Understanding Web Font Formats
Web fonts are fonts specifically optimized for use on websites. Unlike desktop fonts that prioritize visual richness and compatibility with design software, web fonts are designed to download quickly and render consistently across browsers.
The four main formats you'll encounter are TTF, OTF, WOFF, and WOFF2. Each has distinct characteristics that make it suitable for different use cases. Understanding these differences helps you choose the right format for your project.
Why Font Format Matters
Font file size directly impacts website performance. A single font file can range from 20KB to 500KB depending on the format and the number of characters it supports. For other web assets, tools like Compress.FAST can help reduce image and document sizes to complement your font optimization strategy.
Font Loading and Core Web Vitals
- LCP Impact — Large font files delay Largest Contentful Paint. WOFF2 files are typically 30-50% smaller than TTF.
- CLS Risk — Using system fonts eliminates layout shift, but custom fonts can cause shifts if not loaded properly.
- FOIT — Flash of Invisible Text occurs when browsers wait for fonts to load before displaying text.
Modern web development practices recommend using WOFF2 with a preconnect hint, and optionally loading fonts asynchronously to prevent blocking page render.
Format-by-Format Breakdown
TTF (TrueType Font)
TrueType Font (TTF) was developed by Apple and Microsoft in the late 1980s as a scalable font format for both screen and print. It became the foundation for desktop typography and remains widely supported today.
| Characteristic | TTF |
|---|---|
| Compression | None (raw) |
| File Size | Large (50-200KB typical) |
| Browser Support | Universal (all browsers) |
| Best For | Desktop applications, legacy support |
OTF (OpenType Font)
OpenType Font (OTF) is a successor to TrueType, developed jointly by Adobe and Microsoft. It supports advanced typography features like ligatures, small caps, and alternate characters that designers often need.
| Characteristic | OTF |
|---|---|
| Compression | None (raw), sometimes CFF outline |
| File Size | Medium (40-150KB typical) |
| Browser Support | Universal (all browsers) |
| Best For | Professional typography, design software |
WOFF (Web Open Font Format)
WOFF is a web-optimized format that wraps TTF or OTF fonts with compression. It was designed specifically for web use and became a W3C Recommendation on December 13, 2012.
| Characteristic | WOFF |
|---|---|
| Compression | zlib (40-50% smaller) |
| File Size | Small (30-80KB typical) |
| Browser Support | IE9+, Chrome 5+, Firefox 3.6+, Safari 5.1+ |
| Best For | Legacy browser fallback |
WOFF2 (Web Open Font Format 2)
WOFF2 is the successor to WOFF, using the Brotli compression algorithm for 25-30% better compression than WOFF. It became a W3C Recommendation on March 1, 2018 and is now the recommended format for modern web development.
| Characteristic | WOFF2 |
|---|---|
| Compression | Brotli (25-30% smaller than WOFF, 60-70% smaller than TTF) |
| File Size | Smallest (20-50KB typical) |
| Browser Support | Chrome 36+, Firefox 39+, Safari 12+ (desktop) / 10+ (iOS), Edge 14+ |
| Best For | Modern websites (recommended) |
Variable Fonts
Browser Support Comparison
Understanding browser support is essential for making the right format choice. Here's a comprehensive breakdown of format support across browsers.
| Browser | TTF | OTF | WOFF | WOFF2 |
|---|---|---|---|---|
| Chrome | Yes | Yes | Yes | Yes (v36+) |
| Firefox | Yes | Yes | Yes (v3.6+) | Yes (v39+) |
| Safari | Yes | Yes | Yes (v5.1+) | Yes (v12+ desktop, v10+ iOS) |
| Edge | Yes | Yes | Yes | Yes |
| IE | Yes | Limited | Yes (v9+) | No |
Coverage Statistics
As of 2026, WOFF2 alone covers approximately 96.83% of global browser users. Adding WOFF as a fallback increases coverage to over 99%.
File Size Comparison
The primary advantage of web-optimized formats is reduced file size. Here's a comparison of typical file sizes for the same font in different formats.
| Format | Typical Size | vs TTF |
|---|---|---|
| TTF (TrueType) | 150-300 KB | — (baseline) |
| OTF (OpenType) | 150-300 KB | ~0-20% smaller |
| WOFF | 60-175 KB | 40-50% smaller |
| WOFF2 | 15-100 KB | 60-70% smaller |
Real-world examples: Roboto Regular is 168 KB as TTF, 53 KB as WOFF2 (68% smaller). Open Sans is 215 KB as TTF, 68 KB as WOFF2. With Latin-only subsetting, WOFF2 files can be just 10-25 KB.
Using WOFF2 instead of TTF can reduce font transfer size by 65-70%. For a page that loads 3 font files (regular, bold, italic), this represents a savings of 150-200KB—significant for mobile performance.
When to Use Each Format
Here's a practical decision guide to help you choose the right format for your specific use case.
For Modern Websites
Use WOFF2 as your primary format WOFF2 offers the best compression and supports 96%+ of browsers. It's the recommended format for all new web projects. Add WOFF as a fallback Include a WOFF file for browsers that don't support WOFF2. This catches the remaining 3-4% of users (mostly older mobile browsers). Use system font stacks as final fallback Specify system fonts in your CSS font-family as the last option. This ensures text is always visible.
For Desktop Applications
Desktop applications have different requirements than websites. They need to work offline and integrate with design software.
- TTF — Best for maximum compatibility with older software and operating systems.
- OTF — Best for professional design applications that need advanced typography features.
Avoid WOFF/woff2 for Desktop
Web-optimized formats are not recommended for desktop applications. They add unnecessary complexity and aren't necessary for applications that download once and run locally.
For Email Clients
Email clients have limited font support. Most don't support web fonts at all, and those that do have inconsistent behavior.
Email Font Strategy
For email, stick to web-safe fonts (Arial, Georgia, Times New Roman) in your CSS. If you must use custom fonts, ensure your design degrades gracefully to system fonts.
How to Convert Between Formats
Converting between font formats is straightforward with the right tools. Here's how to convert your fonts for different use cases.
Converting Desktop Fonts to Web Fonts
If you have TTF or OTF fonts and need web-optimized versions, converting to WOFF2 is the standard approach:
Converting Web Fonts to Desktop Fonts
Sometimes you need to go the other direction—converting web fonts back to desktop formats for use in design software or other applications:
TTC Files
- What is TTC? — TTC (TrueType Collection) is a container that holds multiple font families in a single file, like Noto Sans.
- Converting TTC — You'll need to extract individual fonts first. Convert TTC to TTF extracts each font as a separate file.
Frequently Asked Questions
Here are answers to common questions about web font formats.
Does WOFF2 work in all browsers?
WOFF2 works in all modern browsers: Chrome 36+, Firefox 39+, Safari 12+ (desktop)/10+ (iOS), and Edge 14+. It does not work in Internet Explorer. However, WOFF2 covers approximately 96.83% of global browser users.
For the remaining users, you should include a WOFF fallback. This brings coverage to over 99% of browsers.
Can I use TTF fonts directly on my website?
Yes, you can use TTF fonts directly on websites, but it's not recommended. TTF files are uncompressed and significantly larger than web-optimized formats.
A typical TTF file is 50-100KB, while the same font as WOFF2 might be only 20-40KB. Using WOFF2 reduces bandwidth usage and improves page load times, especially on mobile devices.
What's the smallest web font format?
WOFF2 is the smallest web font format available. It uses Brotli compression, which is approximately 30% more efficient than the zlib compression used in WOFF.
For a typical font, WOFF2 files are 50-70% smaller than the equivalent TTF file. This makes WOFF2 the format of choice for performance-conscious web developers.
Do I need both WOFF and WOFF2?
For most modern websites, WOFF2 alone is sufficient—it covers 96.83%+ of users. However, adding WOFF as a fallback catches the small number of users on browsers that don't support WOFF2 (mostly older Safari on iOS and some Android browsers).
The typical CSS approach is to include both formats, listing WOFF2 first (for browsers that support it) and WOFF second (as fallback):
@font-face {
font-family: 'MyFont';
src: url('myfont.woff2') format('woff2'),
url('myfont.woff') format('woff');
}How do I convert my font to WOFF2?
You can convert fonts to WOFF2 using online converters or command-line tools. Online converters like Convert.FAST let you upload your TTF or OTF file and download the WOFF2 version instantly.
For batch conversions or automated workflows, tools like fonttools (Python) or Transfonter (web-based) are popular choices.