What font does Claude use?
Claude is one of the few AI products that leads with a serif, which gives it a bookish, human tone. We inspected the logged-out sign-in page, since the app itself needs an account. The same two families appear on anthropic.com.
Short answer: Claude’s web app uses two custom variable typefaces: Anthropic Serif for headlines and Anthropic Sans for interface text. Both are served from an Anthropic asset domain.
Anthropic Sans
Self-hosted74.9%- CSS name
anthropic-sans- Weights
- 400, 500
- Sizes
- 15px · 12px
- Served from
- assets-proxy.anthropic.com
Anthropic Serif
Self-hosted25.1%- CSS name
anthropic-serif- Weights
- 300, 400
- Sizes
- 56px · 18px
- Served from
- assets-proxy.anthropic.com
Sizes, weights and spacing by role
These are computed values from the live page, which is what the Font Inspector panel shows when you click each element.
| Role | Font | Size | Weight | Line height | Letter spacing |
|---|---|---|---|---|---|
| Headline | Anthropic Serif | 56px | 300 | 1.15 | normal |
| Subheading | Anthropic Serif | 18px | 400 | 1.38 | normal |
| Button | Anthropic Sans | 15px | 400 | 1.47 | normal |
| Small text | Anthropic Sans | 12px | 400 | 1.63 | normal |
The main font stack in the CSS:
font-family: anthropic-serif, "Anthropic Serif Fallback Georgia", "Anthropic Serif Fallback Times", Georgia, serif;- The CSS drives the variable axes directly: the headline sets
wghtto 290 andopszto 48, and interface text setswghtto 360. Those are lighter than the standard 300 and 400 stops. - A grade axis,
GRAD, is present and set to 0. Grade changes stroke thickness without changing letter widths, which is useful for dark mode. - The stack lists several generated fallback faces, such as “Anthropic Serif Fallback Georgia”, each tuned to keep the layout stable on a different operating system.
Check any site yourself in one click.
Sites change their type without notice. Font Inspector shows the rendered font, size, weight and spacing of any text on claude.ai or anywhere else, and lists every font on the page. Free, no account.
About the fonts, and whether you can use them
Anthropic Sans
Anthropic’s own sans serif, a variable font covering weights 300 to 800. It sets buttons, labels and small print.
Can you use it? It is a proprietary brand typeface and is not available to license. Open source sans serifs such as Source Sans 3 and Figtree sit in similar territory.
On Google Fonts: Source Sans 3, Figtree.
Anthropic Serif
Anthropic’s own serif, also a variable font, with weight, optical size and grade axes. It sets the large greeting and the tagline.
Can you use it? Also proprietary. Newsreader and Source Serif 4 are free text serifs with optical sizes that give a comparable warm, editorial voice.
On Google Fonts: Newsreader, Source Serif 4.
Finding a font does not license it. More in how to get a font you found, legally.
Get a similar look with a free font
This starter uses Newsreader, which is open source, with the sizes and spacing measured above. It is an approximation, not a copy of Claude’s brand typeface.
/* Approximates the Claude look with a free font */
body {
font-family: "Newsreader", Georgia, "Times New Roman", serif;
}
h1 {
font-size: 3.5rem; /* 56px */
font-weight: 300;
line-height: 1.15;
}How we checked
We opened claude.ai in Chrome on September 20, 2026 and read the computed styles of its visible text: the declared font stack, the font actually rendered, and how much of the page’s text each family sets. That is the same data the Font Inspector extension shows under Fonts on this page. We re-check these pages periodically, and the date above shows the last inspection.
Claude and its typefaces are trademarks of their respective owners. Font Inspector is not affiliated with Claude.
Questions & answers
What font does Claude use on its website?+
Claude’s web app uses two custom variable typefaces: Anthropic Serif for headlines and Anthropic Sans for interface text. Both are served from an Anthropic asset domain.
Can I use the Claude font?+
It is a proprietary brand typeface and is not available to license. Open source sans serifs such as Source Sans 3 and Figtree sit in similar territory.
What is a free font similar to Anthropic Sans?+
Source Sans 3 and Figtree are free on Google Fonts and give a similar feel. No free font is an exact match, so compare it with your own text first.
How can I check what font Claude uses myself?+
Open claude.ai, then click any text with the Font Inspector extension, or right-click, choose Inspect and look at Rendered Fonts in the Computed tab. Sites change their typography, so checking the live page is the only way to be sure.