Decorative line thickness
text-decoration-thickness

Set the thickness of underlines, overlines, strikethroughs, and wavy lines.
Property values
Use the keyword from-font
to specify that the thickness should be determined by the font file.
Alternatively, specify the thickness using a value with units such as px
or em
.
Examples
/* use the type foundry's specification */
text-decoration-thickness: from-font;
/* override the type foundry's specification */
text-decoration-thickness: 2px;