A world-class tutor in every home

Introducing Koji, the world's first graphical tutor. 

Private tutoring has been the most effective form of instruction for millennia, but it has been reserved for an elite few. We built Koji for everyone else.

Koji asks instead of tells, builds confidence instead of dependency, and never, ever just hands you the answer.

Years of infrastructure, compounding

Koji is the result of years of careful, methodical work. The same technical building blocks that have allowed us to scale interactive learning, along with our learning data, are what make Koji uniquely possible.

Lessons on Brilliant are interactive, visual, and hands-on. You learn about derivatives by dragging the tangent line and watching the slope change. Each lesson and every user interaction is built from blocks of code.

Koji "speaks" our lessons and interactives. He can see what's on your screen – every choice you've made, every place you've paused. He knows exactly why you are stuck. And he’s tied to our infrastructure in ways that ensure accuracy.

Koji tutors like the best

Learning with Koji is like having an infinitely patient tutor sitting next to you, drawing on the paper with you to clear up any confusion.

Most AI tools just give students the answer, robbing them of the chance to learn and making them dependent. That’s why the mark of a great teacher isn't how well they can explain the answer. It’s making the student feel seen while they do the thinking themselves.

That philosophy shaped how Koji behaves, down to the exact words he uses.

Because Koji can see everything the happens in the lesson, he can also reach into it and adjust it — highlighting a region, annotating a graph, or posing an intermediate interactive question. That’s what real, effective tutoring looks like.

Ultimately, the goal is for Koji to make himself unnecessary. Koji offers more help when you’re doing conceptual learning, and steps back as you reach mastery. His job is to gradually hand the thinking back to you, until you're the one asking yourself the questions he used to ask.

Koji speaks first

One of the things we got wrong early on was assuming Koji's voice would be a nice-to-have. In our testing, it turned out to be essential.

When a tutor speaks to you before you ask for help, it dramatically lowers the barrier to asking. So today, by default, Koji speaks at the start of every lesson page – not reading the instructions aloud, but noticing things: what changed from the last problem and what's worth paying attention to before you try.

Koji had to be Koji

More than once, we considered removing Koji (the character) entirely. We were worried a cute mascot would make it seem like it wasn't built for serious learning.

But, user interview after user interview, with nothing but a sparkle button, the students kept asking for a character.

People don't want to talk to a generic sparkle button. And they try harder when they feel like someone is looking, so Koji is designed to be the kind of presence that makes you more willing to try, fail, and ask the questions you were afraid to ask.

We’re just getting started

We spent a long time building a tutor we wished existed. Nobody could prepare us for the magic of how it makes people feel.

Koji is available in most of our math and coding courses, with more on the way. He can speak in almost any language, and deeper multilingual support in-lesson is coming soon. 

Next up: Koji's will be able to tutor you on your specific school assignments and be your guide across your larger learning journey.

If you're excited about what it takes to build something that actually helps people learn, and curious about what comes next, we're hiring.

There's a lot more Koji left to build.