WOFF Fonts Knowledge Base

Introduction to WOFF font

Web Open Font Format (WOFF), is a font file format designed for use specifically on the web. It was developed to overcome some of the limitations and challenges of traditional font formats, such as TrueType and OpenType, in web development.

WOFF format provides you with:

To use WOFF fonts in web development, you typically include them in your project’s HTML and CSS files using the @font-face rule.

Advantages and disadvantages of WOFF font

The table below shows the pros and cons of WOFF fonts, so you could decide whether to use it in your project or not.

WOFF fonts are compressed, making them smaller in file size compared to some other font formats. This results in faster loading times for web pages.Older browsers may not fully support this format. This can be a concern if you need to support legacy systems.
Widely supported by major web browsers, which gives consistent font rendering across different platforms and browsers.Some high-quality commercial fonts may require purchasing licenses to use them on the web with WOFF format.
WOFF fonts allow font creators to embed licensing and copyright information within the font file itself.WOFF fonts may render differently on different devices or browsers due to varying font rendering engines.
Support advanced typographic features, such as ligatures, kerning, and stylistic alternates.Proper font optimization techniques are essential to keep file sizes in check.
Can improve web accessibility by providing better control over font rendering, spacing, and line heights.
WOFF fonts can be hosted on the same domain as the web page, reducing the risk of security vulnerabilities associated with cross-origin requests for fonts.

Technical details of WOFF fonts

Web Open Font Format is designed specifically for web usage. Here are some key technical details about it:

  1. WOFF fonts use compression techniques to reduce file size compared to the raw TrueType or OpenType font files.
  2. They include metadata that provides information about the font, including its name, copyright, and licensing details. It can be accessed programmatically, making font licensing compliance simpler.
  3. WOFF fonts contain the font data needed for rendering text, including glyph shapes, metrics, and other font-related information. This data is encoded in a format that web browsers can interpret.
  4. May include hinting information that is used to improve the legibility of fonts at small sizes by adjusting the position of individual glyphs and controlling anti-aliasing.
  5. They can be subsetted, which means that only a portion of the font’s glyphs is included in the file.
  6. WOFF fonts are typically served with a font/woff or font/woff2 MIME type when requested from a web server. The MIME type helps browsers understand how to handle the font file.
  7. Using WOFF fonts on a web page, web developers often define a fallback font stack in CSS to make sure that if the specified WOFF font is not available or fails to load, the browser uses a default system or another specified one.
  8. If WOFF fonts are hosted on a different domain than the web page, CORS headers must be set on the font server to allow web browsers to access the font files securely. This helps prevent cross-site request forgery (CSRF) attacks.
  9. In addition to the original WOFF format, there is a newer format called WOFF2 that offers even better compression and smaller file sizes than WOFF, but it may not be supported by all older browsers.
  10. WOFF fonts can include a wide range of Unicode characters, so they can display text in multiple languages and scripts.

How do WOFF fonts render glyphs?

Web Open Font Format fonts render glyphs in a manner similar to other font formats. When a web browser or rendering engine encounters text content on a web page that requires a specific font, it follows these steps to render the glyphs:

  1. When a web page is loaded, and it specifies the use of a particular font via CSS (e.g., font-family), the browser checks if it has the required font in its cache. If not, it initiates a request to the web server hosting the font file.
  2. If the font is absent, the browser sends a request to the server for the WOFF font file associated with the specified font family.
  3. After receiving the font file, the browser parses the WOFF font data, extracting information about glyph shapes, metrics, character mapping (Unicode mapping), etc.
  4. When text is rendered on the web page, the browser maps each character in the text to the corresponding glyph in the font based on Unicode or encoding information.
  5. The browser uses the glyph information to render the individual characters on the web page. This includes determining the size, position, and spacing of each glyph relative to other glyphs in the text.
  6. To improve the visual quality of text and smooth the edges of characters, the browser may apply anti-aliasing techniques to the glyph shapes.
  7. If there is kerning and ligature information, the browser may adjust the spacing between characters and replace specific character combinations with ligatures.
  8. If the font is not available or fails to load, the browser uses a default system font or another one specified in the CSS font stack.
  9. Finally, the browser displays the rendered text on the web page, using the glyphs generated from the WOFF font.


CompressionUses a compression method based on zlib compressionUses a more advanced and efficient compression algorithm called Brotli. This compression is highly efficient and often results in font files that are around 30-50% smaller than their WOFF equivalents.
Browser supportHas good support in modern web browsers older browsers might have limited or no support for this format.Has broader support among modern browsers.
File sizeAre compressed and smaller than raw font formats, but their file sizes can still be relatively large.They are typically much smaller than both WOFF and the original raw font formats.
PerformanceOffer better performance compared to raw font formats due to their reduced file size and optimized delivery.Provide superior web performance by significantly reducing the time it takes to download font files.

How to create a WOFF font?

Creating a Web Open Font Format (WOFF) font involves conversion of other font formats into the WOFF format. Here are the steps of the process:

  1. Get a TTF or OTF font. You can either create your own font using font design software or use an existing font that you have the appropriate licensing rights for.
  2. Ensure that your font file is well-designed and free from errors.
  3. Convert to WOFF.
  4. Before using the WOFF font on your website, test the font and solve issues if found any.
  5. Host the WOFF font file on your web server or a content delivery network (CDN) so that it can be accessed by your website. Make sure to set the appropriate MIME type for WOFF files, which is typically font/woff.
  6. Use the WOFF Font in CSS with the @font-face rule that defines the WOFF font and specify its source using the src property. Here’s an example:
1    @font-face { 
2        font-family: 'YourFontName'; 
3        src: url('path/to/your-font.woff') format('woff'); 
4    }
  1. Apply the font to specific HTML elements using the font-family property in your CSS.
1    body { 
2        font-family: 'YourFontName', sans-serif; 
3    }
  1. Make sure that you have the appropriate licensing rights for the font you’re using on your website, especially if it’s a commercial font.

How to optimize WOFF files?

Optimizing WOFF (Web Open Font Format) fonts is essential for improving web performance by reducing the font file size while maintaining high-quality typography. Here are the ways you can do it:

  1. Subsetting the font ensures you only include the characters needed for your website. This will not only reduce the file size but will help you manage it easier.
  2. Find out whether you really need hinting and kerning information in your font as this increases the file size. Some fonts may work well without hinting and kerning, especially at larger sizes.
  3. Optimize Glyphs by reviewing their outlines and removing any unnecessary points or curves while maintaining visual quality. Font editing software can help with this optimization.
  4. Compress your WOFF font files using tools like gzip or Brotli on your web server to reduce file size when serving fonts to the browser.
  5. Implement proper caching headers on your web server to ensure that fonts are cached by the browser and prevent unnecessary re-downloading of fonts on subsequent visits to your website.
  6. Use a content delivery network (CDN) that often has optimized caching and delivery mechanisms that can improve font loading times.
  7. Try using the preload attribute in your HTML to load critical fonts early in the page-loading process to reduce font-related render-blocking delays.
  8. Use the font-display CSS property to control how fonts are displayed when loading.
  9. Use responsive typography techniques to load different font variants based on screen size and resolution. Have media queries to load different font files for different devices and screen sizes.
  10. Have the number of fonts you use on your site limited because each additional font adds to the overall file size.
  11. Avoid applying excessive font customizations (e.g., multiple font weights and styles) if they are not essential for your design.
  12. Regularly test your website’s performance using tools like Google PageSpeed Insights or GTmetrix to identify font-related performance issues.

W3C (World Wide Web Consortium) standards and specifications in relation to WOFF fonts.

The W3C is responsible for developing and maintaining various standards and specifications related to web technologies, including fonts. One important standard related to fonts on the web is the Web Open Font Format (WOFF). WOFF is a font format that is specifically designed for use on the web, and it provides a way to package fonts for efficient delivery and use on web pages. Here are some key W3C points:

WOFF 1.0 (Web Open Font Format 1.0):

WOFF 2.0 (Web Open Font Format 2.0):

WOFF File Format (Working Draft):

Web Fonts Working Group:

CSS Fonts Module Level 3:


Development and use of Web Open Font Format (WOFF) fonts have significantly improved the web typography process. This versatile font format has empowered web designers and developers to bring more creative and accessible typographic experiences to users across the internet.

WOFF offers a range of benefits, including efficient compression for faster page loading times, improved cross-browser compatibility, and the ability to include custom typefaces without losing website performance. They have become an integral part of web design and are still very popular and supported.

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