frequently; if the tool stops working on a particular site, the script may need updating.