Jane Street Interview ProcessTier 0
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.
Pre-interview Assessment (some cycles)
Jane Street's screen is built around probability, expected value, and mental math, not algorithmic coding. The first-round assessment is a short set of brain-teasers where your reasoning matters as much as the number; a separate quant-research round adds a live coding exercise, and trading-operations roles get an Excel-based task.
Practice this round 4 problems ProA short, timed set of probability, expected-value, and mental-math questions (prime-sum parity, an optional-reroll dice game, a Bayesian coin re-flip, a two-urn posterior bet, plus counting and estimation). You explain your reasoning, not just the answer.
Take the timed assessmentReal reported OA questions, on the clockProA second-round live coding exercise for quant-research candidates - a clean implementation problem (not LeetCode trickery), with follow-ups on efficiency and on shaping the code into a reusable library.
Gravity Grid k-in-a-RowSimulate a grid where pieces enter at the bottom and push the column up, then detect a k-in-a-row win horizontally or vertically.Candidates describe the Jane Street online assessment as a written or HackerRank-hosted set of about 4 questions in 30 minutes for the Trader, Quant Trader and Research tracks. The questions are probability, expected value and mental math (a prime-sum parity count, an optional-reroll dice game, a Bayesian coin re-flip, a two-urn posterior bet, plus counting and estimation), and you are asked to explain your reasoning, not just type the number. There is no algorithmic coding on the first-round screen: the quant-research track adds a separate live coding round, and trading-operations roles get an Excel-based task instead. Our timed replica runs 8 questions in 30 minutes; the first four follow the recurring Trader / QT template and the rest are the mental-math questions, answered as a reduced fraction or a decimal.
Work the reported question families above with a full solution each, then take the timed replica so the 30-minute pace is automatic. Because the screen asks for your reasoning, practise writing a two-line justification for every answer rather than only the value. Three families carry the screen: expected value of small games, Bayesian updates on coins and urns, and fast counting; the topic hubs below cover each with worked solutions. For the puzzle-style thinking Jane Street is known for, the puzzles guide is the natural complement, and the interview-process page shows what follows a pass.
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Every firm has a curated interview-questions playlist — a ready-to-drill set of problems matched to how that firm interviews, each with a full worked solution.
Practice every firm's OA: timed replicas, free game replicas and guides in one place →
Jane Street round-by-round guides
Jane Street interview guide: the firm, culture, roles and pay →
Stage guides for every firm: superdays · behavioral questions · market-making games
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: Pre-interview Assessment (some cycles), 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 Pre-interview Assessment (some cycles) 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.