Sizzy Does Not Simulate Browser Engines

Sizzy only simulates viewport size and user agent—it doesn't simulate different browser engines.

For example, setting the user agent to Firefox while creating a custom device or modifying an existing device still renders the page using the Chromium engine, instead of Firefox's Gecko.

Therefore, there might be minor differences between how the website looks in Sizzy vs how it looks in a "real" Firefox browser.