Which is smaller: OTF or WOFF?

WOFF is typically 40-60% smaller than OTF due to gzip compression. A 200KB OTF becomes ~80-120KB WOFF.

Should I use WOFF or WOFF2 instead of OTF for web?

Use WOFF2 (smallest), with WOFF fallback for IE11. Never serve OTF directly for web - it's 3-5x larger.

Does WOFF maintain OTF's typography features?

Yes, WOFF is just compressed OTF/TTF. All OpenType features (ligatures, kerning, stylistic sets) are preserved.

When should I use OTF vs WOFF?

Use OTF for desktop/print design work. Use WOFF (and WOFF2) exclusively for web deployment.

Can design software open WOFF files?

Most design software (Adobe, Figma, Sketch) cannot open WOFF directly. Keep OTF/TTF as source, export WOFF for web.

OTF vs WOFF: Complete Format Comparison

Comprehensive comparison of OpenType Font (OTF) and Web Open Font Format (WOFF) covering technical differences, use cases, performance, and when to use each format

TL;DR

In Simple Terms

OTF is desktop format (~168 KB), WOFF is web format (~90 KB). Different purposes: OTF for installation, WOFF for web delivery via @font-face.Use OTF as source file for design work. Convert OTF to WOFF for web use—achieves 50% file size reduction without quality loss.Modern recommendation: Convert OTF to WOFF2 (primary, 68% smaller) + WOFF (fallback, 50% smaller) for optimal web performance and coverage.

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In this article

OpenType Font (OTF) and Web Open Font Format (WOFF) represent two complementary font technologies serving distinct purposes in modern typography. OTF, developed jointly by Adobe and Microsoft in 1996, is a desktop font format designed for installation on operating systems, supporting both TrueType and PostScript outline data with advanced typographic features. WOFF, created by Mozilla, Opera, and Microsoft in 2009 and standardized by W3C in 2012, is specifically designed for web use—it's essentially a compressed wrapper around OpenType/TrueType data optimized for website delivery with built-in metadata and licensing information.

The fundamental distinction is purpose-driven: OTF is for desktop applications (Word, Photoshop, InDesign), while WOFF is for web browsers. OTF files are uncompressed, typically 150-300 KB, allowing operating systems to access font tables directly. WOFF files contain the same font data compressed with zlib, reducing size by 40-50% to 80-150 KB for faster web delivery. Both formats contain identical glyph outlines, kerning, and OpenType features—WOFF simply adds compression, metadata fields, and a web-optimized structure. This makes OTF the source format for design and desktop work, while WOFF is the distribution format for websites.

This comprehensive guide compares OTF and WOFF across all relevant dimensions to clarify their relationship and optimal usage. You'll learn the technical specifications of each format, how WOFF wraps and compresses OTF data, appropriate use cases showing OTF for desktop and WOFF for web, browser compatibility demonstrating WOFF's universal support, performance comparisons quantifying compression benefits, conversion workflows from OTF to WOFF, and why WOFF2 (the successor to WOFF) offers even better compression. Whether planning font deployment strategies or optimizing web performance, this guide provides essential knowledge for leveraging both formats effectively.

Format Overview

OpenType Font (OTF)

History and Purpose:

• Developed by Adobe and Microsoft (1996) to unify TrueType and PostScript
• Designed as universal desktop font format
• Supports advanced typography (ligatures, alternates, small caps)
• Works across Windows, macOS, Linux
• Industry standard for professional typography

Technical Characteristics:

• Can contain TrueType outlines (quadratic curves)
• Or PostScript/CFF outlines (cubic curves)
• Comprehensive OpenType features (GSUB, GPOS tables)
• Uncompressed for direct OS access
• Extensions: .otf (PostScript outlines) or .ttf (TrueType outlines)

Typical Use:

• Installing fonts on desktop computers
• Using in design applications (Photoshop, InDesign, Illustrator)
• Document creation (Word, PowerPoint, PDF)
• Source format for web font conversion

Web Open Font Format (WOFF)

History and Purpose:

• Created by Mozilla, Opera, Microsoft (2009)
• W3C Recommendation (2012)
• Designed specifically for web font delivery
• Addresses bandwidth and licensing concerns
• Universal browser support since 2012

Technical Characteristics:

• Compressed wrapper around OpenType/TrueType data
• Uses zlib compression (same as gzip)
• Contains identical glyph data to source OTF/TTF
• Includes metadata block for licensing/vendor info
• Extension: .woff

Typical Use:

• Embedding fonts in websites via @font-face
• Web application typography
• Email templates (with fallbacks)
• Any browser-based content

Key Relationship: WOFF Contains OTF Data

Critical understanding: WOFF is not a different font format—it's a compression and packaging system for OpenType/TrueType fonts.

• Same glyph outlines: Identical curves, same visual appearance
• Same features: All OpenType features preserved
• Same metrics: Identical spacing, kerning, line height
• Only difference: WOFF adds compression + web-specific metadata

Converting OTF to WOFF is lossless—the font data is identical, just compressed for web delivery.

Technical Differences

Side-by-Side Technical Comparison

Aspect	OTF	WOFF
Primary Purpose	Desktop OS installation	Web font delivery
Compression	None (uncompressed)	zlib (40-50% smaller)
File Size	150-300 KB	80-150 KB
Font Data	Direct OpenType tables	Same tables, compressed
Metadata	Standard font metadata	+ Web metadata block
Browser Support	Limited (not optimal)	99%+ (recommended)
OS Installation	Yes (native)	No (web only)
Loading Speed	Baseline	40-50% faster
Best For	Desktop apps, design	Websites, web apps

How WOFF Compresses OTF Data

Compression Process:

Extract OpenType tables from OTF file
Compress each table individually with zlib
Add WOFF header and table directory
Optionally add metadata block (vendor, license info)
Result: 40-50% smaller file with identical font data

Decompression (Browser):

Browser downloads WOFF file
Decompresses tables back to OpenType format
Uses standard OpenType rendering pipeline
Result: Identical rendering to original OTF

WOFF Metadata Block

WOFF includes optional metadata not present in OTF:

• Vendor information: Foundry name, contact details
• License details: Usage restrictions, terms
• Copyright: Rights holder information
• Description: Font purpose, history
• Trademark: Trademark notices

This metadata helps foundries protect fonts while enabling web distribution.

File Size Comparison Example

Roboto Regular font (Latin character set):

Format	Size	Reduction
OTF/TTF	168 KB	Baseline
WOFF	90 KB	46% smaller
WOFF2	53 KB	68% smaller

Desktop vs Web Use Cases

When to Use OTF

Perfect For:

• Desktop installation: Installing fonts on Windows, macOS, Linux
• Design applications: Photoshop, Illustrator, InDesign, Figma
• Office documents: Word, PowerPoint, Excel, PDF creation
• Font development: Creating and editing fonts
• Source files: Master format before web conversion
• Print production: Professional typesetting and layout

Rule: Use OTF for any desktop or design application where fonts are installed locally.

When to Use WOFF

Perfect For:

• Website typography: All website @font-face implementations
• Web applications: Browser-based apps and tools
• Email templates: HTML emails with custom fonts (with fallbacks)
• Progressive web apps: PWAs needing offline font access
• Mobile web: Responsive sites on phones/tablets

Rule: Use WOFF (or better, WOFF2) for all web font delivery.

Note: WOFF2 is now preferred over WOFF for even better compression (68% vs 46% reduction).

Common Workflow Pattern

Design phase: Install OTF/TTF on designer's computer for use in Photoshop, Figma, etc.
Development phase: Convert OTF to WOFF2 and WOFF for web use
Implementation: Use WOFF2/WOFF in website @font-face declarations
Documentation: Keep source OTF files for future conversions

This pattern maintains quality while optimizing performance.

Browser and Platform Compatibility

Browser Support Matrix

Browser	OTF/TTF	WOFF	Notes
Chrome	✓	✓	Both supported, WOFF preferred
Safari	✓	✓	Both supported, WOFF preferred
Firefox	✓	✓	Both supported, WOFF preferred
Edge	✓	✓	Both supported, WOFF preferred
IE 9-11	~	✓	WOFF better support

Coverage: WOFF supported by 99%+ browsers. OTF works but not optimized for web.

Why WOFF for Web

Smaller file size: 40-50% reduction means faster page loads
Better caching: Browsers cache WOFF more effectively
Licensing metadata: WOFF supports embedded licensing info
Web standard: W3C recommended specifically for web use
Universal support: Works in all modern browsers
Performance optimization: Designed for HTTP delivery

Recommended Web Font Stack (2025)

@font-face {
  font-family: 'MyFont';
  src: url('/fonts/font.woff2') format('woff2'),
       url('/fonts/font.woff') format('woff');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

/* WOFF2 (primary): 97%+ browsers, best compression */
/* WOFF (fallback): 99%+ browsers, good compression */
/* No OTF/TTF needed for web (not optimized) */

Performance Comparison

Load Time Comparison (4G Connection)

Format	File Size	Load Time	Bandwidth
OTF/TTF	168 KB	~1.1s	168 KB
WOFF	90 KB	~0.6s (45% faster)	90 KB (46% less)
WOFF2	53 KB	~0.35s (68% faster)	53 KB (68% less)

Real-World Impact

Example: E-commerce Site with 4 Font Files

Using OTF:

• 4 fonts × 168 KB = 672 KB
• Load time: ~4.5s on 4G
• Poor FCP, affects LCP

Using WOFF2:

• 4 fonts × 53 KB = 212 KB
• Load time: ~1.4s on 4G
• 460 KB saved, 3.1s faster

Core Web Vitals Impact

Using WOFF/WOFF2 instead of OTF improves:

• FCP (First Contentful Paint): Faster font load = faster text rendering
• LCP (Largest Contentful Paint): If text is largest element, smaller fonts = better LCP
• PageSpeed score: Typically 10-30 point improvement
• Mobile experience: Critical for 3G/4G connections

Conversion and Workflow

Converting OTF to WOFF/WOFF2

Method 1: Using FontTools (Recommended)

# Install FontTools
pip install fonttools brotli

# Convert to WOFF2 (best compression)
fonttools ttLib.woff2 compress font.otf
# Creates font.woff2

# Convert to WOFF (fallback)
fonttools ttLib.woff compress font.otf
# Creates font.woff

Method 2: Online Converter

Visit font-converters.com
Upload OTF file
Select WOFF2 and WOFF as output formats
Click Convert and download

Complete Workflow

Source: Obtain OTF/TTF font files (purchase or download free fonts)
Verify licensing: Ensure you have rights to use on web
Optional subsetting: If font is large, subset to needed characters
Convert: Generate WOFF2 (primary) and WOFF (fallback)
Upload: Place font files in /fonts/ directory on server
Implement CSS: Add @font-face declarations
Test: Verify fonts load in Chrome, Safari, Firefox
Optimize: Add font-display: swap, configure caching

Best Practices Checklist

☐ Keep original OTF files as source of truth
☐ Convert to WOFF2 for modern browsers (primary)
☐ Convert to WOFF for older browsers (fallback)
☐ Don't serve OTF directly to web (not optimized)
☐ Use font-display: swap to prevent FOIT
☐ Configure 1-year cache headers
☐ Consider subsetting for large fonts
☐ Preload critical fonts
☐ Test in multiple browsers
☐ Monitor with PageSpeed Insights

Summary: OTF vs WOFF

OTF and WOFF serve complementary purposes: OTF for desktop installation and design work, WOFF for web delivery. WOFF is not a different font format—it's a compressed wrapper around OpenType data, reducing file size by 40-50% while preserving identical glyphs, features, and metrics. Both formats contain the same font information; WOFF simply adds compression and web-specific metadata for efficient HTTP delivery.

Use OTF for desktop applications (Photoshop, Word, design tools) and as source files. Convert OTF to WOFF2 and WOFF for web deployment—this reduces file size from 168 KB to 53 KB (68% reduction with WOFF2), improving load times and Core Web Vitals. Never serve OTF directly to websites; always convert to web-optimized formats. WOFF2 is now preferred over WOFF for even better compression while maintaining universal browser support (97%+).

Written & Verified by

Sarah Mitchell

Product Designer, Font Specialist

OTF vs WOFF FAQs

Common questions answered about this font format comparison