Very long texts consume browser memory and CPU for live counting and frequency analysis, so pasting manuscripts over ~500,000 characters (roughly 80,000–100,000 words) can cause Chrome or Firefox to spike CPU or Safari on macOS/iOS to crash. To avoid this, split the document into chapters and upload or paste each part separately, or turn off Analyze Frequency which stops the heavy top-50 computation. On desktop Chrome, increasing available memory and closing other tabs helps; on mobile use smaller chunks under 50 KB to keep the UI responsive.