FontFaceSet.check()

font

a font specification using the CSS value syntax, for example "italic bold 16px Roboto"

text

limit the font faces to those whose Unicode range contains at least one of the characters in text. This does not check for individual glyph coverage.

A Boolean value that is true if the font list is available.

The method returns true if the font list contains system or nonexistent fonts. This prevents websites from identifying users by the fonts they have installed.

In the following example, the first line will print true if the Courier font is available at 12px. The second line will print true if the font MyFont contains the "ß" character.

console.log(document.fonts.check("12px courier"));

console.log(document.fonts.check("12px MyFont", "ß"));

If the font given in the font specification does not exist, this function returns false:

console.log(document.fonts.check("12px NonExistingFont"));
// false