Long Sentence Highlighter

WHAT IT DOES

Long Sentence Highlighter is a browser extension that scans any webpage for sentences that exceed a user-defined word count threshold and highlights them with a colored background and underline. By default, sentences of 30 words or more are highlighted, but you can adjust this threshold from 5 to 200 words to suit your preferences. The tool displays a running count of long sentences found on the page, helping writers, editors, students, and content creators identify complex or overly lengthy sentences that may reduce readability. Long sentences often indicate opportunities to improve clarity by splitting into shorter, more digestible phrases. The tool is ideal for editing blog posts, articles, academic papers, documentation, and any other text-based content where sentence length matters.

WHERE IT RUNS

Long Sentence Highlighter works on any webpage that contains English text. It runs locally in your browser as a lightweight userscript, scanning text nodes across the entire page while avoiding script tags, style blocks, and form inputs. It works on blog posts, news articles, documentation pages, email drafts, social media posts, academic papers, creative writing, and any other text-based content. The tool handles static pages, dynamically loaded content via AJAX, and single-page applications where content updates without page reloads. All processing occurs entirely in your browser—no text is ever sent to any server.

HOW TO USE

After installation, open the floating panel by clicking the extension icon. The panel displays the current count of long sentences found on the page and shows the current word threshold. To adjust the threshold, enter a new number in the input field (5 to 200 words) and click Apply. The page will automatically rescan with the new threshold. Toggle highlighting on or off using the checkbox—when enabled, long sentences appear with a red background and red underline, making them instantly visible. Click the Scan Page button to manually trigger a fresh scan, useful after content updates. Click Clear Highlights to remove all highlighting without disabling the feature permanently. The tool automatically scans the page when it loads if highlighting is enabled, and continues to detect new content as it appears. The count updates in real time as you scroll and interact with the page. Hover over a highlighted sentence to see its exact word count in a tooltip.

REAL MECHANISM — WHY THIS WORKS

Most readability tools rely on cloud-based natural language processing or complex grammatical parsers to identify sentence boundaries, which introduces latency, privacy concerns, and dependency on external services. Long Sentence Highlighter uses a different approach: it runs a deterministic sentence segmentation engine entirely in the browser without any network requests. The engine tokenizes text into sentences using a finite-state machine that recognizes sentence boundaries by identifying punctuation marks (. ! ?) followed by whitespace or end-of-string. The engine also handles common edge cases such as abbreviations (e.g., "Mr.", "Dr.", "etc.") by maintaining a list of common abbreviations that should not terminate sentences. Once sentences are segmented, the engine counts words by splitting on whitespace and filtering out empty strings. The tool processes text in batches to avoid blocking the main thread, and it preserves the original DOM structure by replacing text nodes with document fragments containing highlighted spans. The threshold is stored per domain, allowing different thresholds for different types of content. This approach ensures accurate, fast, and fully private sentence analysis without sending any data off-device.

THE PANEL

The floating panel is fully draggable and remembers its position per site, snapping to the edges of the viewport when dragged near them. You can collapse the panel to a small icon to minimize screen distraction and expand it back with a single click. The panel is resizable from the bottom-right corner, giving you more space to view statistics and controls. Press the Escape key to close the panel instantly. The panel remains open across page navigation within the same domain, maintaining your current toggle states and threshold setting. All preferences—panel position, highlight toggle state, and word threshold—are saved per domain for a seamless experience.

PLEASE NOTE

Long Sentence Highlighter requires the free BotGentz extension to be installed and enabled, as it relies on the cross-extension messaging API provided by BotGentz for DOM access permissions. Because websites frequently update their structure, scanning and highlighting may require periodic script updates to maintain compatibility. If the tool does not highlight text as expected, please check for updates or report the issue. All text processing occurs entirely in your browser. No page content, text samples, or analysis results are ever sent to any server. The extension does not read, store, or transmit any personal information. It only reads the DOM of the pages you choose to interact with and applies visual highlights at your request.