# Polymarket CLOB data explained: prices, liquidity, spreads, and depth

Published: 2026-05-17
Updated: 2026-05-17
Canonical: https://orrery.me/blog/polymarket-clob-data-explained
Markdown: https://orrery.me/blog/polymarket-clob-data-explained/markdown

A market price is only useful when you know how liquid it is, how wide the spread is, and whether the book can support the conclusion.

## Direct answer

- Probability alone is not enough; spread and liquidity explain how trustworthy the displayed price is.
- Thin markets can move dramatically on small trades.
- Liquidity and volume answer different questions.
- A scanner should penalize wide spreads and surface stale or pinned prices carefully.

## Direct answer

Polymarket CLOB data describes the market's tradable structure: displayed probability, bid/ask spread, liquidity, volume, and trade history. A 35% market with tight spread and high volume means something different from a 35% market with almost no depth.

## The order-book reading loop

The safest prediction-market workflow separates attention, evidence, source quality, and next action. A probability move can be important, but it is not useful until the market is liquid enough, the rule is clear enough, and the user knows what to verify next.

- Read probability as the market's current implied price, not as certainty.
- Check spread to see how costly the next trade might be.
- Check liquidity or depth to estimate whether the price is robust.
- Compare 1h, 24h, and 7d movement before calling a move meaningful.
- Look at resolution status before trusting a pinned or stale price.

## What to verify before trusting the move

Good research tools keep the boring details visible. Expiry, resolution source, official status, spread, liquidity, and related markets often explain why a headline probability should be treated carefully.

- Whether the move has volume behind it.
- Whether spread is tight enough for the probability to be meaningful.
- Whether liquidity changed alongside price.
- Whether the market is near expiry or has source ambiguity.

## How Orrery handles it

Orrery's Scanner and Market Detail pages put liquidity, volume, spread quality, movement, confidence, and resolution context next to each other. The goal is to make weak market structure visible before a user overreads a price.

Orrery is not a broker and does not provide trade recommendations. It ranks research work, explains market structure, and keeps resolution rules visible so humans and agents can make better verification decisions.

## FAQ

### Is prediction-market probability the same as forecast accuracy?

No. It is a market price. Accuracy depends on liquidity, participants, rules, and the event itself.

### What does a wide spread mean?

A wide spread usually means the displayed midpoint or last price is less reliable and more expensive to act on.

### Why can a thin market move so much?

Small trades can consume sparse order-book depth and move the displayed price without broad market agreement.

## Related Orrery resources

- [Scanner](https://orrery.me/scanner)
- [Backtest](https://orrery.me/backtest)
- [Signals explained](https://orrery.me/blog/polymarket-signals-explained)
- [Markets API](https://orrery.me/docs/agents/decision-api)
- [Methodology](https://orrery.me/methodology)

Orrery is not affiliated with Polymarket and does not provide investment, legal, or tax advice.