em unit

The em CSS length unit is a font-relative length equal to the specified font size. In an element with a 2 inch font, 1em equals 2 inches.

Baseline Status: Achieved Widely Available on Jan 29, 2018 (Cross-browser Newly Available since Jul 29, 2015).

Desktop Browser Engine Support

Google Chrome

1

Supported

Mozilla Firefox

1

Supported

Apple Safari

1

Supported

Microsoft Edge

12

Supported

Mobile Browser Engine Support

Chrome Android

18

Firefox Android

4

Safari iOS

1

Specifications and References

MDN Browser Compat Data Keys: