Quick Unit Converter on Selection

WHAT IT DOES

Quick Unit Converter on Selection detects numeric values with units in any text you select and instantly shows the converted value in a tooltip. Simply highlight text like "10 cm", "5 kg", or "100°F" and a small tooltip appears with the conversion (e.g., "10 cm → 3.94 in"). The extension supports six unit categories: length (cm, m, km, in, ft, yd, mi), weight (g, kg, lb, oz), temperature (°C, °F, K), volume (ml, L, gal, fl oz), speed (km/h, mph, m/s), and area (m², ft², acre). A detailed panel shows all available conversions for the detected unit, and you can copy the converted value to your clipboard with one click. The tooltip updates in real-time as you change your selection, making it perfect for quick reference while reading, researching, or working with measurements.

WHERE IT RUNS

The extension works on every website with selectable text, including news sites, technical documentation, e-commerce pages, academic articles, and any other page containing measurements. It runs locally in your browser, analyzing selected text and performing conversions without sending any data to external servers. The extension supports all major browsers and adapts to both desktop and mobile viewports seamlessly.

HOW TO USE

After installation, simply select any text containing a number and a unit (e.g., "2.54 cm", "100 kg", "72°F"). A tooltip appears near your cursor showing the converted value in the most common alternative unit. To see all available conversions, open the extension panel and click "Show Conversions," or click the badge (if enabled). The panel displays every conversion for the detected unit. From the panel, click "Copy" to copy the conversion result to your clipboard. To customize the experience, open the extension panel and choose the tooltip position (Above cursor, Below cursor, or Beside cursor). Toggle "Show all conversions in tooltip" to show multiple conversions at once. Choose your preferred unit system (Metric, Imperial, or Both). For per-site customization, enable or disable the extension on specific websites using the per-site controls.

THE ACTUAL MECHANISM — UNIT DETECTION REGEX WITH CATEGORY-BASED CONVERSION ENGINE

The extension uses a multi-stage detection and conversion pipeline. First, it applies category-specific regex patterns to the selected text. Each category has a pattern that matches a number followed by a unit identifier (e.g., `(\d+\.?\d*)\s*(cm|m|km|...)`). When a match is found, the extension extracts the numeric value and the unit string. The unit is normalized (e.g., "km/h" → "kmh") and validated against the unit definitions for that category. Each unit has a `toBase` function that converts the value to a base unit (e.g., meters for length, kilograms for weight, Celsius for temperature) and a `fromBase` function that converts from the base unit to the target unit. For temperature, special handling is applied because the conversion is not linear (offset). The extension then generates a list of all conversions from the detected unit to every other unit in the same category. The tooltip shows the primary conversion (most common alternative) and optionally additional conversions. The panel displays all conversions in a sortable list. All calculations are performed client-side with no external API calls.

THE PANEL

The settings panel is a lightweight, draggable overlay that appears in the center of your screen. You can reposition it by clicking and dragging the title bar; release it near the screen edge and it will snap into place automatically. To collapse the panel into a compact title bar, click the minimize button, expanding it again with the same control. The panel is fully responsive, adapting to different screen resolutions with a minimum width of 300px and a maximum of 480px. Press the Escape key at any time to dismiss the panel without applying changes. All controls—the enable/disable toggle, show conversions button, close button, position selector, all conversions toggle, unit system selector, and per-site controls—are accessible within a clean, high-contrast interface that respects your system's color scheme.

PLEASE NOTE

This extension requires the free BotGentz companion extension to be installed and active, which provides the underlying DOM access, clipboard, and storage engine. The unit detection uses regex patterns that match common unit notations—unusual formats or abbreviations may not be detected. The tooltip may not display correctly on very small selections or when the selection is near the edge of the viewport. Temperature conversions use the standard formulas (°F = °C × 9/5 + 32, K = °C + 273.15). All conversions are approximate and rounded to reasonable precision. No personal data, browsing history, or selected text is ever collected, stored, or transmitted. All settings are saved using the browser's storage API and remain solely on your device. The extension does not inject ads, trackers, or analytics of any kind.