Polymarket

How we read it

Predictmoni reads Polymarket prices from its live order book, not from a listed price.

Polymarket is a peer-to-peer prediction market built on Polygon. It describes itself as the world's largest prediction market ^[1].

Where does Polymarket get its prices?

Polymarket prices come from a central limit order book. Traders post bids and asks, and a price between $0 and $1 reads as a probability.

Polymarket does not set prices. They come from supply and demand between users on its Central Limit Order Book ^[2].

A share priced at $0.25 implies a 25% chance ^[2].

Why doesn't Predictmoni use Polymarket's displayed price?

The displayed price is a midpoint, or the last trade when the spread is wide. Neither is a price you can buy at right now.

Polymarket displays the midpoint of the bid-ask spread. When the spread is wider than $0.10, it shows the last traded price instead ^[2].

A buyer pays the ask. A seller receives the bid ^[2].

Predictmoni uses the best bid and the best ask for that reason.

How is the Polymarket order book sorted?

Polymarket's book endpoint lists bids from lowest to highest and asks from highest to lowest. The best prices sit at the end of each list.

In a book read on 2026-09-25, the first bid was $0.001 and the first ask was $0.999 ^[3].

Reading the first entry of each list would invent a spread of almost a dollar on a healthy market.

Predictmoni takes the highest bid and the lowest ask by value, not by position.

Fees

Polymarket charges a taker fee on some markets. Makers are never charged ^[4].

Taker fees fund a maker rebate program. Polymarket pays those rebates daily in pUSD, with a $1 minimum payout ^[6].

How much does Polymarket charge per trade?

Polymarket charges takers a fee equal to shares times rate times price times one minus price. Rates range from zero to 0.07.

The formula is fee = C × feeRate × p × (1 − p). C is the number of shares and p is the share price ^[4].

Crypto markets use a rate of 0.07 ^[4].

Sports, economics, culture, weather and other markets use 0.05 ^[4].

Finance, politics, mentions and tech markets use 0.04 ^[4].

Fees are rounded to five decimal places. The smallest fee is 0.00001 USDC ^[4].

Each Polymarket market also publishes its own rate, and it can differ from this table ^[5]. On 2026-09-25 an NFL championship market listed a sports rate of 0.03 ^[10].

Where the Polymarket fee peaks

The dollar fee peaks at a 50-cent price and falls toward both ends. A 30-cent trade costs the same as a 70-cent trade ^[4].

On 100 crypto shares, the taker fee is $1.75 at 50 cents ^[4].

The same 100 crypto shares cost $0.07 in fees at 1 cent ^[4].

On 100 politics shares at 50 cents, the fee is $1.00 ^[4].

Are any Polymarket markets fee-free?

Yes. Polymarket charges no trading fee on geopolitical and world events markets, and it charges nothing to deposit or withdraw USDC.

Polymarket says it does not charge fees or profit from trading on geopolitical and world events markets ^[4].

Intermediaries such as Coinbase or MoonPay may still charge their own fees ^[4].

How Predictmoni finds the fee on a Polymarket market

Predictmoni reads each Polymarket market's published fee schedule first. It uses Polymarket's category rate only when a market publishes no schedule.

Each Polymarket market carries a feesEnabled flag and a feeSchedule object with a base rate ^[5].

A guessed rate can be too low. A fee that is too low makes a price gap look bigger than it is.

Where it appears on this site

Polymarket appears on Predictmoni in three places: copy trading, trader analysis and the price-gap board.

Predict.fun is the other venue where Predictmoni copy trading runs. The venue index has notes on every venue we read.

Copy trading on Polymarket

Predictmoni copy trading runs on Polymarket and Predict.fun. Other venues appear on Predictmoni for price comparison or analysis only.

Predictmoni ranks the best Polymarket traders on its trader analysis page.

How does Polymarket feed the price-gap board?

Every curated pair on the price-gap board has one leg on Kalshi. Most of the other legs are Polymarket markets. No pair uses Opinion.

A few curated pairs use a Limitless leg in place of Polymarket.

The live gaps are on the prediction market arbitrage board.

Quirks worth knowing

Polymarket's quirks sit in how markets resolve and in how its API returns data.

How does Polymarket settle a market?

Polymarket settles markets through UMA's Optimistic Oracle. Anyone can propose an outcome by posting a bond, and anyone can dispute it.

A proposer typically posts a $750 pUSD bond ^[7].

A two-hour challenge period follows each proposal ^[7].

If a second proposal is also disputed, UMA token holders vote on the result ^[7].

An undisputed market resolves about two hours after the proposal. A disputed one takes four to six days ^[7].

Winning shares redeem for $1 each. Losing shares are worth nothing ^[7].

Does a Polymarket market title tell you how it resolves?

No. The title describes the question, but the market's written rules decide how it resolves. Polymarket tells traders to read the rules first.

Each market's rules name a resolution source, an end date and how edge cases are handled ^[7].

Polymarket can add a clarification after trading starts. A clarification cannot change the question's intent ^[7].

For a price gap this matters most. Predictmoni compares the rules of both markets, not their titles.

Missing tags in Polymarket's market data

Polymarket's Gamma API leaves tags out of a market unless the request asks for them. Code that expects tags can silently misread the category ^[8][9].

The same market returned no tags without include_tag=true ^[8].

With include_tag=true it returned five tags, including Geopolitics ^[9].

Fee rates differ by category, so a missing tag can lead to the wrong fee ^[4].