Font Converter

Base64 Font Encoder

Convert font files to Base64 for embedding in CSS

Browser-BasedCSS GenerationBatch Processing

Drop your font files here

or click to browse from your computer

Supports: WOFF2, WOFF, TTF, OTF, EOT, SVG

Output Options

Developer & Verifier

Marcus Rodriguez

Developed by

Marcus Rodriguez

Lead Developer

Sarah Mitchell

Verified by

Sarah Mitchell

Product Designer, Font Specialist

What is Base64 Font Encoding?

Base64 font encoding converts binary font files into ASCII text strings embedded directly within CSS as data URIs, eliminating separate HTTP requests at the cost of a 33% file size increase and reduced compression efficiency. Base64 uses 4 ASCII characters to represent every 3 bytes of binary data — a mathematical constant that applies to every font format.

A CSS Wizardry study demonstrated the real-world impact: removing Base64-embedded fonts from CSS reduced compressed transfer size by 70%, from 232 KB to 68 KB Gzipped. Gzip compression efficiency drops from 90.4% to 74.9% when processing embedded Base64 content, because Base64 text has higher entropy than structured CSS.

Under HTTP/2, external font files with independent caching strategies outperform embedded fonts. Base64 forces font data onto the critical rendering path — all encoded assets download even if the page never uses those characters.

WOFF2 already uses Brotli compression, so Base64 re-encoding compressed data compounds inefficiency. The primary use case for Base64 fonts remains HTTP/1.1 environments with connection limits, or self-contained stylesheets for offline and email contexts where external resource loading is restricted.

Upload one or more font files in TTF, OTF, WOFF, or WOFF2 format. The encoder auto-detects the correct MIME type for each file and displays both the original file size and the Base64-encoded length for comparison. Each encoded font has its own copy button, and the tool generates complete @font-face CSS with data URIs ready to paste into your stylesheet. Batch download saves all encoded fonts as a single text file.

How to Use This Encoder

1

Upload Font File

Drag and drop or click to upload a TTF, OTF, WOFF, or WOFF2 font file for encoding.

2

Auto Encoding

The tool automatically detects the font format and generates the correct MIME type for the data URI.

3

Copy Output

Copy the complete data URI or full @font-face CSS rule with embedded Base64 font data.

4

Paste in Stylesheet

Add the generated CSS to your stylesheet to use the embedded font without external requests.

Features

TTF/OTF/WOFF/WOFF2 Support
Auto MIME Detection
CSS @font-face Output
Copy Data URI
File Size Comparison
Browser-Based Processing
No Upload to Server
Instant Conversion

Font MIME Types for Base64

FormatMIME TypeExtensionTypical Size Overhead
TrueTypefont/ttf.ttf~33%
OpenTypefont/otf.otf~33%
WOFFfont/woff.woff~33%
WOFF2font/woff2.woff2~33%

Frequently Asked Questions

What is Base64 encoding for fonts?
Base64 encoding converts binary font file data into a text string that can be embedded directly in CSS using a data URI. This eliminates the need for a separate font file request, embedding the font inline within your stylesheet.
When should I use inline Base64 fonts?
Use Base64 fonts for small icon fonts, single-page applications, email templates, or when you need a completely self-contained CSS file. Avoid it for large font files since Base64 adds ~33% size overhead.
What is the size overhead of Base64 encoding?
Base64 encoding increases file size by approximately 33%. A 20KB font becomes ~27KB when Base64 encoded. However, you save one HTTP request, which can offset the size increase for small fonts.
Which MIME type should I use for each font format?
TTF uses font/ttf, OTF uses font/otf, WOFF uses font/woff, and WOFF2 uses font/woff2. This tool auto-detects the correct MIME type based on your file extension.
Is Base64 encoding good for performance?
It depends. For small fonts (under 10KB), it can improve performance by eliminating an HTTP request. For larger fonts, the 33% size increase and blocking CSS parsing make external files with font-display: swap a better choice.
How do I use a Base64 data URI in CSS?
Place the data URI in the @font-face src property: src: url(data:font/woff2;base64,ABC123...) format("woff2"). This tool generates the complete @font-face CSS rule ready to copy.

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