Polymarket Current Prices

• The mid — the average of the top bid and ask — is the headline number dashboards show, updated continuously by the official book feed.
• The last price — the most recent fill — is what a ticker renders, and it lags the ladder whenever fills pause.
• The executable floor — the best resting level you can actually hit — is the only honest price for a market order, and the official /book endpoint returns the whole ladder.

• Official: GET a market slug on the free public API returns the current book with bid, ask, last, and volume; no key required for the public feed.
• Archive: GET the market's latest frame at 250ms for the same three numbers plus the full depth that day.
• Paid feeds: the 250ms archive streams to apps and sheets for the freshest measure of all three, historical and live.
• Every source has a timestamp; any "current price" without one is not auditable, and the archive is build on auditability.

All three numbers converge on liquid markets and diverge exactly when it matters: on a one-sided repricing, the mid and last can sit on a ladder that already jumped (a 99.6-cent move in one recorded second), while the floor is the number that would have cut the loss.

The measured book shape — 90%+ one-sided frames, 98.6% at 0.99/0.995 — means the difference between mid and floor is the difference between a headline and an executable order.

• At 14:00 UTC on a liquid crypto market: read the mid, last, and executable floor from the official /book, then pull the archive frame at the same second and confirm all three agree.
• Log the delta over a reprice window (the recorded 65-second ETH move is a clean case): note how often mid and floor actually diverged — that delta is the honest cost of trading the headline.
• Build a small watchlist table (slug, mid, last, floor, ts) refreshed per minute; 1,440 rows a day and it becomes your own current-price history.
• Add a stale-check column: if the floor has moved but the mid has not, flag it; the flag is your early-warning for a repricing ladder.

Current prices are three numbers because the venue has three realities: the headline mid, the last fill, and the executable floor — and the archive exists precisely to keep those three honest hour after hour.

The divergence is the information: on a book that is one-sided 90%+ of the time, the floor is the executable fact, and a dashboard that shows only the mid has hidden the market from its own users.

Any "current price" you publish carries a timestamp in the archive by construction; a price without a time is not data, it is a screenshot.

In a feature or report, current prices render from the live feed while the archive proves them on demand — the pairing that makes a quote dashboard verifiable.

Use the floor as the tradable column and the mid as the display column, and record both every time; that one habit is the whole honest-price practice in miniature.

The honest current price is the executable floor sitting under the headline, measured at a timestamp the archive can reproduce.

Decide which of the three numbers your interface is showing and log the other two; divergence is where the information actually lives.

Free tiers cover everything described here; depth and history tiers add the record longer than three days when the study demands it.

The audit step for any current-price claim: pull the archive frame at the claim's timestamp and confirm the mid, last, and floor match what was displayed. Run it once a day on a sample and the audit becomes part of the routine, not an afterthought.

An alternative that costs nothing: always keep the floor and mid columns in the same table as the display copy, so a reporter or user can ask "was that executable?" and the answer is one query away.

That is the practical endpoint of this page: current prices with provenance, three numbers measured against the record, and the free tier as the floor for every one of them.

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