What Font Does Bluesky Use? Inter, System Fonts, and the AT Protocol

TL;DR: Bluesky uses Inter as its default font on the web app (bsky.app) and in its iOS and Android apps. A setting lets you switch the app to your device's system font instead. There is no built-in bold or italic for posts, and no way to pick a font that other people see.

Bluesky has grown from a small invite-only experiment into a real alternative to X, and with that growth comes a question designers and curious users keep asking: what font is that? The answer is straightforward, and because Bluesky is open-source, you can verify it yourself.

The Bluesky web app font: Inter

The primary typeface on bsky.app is Inter, a free and open-source sans-serif designed by Rasmus Andersson. Inter was originally created for computer interfaces, with a tall x-height and open apertures that keep text readable at small sizes on screens. It ships in variable-weight format, covering everything from Thin (100) to Black (900).

If you open bsky.app in a browser and inspect the CSS, the font stack looks like this:

InterVariable, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji"

Inter does the heavy lifting for post text, profile names, navigation labels, and buttons. The system-ui fallbacks exist for situations where Inter has not loaded yet or for characters Inter does not cover.

You can confirm this yourself. Bluesky is built on React Native for Web using the social-app repository on GitHub. The font declarations live in the theme files. Because everything is open-source under the MIT license, there is nothing hidden about the choice.

Why Inter?

Inter is one of the most widely used UI fonts on the web. It became popular because it was purpose-built for interfaces rather than adapted from a print typeface. A few qualities make it a natural pick for a social platform:

• Legibility at small sizes. The tall x-height and generous letter spacing mean short posts, timestamps, and follower counts stay crisp on high-density screens.
• Variable font support. A single variable file covers all weights, so Bluesky can use semibold for usernames and regular for post body without loading multiple font files.
• Free and open-source. Inter is released under the SIL Open Font License, which means zero licensing cost and no usage restrictions. For a startup building an open protocol, that matters.
• Neutral personality. Inter does not call attention to itself. It gets out of the way and lets the content (your posts, images, links) do the talking.

What about the mobile apps?

The iOS and Android apps use Inter too. Bluesky's apps are built with React Native, and the app bundles Inter and applies it by default, which Bluesky calls the "theme" font.

In Settings > Appearance > Font you can choose between Theme (Inter) and System, your device's own font, such as SF Pro on an iPhone or Roboto on most Android phones. Bluesky recommends the theme font "for the best experience". The same screen also has a text size setting.

These settings only change what you see. Someone reading your post on another device sees it in their own font setting. If you have used other social platforms, compare X (Twitter), which uses its custom Chirp typeface, and Mastodon, which uses Roboto on the web.

The AT Protocol and Bluesky branding

Bluesky the app and the AT Protocol (the decentralized protocol it runs on) are related but separate. The AT Protocol documentation and branding have their own visual identity, distinct from the social app. The Bluesky butterfly logo is a custom graphic, not a font, so you won't find it in a font library.

For the app interface itself, it's Inter everywhere unless you switch to your system font. There is no secret brand typeface hiding behind the scenes.

Can you change the font on Bluesky?

Only for yourself. The Appearance settings let you switch between Inter and your system font and change the text size, but that changes how Bluesky looks to you, not how your posts look to anyone else. There's no font picker or formatting toolbar in the compose box, and posts are plain text.

So how do people post text that looks bold, italic, or styled in unusual ways? The same way they do it on every other platform that lacks native formatting: Unicode look-alike characters.

Unicode includes separate code points for mathematical bold letters (like 𝐁𝐥𝐮𝐞𝐬𝐤𝐲), italic letters, script letters, and dozens of other decorative alphabets. A text generator or font generator converts your plain text into these look-alikes, and you paste the result into Bluesky. The app displays them because they are standard Unicode, not because Bluesky has any special formatting support.

Our Bluesky text formatter is built for exactly this. Pick a style, type your text, copy the output, and paste it into your Bluesky post or bio.

But know the trade-offs before you go wild:

• Screen readers struggle with Unicode styled text. Many assistive technologies skip or mangle these characters. If accessibility matters to you (and it should), use Unicode styling sparingly. We wrote a full breakdown in are Unicode fonts accessible?
• Search does not work. A post written in 𝕌𝕟𝕚𝕔𝕠𝕕𝕖 𝕕𝕠𝕦𝕓𝕝𝕖-𝕤𝕥𝕣𝕦𝕔𝕜 letters will not show up when someone searches for the plain-text version of those words.
• Some characters may not render. If a reader's device lacks the right Unicode block, styled characters can appear as empty boxes. See why fancy text shows as boxes for more on that.
• Hashtags and mentions break. A hashtag written in Unicode bold will not function as a clickable tag.

A bold name in your display name or a single styled word in a bio? Fine. An entire post in cursive Unicode? That is going to hurt readability more than it helps.

How does Bluesky compare to other platforms?

Here is a quick comparison of the interface fonts on Bluesky and two alternatives:

Bluesky and Mastodon both picked widely available, open-source fonts for their web UIs. X went the custom route with Chirp.