window: queryLocalFonts() method

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The window.queryLocalFonts() method returns a Promise that fulfills with an array of FontData objects representing the font faces available locally.

To use this method, the user must grant permission to access 'local-fonts' (permission status can be queried via the Permissions API). In addition, this feature may be blocked by a Permissions Policy set on your server.

Syntax

js

queryLocalFonts(options)

Parameters

options Optional

Contains optional configuration parameters. Currently only one property is defined:

postscriptNames

An array of font PostScript names. If this is specified, only fonts with PostScript names matching those in the array will be included in the results.

Return value

A Promise that fulfills with an array of FontData objects representing the font faces available locally.

Exceptions

NotAllowedError DOMException

The user chose to deny permission to use this feature when presented with the browser's permission prompt after the method was first invoked.

SecurityError DOMException

Use of this feature was blocked by a Permissions Policy, or it was not called via a user interaction such as a button press.

Examples

For a working live demo, see Font Select Demo.

Font enumeration

The following snippet will query for all available fonts and log metadata. This could be used, for example, to populate a font picker control.

js

async function logFontData() {
  try {
    const availableFonts = await window.queryLocalFonts();
    for (const fontData of availableFonts) {
      console.log(fontData.postscriptName);
      console.log(fontData.fullName);
      console.log(fontData.family);
      console.log(fontData.style);
    }
  } catch (err) {
    console.error(err.name, err.message);
  }
}

Limiting returned results

To limit the returned font data to only a specific list of font faces, use the postscriptNames option.

js

async function returnSpecificFonts() {
  const availableFonts = await window.queryLocalFonts({
    postscriptNames: ["Verdana", "Verdana-Bold", "Verdana-Italic"],
  });

  return availableFonts;
}

Accessing low-level data

The blob() method provides access to low-level SFNT data — this is a font file format that can contain other font formats, such as PostScript, TrueType, OpenType, or Web Open Font Format (WOFF).

js

async function computeOutlineFormat() {
  try {
    const availableFonts = await window.queryLocalFonts({
      postscriptNames: ["ComicSansMS"],
    });
    for (const fontData of availableFonts) {
      // `blob()` returns a Blob containing valid and complete
      // SFNT-wrapped font data.
      const sfnt = await fontData.blob();
      // Slice out only the bytes we need: the first 4 bytes are the SFNT
      // version info.
      // Spec: https://docs.microsoft.com/en-us/typography/opentype/spec/otff#organization-of-an-opentype-font
      const sfntVersion = await sfnt.slice(0, 4).text();

      let outlineFormat = "UNKNOWN";
      switch (sfntVersion) {
        case "\x00\x01\x00\x00":
        case "true":
        case "typ1":
          outlineFormat = "truetype";
          break;
        case "OTTO":
          outlineFormat = "cff";
          break;
      }
      console.log("Outline format:", outlineFormat);
    }
  } catch (err) {
    console.error(err.name, err.message);
  }
}

Specifications

Specification
Local Font Access
# dom-window-querylocalfonts

Browser compatibility

BCD tables only load in the browser

See also