Polymarket vs Sportsbook
Polymarket vs Sportsbook Odds
A sportsbook sets odds and books action against a house edge; Polymarket hosts a binary order book where bettors are the counterparties. This page maps the two on vig, liquidity, cadence, and — the part most comparisons miss — what each leaves behind as historical data.
Figures measured as of 2026-09-24 on the published PolyOrderbooks archive.
Short answer
Bookmaker versus exchange
The sportsbook profit model is the vig: it prices a two-way event at over 100% implied probability and profits from the margin. Polymarket lists binary markets where YES and NO trade as contracts between orders; the venue's spread is whatever the resting book says, fee-free.
The match-price consequence is real: a binary market mid is a probability that you can also express as decimal odds, and on a thin one-sided Polymarket book the executable price sits on the winning side while nobody quotes the other.
Vig
Where the margin lives
Sportsbooks skim a vig per market, typically 4-6% on two-way lines. Polymarket charges no trading fee; the practical cost is spread and slippage inside books that are one-sided 16.9% of the time at 5-minute granularity and crossed 3.24% of snapshots.
So the honest "fee comparison" is: a sportsbook's vig is fixed and known, while Polymarket's cost is variable and only visible in the ladder. That is precisely why this site records the ladder — cost cannot be reasoned about without it.
Cadence
Movement and freshness
Sportsbook lines move when the book wants them to move — on sharp money, steam, and scheduled prices. Polymarket books reprice on event ticks: a kickoff, a basket, a reference print, with trades tracked in time to the UTC second and books stored at 250ms.
The freshness difference is the data difference: a closing line is a daily artifact, while a recorded Polymarket book is a 250ms artifact you can replay from open to settle.
Data
The historical record
Sportsbook closing lines are widely licensed and reasonably coarse; full in-play depth is usually not exported. Polymarket's official API is free for live state, and its recorded depth is served here at 250ms with prices, metrics, and resolved outcomes — the raw material for fill-level sport backtests.
The sports catalog on this site (700k+ markets, 226 series) makes the venue comparable to a bookmaker at scale, while the archive keeps the individual game's book for later study.
Honest pick
Which to choose
Choose a sportsbook for parlay-style wagering, lines, and phone-betting rails. Choose Polymarket when you want fee-free binary pricing, sub-second freshness, and an order book you can backtest.
On the data axis the comparison is not close: only one side captures the full book at 250ms, and that side is the venue this site archives.
FAQ
Does Polymarket have a vig?
No trading fee, so no built-in vig. The venue's cost is the spread on its order book, which is measurable from stored 250ms books.
How does Polymarket pricing compare to Vegas?
Both express probability, but a sportsbook prices to a margin, while Polymarket prices emerge from resting limit orders that can be one-sided near settlement.
Can I get historical in-play Polymarket data?
Yes — recorded full L2 books at 250ms with prices, metrics, and outcomes, plus free live 1-minute price history from the official API.