Polymarket TWAP Resolution: What Changed on 7 August 2026

On 7 August 2026 at 00:00 UTC, Polymarket changed how its crypto Up/Down markets resolve. These markets no longer settle on the asset price at a single instant. Instead they settle on a time-weighted average price - a TWAP - measured across a window leading into expiry. It is the most consequential mechanical change these markets have had, and if any part of your approach was built around the closing tick, it now behaves differently.

The exact specification

The averaging window scales with the length of the market. Five-minute markets settle on a 30-second TWAP. Fifteen-minute and four-hour markets settle on a 60-second TWAP. The averages are computed by Chainlink and delivered through Chainlink Data Streams, alongside Polymarket’s own real-time data service for developers. The change covers the major crypto assets these markets are written on, including BTC, ETH, SOL, XRP, BNB and DOGE. Polymarket also attached a liquidity rewards programme through August to keep order books deep while market makers re-price their models around the new mechanics.

Why a snapshot was a problem

Under the old design, one price at one moment decided a binary outcome worth $1 per share. That is a fragile settlement point. If a market is close to even in the final seconds, a trader with enough capital can push the underlying price on an exchange just far enough, just long enough, to flip the result - and the cost of doing so can be far less than the payout on a large position. Academic work on these markets found this pattern concentrated in the shortest contracts, and materially less present in longer ones, which is exactly the shape you would expect: the shorter the window, the cheaper the manipulation. Averaging across 30 or 60 seconds does not make manipulation impossible, but it forces an attacker to hold the price away from fair value for a sustained period rather than for one tick, which multiplies the capital required.

What this does and does not change for you

Start with what did not change. The base rate did not move. UP versus DOWN was close to even before this change and there is no mechanical reason for the average of a window to be biased where the endpoint was not. Anyone telling you TWAP creates a directional edge is guessing - and as the time-of-day study shows, claims like that need sample size behind them before they mean anything.

What does change is everything keyed to the final instant. A position that was fine because you expected a favourable closing tick is now judged on the average of the last 30 or 60 seconds. Late entries in the closing seconds face an outcome that is already partly determined, since part of the averaging window has elapsed - the market becomes progressively less about what happens next and more about what already happened. And any automated strategy that read a snapshot price to decide its final action is now reading the wrong number.

The honest uncertainty

This is days old at the time of writing, so treat second-order effects as open questions rather than facts. Will spreads widen or tighten as market makers adapt? Will the distribution of near-50¢ closes change now that the endpoint is smoothed? Those are measurable, but only with enough post-change resolutions to say something real - and right now nobody has that sample, us included. We will publish the comparison when the data justifies it, not before. What we can say is that the mechanism is more resistant to a specific, documented failure mode than it was a week ago.

What to do about it

1. Stop treating the closing tick as the decider - the last 30 or 60 seconds are averaged, so a single spike carries far less weight.
2. Re-check any bot or rule that referenced the expiry price; it is now settling against a different number.
3. Keep pricing from base rates on the probabilities page - the resolution method changed, the arithmetic of edge did not.
4. Watch the live windows on the now page for how prices behave into the close under the new rules.
5. Mind your costs. Fees and spread still decide whether a thin edge survives, as covered in fees, deposits and withdrawals.

Integrity upgrades like this one are also the honest answer to the broader question of whether these markets can be trusted at all, which we take apart in is Polymarket legit.