Font optimization in Astro

Introduction

Font optimization helps your website load faster and look better by using only the fonts you need.

When you want your website to load quickly on slow internet.

When you want to reduce the size of font files sent to the browser.

When you want to improve user experience by avoiding invisible or jumping text.

When you want to use custom fonts without slowing down your site.

When you want to improve your website's performance scores.

Syntax

Astro

import { font } from 'astro:font';

const myFont = font({
  src: './fonts/MyFont.woff2',
  preload: true,
  display: 'swap',
  subsets: ['latin'],
  weight: '400',
  style: 'normal'
});

preload: Loads the font early for faster display.

display: Controls how text is shown while font loads (e.g., 'swap' shows fallback text first).

Examples

This example loads the Roboto font with preload and swap display for better performance.

Astro

import { font } from 'astro:font';

const roboto = font({
  src: './fonts/Roboto-Regular.woff2',
  preload: true,
  display: 'swap'
});

This example loads Open Sans bold italic font with Latin and Cyrillic characters.

Astro

import { font } from 'astro:font';

const openSans = font({
  src: './fonts/OpenSans-Bold.woff2',
  weight: '700',
  style: 'italic',
  subsets: ['latin', 'cyrillic']
});

Sample Program

This Astro component imports and optimizes the Lato font. It preloads the font and uses the 'swap' display to show fallback text while loading. The font style is injected into the head, and the body uses the Lato font family.

Astro

---
import { font } from 'astro:font';

const lato = font({
  src: './fonts/Lato-Regular.woff2',
  preload: true,
  display: 'swap',
  subsets: ['latin'],
  weight: '400',
  style: 'normal'
});
---

<html lang="en">
  <head>
    <title>Font Optimization Example</title>
    <link rel="preload" href={lato.url} as="font" type="font/woff2" crossorigin />
    {lato.style}
  </head>
  <body style="font-family: 'Lato', sans-serif;">
    <h1>Hello, this text uses the optimized Lato font!</h1>
    <p>Font optimization helps this page load faster and look nice.</p>
  </body>
</html>

Important Notes

Always preload fonts you use above the fold to avoid invisible text.

Use font-display: swap to show fallback fonts while your custom font loads.

Limit font subsets and weights to only what you need to reduce file size.

Summary

Font optimization makes your website faster and smoother.

Astro's font helper lets you easily load and control fonts.

Preload fonts and use display: 'swap' for best user experience.

Practice

1. What is the main benefit of using font optimization in Astro projects?

easy

A. It makes the website load faster and improves user experience.

B. It changes the font color automatically.

C. It removes all fonts from the website.

D. It increases the file size of font files.

Solution

1. Step 1: Understand font optimization purpose

   Font optimization aims to improve website speed and smoothness by managing font loading efficiently.

2. Step 2: Identify the correct benefit

   Among the options, only making the website load faster and improving user experience matches the purpose.

3. Final Answer:

   It makes the website load faster and improves user experience. -> Option A

4. Quick Check:

   Font optimization = faster load and better UX [OK]

Hint: Font optimization improves speed and user experience [OK]

Common Mistakes:

• Thinking font optimization changes font colors
• Believing it removes fonts entirely
• Assuming it increases font file size

2. Which is the correct way to use Astro's Font helper to preload a font with display swap?

easy

A. Font.load('/fonts/myfont.woff2', { display: 'block' });

B. import { Font } from '@astrojs/font'; const myFont = Font({ src: '/fonts/myfont.woff2', display: 'swap', preload: true });

C. const myFont = Font('/fonts/myfont.woff2', { preload: false });

D. import Font from 'astro-font'; Font({ src: '/fonts/myfont.ttf' });

Solution

1. Step 1: Check correct import and usage

   Astro's Font helper is imported from '@astrojs/font' and called with an object including src, display, and preload keys.

2. Step 2: Verify options for preload and display

   import { Font } from '@astrojs/font'; const myFont = Font({ src: '/fonts/myfont.woff2', display: 'swap', preload: true }); correctly uses preload: true and display: 'swap' which matches best practices.

3. Final Answer:

   import { Font } from '@astrojs/font'; const myFont = Font({ src: '/fonts/myfont.woff2', display: 'swap', preload: true }); -> Option B

4. Quick Check:

   Correct import and preload with display swap = import { Font } from '@astrojs/font'; const myFont = Font({ src: '/fonts/myfont.woff2', display: 'swap', preload: true }); [OK]

Hint: Use import from '@astrojs/font' and set preload: true [OK]

Common Mistakes:

• Wrong import path or syntax
• Using display: 'block' instead of 'swap'
• Not setting preload to true

3. Given this Astro code snippet, what will be the effect on font loading?

import { Font } from '@astrojs/font';
const roboto = Font({ src: '/fonts/roboto.woff2', display: 'swap', preload: true });

export default function Page() {
  return <h1 style={{ fontFamily: roboto.style }}>Hello</h1>;
}

medium

A. The font will load but without any optimization or preload.

B. Roboto font is not preloaded and causes a flash of invisible text.

C. The font will not load because of a syntax error.

D. Roboto font is preloaded and swaps smoothly when loaded, improving page speed.

Solution

1. Step 1: Analyze the Font helper usage

   The font is imported with preload: true and display: 'swap', which preloads the font and allows fallback text until font loads.

2. Step 2: Understand the effect on rendering

   Using display: 'swap' avoids invisible text and preload speeds up font availability, improving page speed and user experience.

3. Final Answer:

   Roboto font is preloaded and swaps smoothly when loaded, improving page speed. -> Option D

4. Quick Check:

   Preload + display swap = smooth font load [OK]

Hint: Preload true + display swap = smooth font loading [OK]

Common Mistakes:

• Assuming no preload causes no flash
• Thinking syntax error exists here
• Ignoring display: 'swap' effect

4. Identify the error in this Astro font optimization code:

import { Font } from '@astrojs/font';
const openSans = Font({ src: '/fonts/opensans.woff2', display: 'fallback', preload: 'yes' });

medium

A. The preload option should be a boolean, not a string.

B. The display option 'fallback' is invalid in Astro.

C. The src path must end with .ttf, not .woff2.

D. Font helper must be called with a string, not an object.

Solution

1. Step 1: Check preload option type

   Preload expects a boolean (true or false), but 'yes' is a string, causing an error.

2. Step 2: Validate other options

   Display: 'fallback' is valid CSS font-display value, .woff2 is a valid font format, and Font helper accepts an object.

3. Final Answer:

   The preload option should be a boolean, not a string. -> Option A

4. Quick Check:

   Preload must be true/false, not 'yes' [OK]

Hint: Preload must be true or false, never a string [OK]

Common Mistakes:

• Using string 'yes' instead of boolean true
• Thinking .woff2 is invalid
• Assuming display: 'fallback' is wrong

5. You want to optimize loading two fonts in Astro: one for headings and one for body text. You want headings to preload and use display swap, but body text font should load lazily without preload. Which code correctly implements this?

hard

A. import Font from '@astrojs/font';
const headingFont = Font('/fonts/heading.woff2', { preload: true });
const bodyFont = Font('/fonts/body.woff2', { preload: false });

B. import { Font } from '@astrojs/font';
const headingFont = Font({ src: '/fonts/heading.woff2', display: 'block', preload: true });
const bodyFont = Font({ src: '/fonts/body.woff2', display: 'swap', preload: true });

C. import { Font } from '@astrojs/font';
const headingFont = Font({ src: '/fonts/heading.woff2', display: 'swap', preload: true });
const bodyFont = Font({ src: '/fonts/body.woff2', display: 'swap', preload: false });

D. import { Font } from '@astrojs/font';
const headingFont = Font({ src: '/fonts/heading.ttf', display: 'fallback', preload: false });
const bodyFont = Font({ src: '/fonts/body.ttf', display: 'swap', preload: true });

Solution

1. Step 1: Check heading font requirements

   Heading font must preload and use display: 'swap'.

   import { Font } from '@astrojs/font';
   const headingFont = Font({ src: '/fonts/heading.woff2', display: 'swap', preload: true });
   const bodyFont = Font({ src: '/fonts/body.woff2', display: 'swap', preload: false });

   sets preload: true and display: 'swap' correctly.

2. Step 2: Check body font requirements

   Body font should load lazily without preload, so preload: false and display: 'swap' is correct in

   import { Font } from '@astrojs/font';
   const headingFont = Font({ src: '/fonts/heading.woff2', display: 'swap', preload: true });
   const bodyFont = Font({ src: '/fonts/body.woff2', display: 'swap', preload: false });

   .

3. Step 3: Verify other options

   Other options either preload body font incorrectly, use wrong display values, or wrong import syntax.

4. Final Answer:

   import { Font } from '@astrojs/font';
   const headingFont = Font({ src: '/fonts/heading.woff2', display: 'swap', preload: true });
   const bodyFont = Font({ src: '/fonts/body.woff2', display: 'swap', preload: false });

   -> Option C

5. Quick Check:

   Preload headings true, body false with display swap =

   import { Font } from '@astrojs/font';
   const headingFont = Font({ src: '/fonts/heading.woff2', display: 'swap', preload: true });
   const bodyFont = Font({ src: '/fonts/body.woff2', display: 'swap', preload: false });

   [OK]

Hint: Preload headings true, body false; use display swap [OK]

Common Mistakes:

• Preloading body font when it should be lazy
• Using display: 'block' instead of 'swap'
• Incorrect import or function call syntax