Jane Street Interview Process & Prep
Jane Street's process is famously creative. Mental math, market-making games, and puzzle-solving dominate. Coding is OCaml-flavored in production but technical interviews accept Python. The signature round is the mock trading game — practice with real bid/ask spreads, not just textbook problems.
The Jane Street interview funnel
1. Online Assessment
~30 min · probability & mental mathJane Street's first screen is not a coding test. It is a short, timed set of probability, expected-value, and mental-math brain-teasers - prime-sum parity, an optional-reroll dice game, a Bayesian coin re-flip, a two-urn posterior bet - and you explain your reasoning, not just the answer. Quant-research candidates also get a separate live coding round; trading-operations roles get an Excel task.
2. Phone Round 1 — Brain Teasers (the warm-up)
45 min · video callOpening conversational phone round. Three to five brain-teaser / probability questions, intentionally easier than later rounds. They're checking baseline reasoning — does the candidate frame the problem cleanly and think clearly out loud?
3. Phone Round 2 — Brain Teasers (independent batch)
45 min · video callMultiple independent brain-teaser questions back-to-back — they don't build on each other, so you can't lean on context from one problem to the next. Probability-heavy with a sprinkle of game theory or combinatorics. Pacing matters as much as the answers.
4. Phone Round 3 — Hard Probability Deep-Dive
45 min · video call · one problemOne hard probability problem. You'll spend the full 45 minutes on it. Often Markov chains, optional stopping, martingales, or a clever generating-function trick — the kind of problem that doesn't have a clean closed form, where the depth of the conversation is the signal more than the final number.
5. Super Day (Quant Trader) - Morning: Market-Making Games
Onsite - 2-3 live mock-trading gamesThe day opens with two or three live market-making games and this is the real gate. You quote a two-sided market on an uncertain value, the interviewer trades against you, and you update your quotes and manage inventory as order flow arrives. They are watching your number sense, how you price under uncertainty, and how you handle being picked off. A lunch session follows. If the morning does not go well, candidates are usually cut here and do not continue to the afternoon.
6. Super Day (Quant Trader) - Afternoon: Coding & Data Science
Onsite - coding + data-science rounds (if you advance)Candidates who clear the morning games move to the afternoon: hands-on coding problems and data-science / statistics questions (clean implementation, reasoning about data, light modelling). There is no separate final wrap-up - the whole day is one long super-round of back-to-back interviews, and this technical block is the last of it.
Jane Street interview — FAQ
What is the Jane Street interview process?
Jane Street's process is famously creative. Mental math, market-making games, and puzzle-solving dominate. Coding is OCaml-flavored in production but technical interviews accept Python. The signature round is the mock trading game — practice with real bid/ask spreads, not just textbook problems. The loop runs 6 stages: Online Assessment, Phone Round 1 — Brain Teasers (the warm-up), Phone Round 2 — Brain Teasers (independent batch), Phone Round 3 — Hard Probability Deep-Dive, Super Day (Quant Trader) - Morning: Market-Making Games, Super Day (Quant Trader) - Afternoon: Coding & Data Science.
How many rounds does Jane Street have?
6 stages in total, starting with the Online Assessment and ending with the Super Day (Quant Trader) - Afternoon: Coding & Data Science.
How do I prepare for the Jane Street interview?
Work the stage notes above, then drill the Jane Street interview-questions set and the Jane Street online-assessment practice — each problem has a full worked solution.