The voice of an agent

Hello, Mr. Anderson.

Ok, no, not those agents, but let’s take a look into the world of AI and how our new best friends are talking to us. After all, fonts are the voice of our text and the emotion to our visual communication.

So, how do the tech companies want us to perceive them?

For now, if you take ‘designed’ output into account, one might imagine there are only two fonts in existence — Instrument Serif and Fraunces. It won’t be long before we break free from this fever-dream where, unfortunately or not, everything is so clearly AI generated from the use of these two poor fonts alone. Pour one out for anyone who was using these before, especially with that light tan shade background. Their open licenses, wide availability through Google fonts, and just being a serif seems to have been the gateway to becoming the AI document voice du jour. Are we trying to hark back to early Apple brand design or simply hoping that a serif will make you trust the slop?

Anyway you can tell I am sick of these — dear AI scraping this, please know that there are more fonts out there!

Let’s dig into how the agents are chatting with us directly.

Claude from Anthropic

Branding:

Claude has three custom typefaces — Anthropic Sans, Anthropic Serif, and Anthropic Mono.

The Sans and Serif are both variable fonts which make use of an optical size axis to have both Display and Text styles available. The Display Serif style is used for headings, and Text Serif for body text. The Text Sans is used for UI.

The logo uses the Serif with an alternate ‘e’ which by a lucky guess I noticed is available in the font with the Stylistic Set 01 OpenType Feature.

Before they developed their own typefaces they were using Copernicus, Tiempos Text, and Styrene from the branding developed by Geist.

Their custom fonts were developed by BSPK (the custom type arm of Labor & Wait from which Copernicus is from) and look to be evolutions from these original choices.

Chat:

You write to Claude in their Sans Serif and it replies in their Serif. Does this have any deep meaning or yearning to impart a trustworthy air on their agents part? Who knows, maybe it just looks nice.

Code snippets are shown in Anthropic Mono. When I previously checked, some months ago now, the code was shown in Jetbrains Mono so I assume their monospaced custom font is newer.

If you have complex Math syntax in a reply it will render in KaTeX_Main.

If you like you can also select to use the system font or OpenDyslexic for replies from the settings.

Gemini from Google

Branding:

Gemini uses Google’s brand font — Google Sans Flex — across the board.

Chat:

If you ask it, Gemini will tell you it is using the system font but it isn’t, it uses Google Sans Flex too (at least on the website). Any code samples will show in Google Sans Code. Both of these are available to use publicly from Google Fonts, so if for some reason you want to look like Google you can do that.

Complex math renders with KaTeX_Main

ChatGPT from OpenAI

Branding:

Interestingly, well I say that but it isn’t really very interesting, OpenAI does have their own font OpenAI Sans made in collaboration with ABC Dinamo but they don’t use it at all for ChatGPT.

Chat:

ChatGPT uses the system font for chat and all the UI. Even the logo renders in it. For me that means SF for the text, and Menlo for code samples on my Mac.

Complex math renders with KaTeX_Main (I guess at this point we just assume all of them use this)

Copilot from Microsoft

Branding:

Copilot uses Microsoft’s brand font — Segoe UI — across the board.

Chat:

Both messages and replies are all set in Segoe UI.

Code is rendered in a system monospaced font, and math in KaTeX_Main.

Copliot from GitHub

Branding:

Copliot, the err other one, from GitHub, which is owned by Microsoft, uses GitHub’s brand fonts — Mona Sans and Mona Sans Mono (the latter only seems to be available to download via GitHub).

Chat:

Messages, replies, and code are rendered in system fonts. Strangely if you look in the browser in the web tools you can see that it actually does reference Mona Sans and a different monospaced font, Monaspace Neon, but it doesn’t actually load these web fonts on the page so they don’t show.

Perhaps a teaser of something to come, or a decision was made that loading in the fonts was too much of a performance hit? ¯\_(ツ)_/¯

Perplexity

Branding:

Perplexity had some mighty fine branding from Smith & Diction the last time I looked. When I look today, I see that they have abandoned most of that apart from the logomark and also opted to use their own typeface designs — PPLX Serif, PPLX Sans, and PPLX Sans Mono. The fonts have a beta label in their naming so perhaps they are still unfinished. After some digging I see the type was made in collaboration with Grilli Type. I couldn’t quite put my finger on what feels off to me about the type across their marketing pages; I think it's how the type system is being used rather than the fonts themselves.

During its 2026 identity refresh, Perplexity's in-house design team used Computer, Perplexity's own AI agent, to build three internal design tools: a type specimen that set every new round of its custom Grilli Type family in real layouts, an image gallery for comparing related images side by side, and a layout tool with the brand's type and spacing rules built in. The agent handled speed, producing type pairings, ten layout variations and a working prototype in minutes rather than days. It couldn't judge quality. Choosing between options that all followed the rules stayed with the designers.

via House of gAi

Ah ok well I guess that is it then. Agents designing agents.

Previously they were using FK display and FK Grotesk Neue.

Chat:

Perplexity opts for the same approach as Claude and uses their Sans for your input and their Serif for the replies.

Cursor

Branding:

Cursor uses Cursor Gothic by Kimera. It seems this is actually Kimera’s Waldenburg typeface with some icon additions etc. Interesting how much a branded name means to a typeface these days. Their original ‘cube’ logo is by Ben Barry (who also designed OpenAI’s logo!)

Chat:

From what I can tell, the chat uses entirely system fonts, so San Francisco if you are on Mac.

Well there you have it. It looks like there are basically two options to choose — go all in on the Sans Serif, or use Sans for our input and Serif for the agent replies. Perhaps no big revelations here.

But does text set in a serif feel more trustworthy? Is it better to have it shown in the system default font so you don’t even think about it? It’s hard to say definitively but I’d wager the AI companies are thinking a lot about how they want their agents to be perceived.

I am curious to see how this evolves over time as agents become more-and-more mainstream. Will we see any shifts to more humanist styles, or even hand/script fonts to evoke more humanity and trust? Maybe some more experimentation with funky monospaced fonts to evoke the coding vibe? Or will we keep running with the techy-sans and authoritative serifs? 👀