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 is fluent in our lessons and interactives. He can see what's on your screen. He can see your wrong guesses or where you paused to think, and uses that information to figure out exactly why you are stuck. And we've built technology under the hood to ensure that his responses are accurate.

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 explain the answer to students, which robs them of the chance to learn and making them dependent. This isn’t what great tutors do. They instead focus on making the learner 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 that 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. We've found this to be much more effective than text explanations.

Ultimately, the goal is for Koji to make himself unnecessary. Koji offers more help when you’re learning a new topic, and steps back when it's time to test your knowledge. Koji’s job is to provide handholds to help you climb on your own, until you don't need the help at all.

Koji speaks first

Early on, we assumed that having Koji speak out loud would be a nice-to-have feature. 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 generic sparkle button, the students kept asking for a character they could talk to.

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've spent a long time building the tutor we always wished existed. It's already been enormously gratifying to see students find joy in using it to overcome challenges.

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 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.