Is Everything Metric (Auto Unit Converter) safe?

Automatically adds metric conversions next to U.S. units on webpages.

This extension scans page text and inserts SI/metric equivalents in brackets for units such as feet, miles, pounds, gallons, mph, mpg, Fahrenheit, area, and volume. A toolbar button can turn conversion on or off globally, and Alt+M can force conversion when needed. It uses storage to save settings and needs access to webpages so it can modify visible text.