What you may do with a venue's prices once you have them

A prediction market's prices are unusually easy to get. Several venues answer market-data requests without a key, and the numbers are on the front page of the website. That makes it easy to forget that getting a price and being allowed to use it are two different questions, answered by different documents. This page is about the second one.

How it works

Four documents, four audiences

Who may do what with a venue's prices is decided by whichever of these binds you, and they bind different people:

• the exchange rulebook binds members, the accounts that trade;
• the API or developer agreement binds anyone who calls the API, member or not;
• the website terms bind anyone who visits;
• a distribution agreement binds a licensee who resells the data.

One person can be bound by three of them at once. A member who builds a dashboard on the API and publishes it on the web is under the rulebook as a trader, the developer agreement as a caller and the site terms as a visitor, and the narrowest of the three is the one that bites.

The floor the law sets

For a US designated contract market, some data is public by regulation. 17 CFR 16.01 requires each reporting market to record, for every business day, total trading volume and open interest, and to make them "readily available to the news media and the general public without charge" no later than the business day after the day they describe. It must also make its opening and closing prices, the price used for settlement where different, and the day's high and low "readily available to the news media and the general public" by the same deadline.

Polymarket US's rulebook, dated 30 September 2026, implements this in Rule 5.10: the exchange "will post on its website the pricing, current volume and open interest for all active Contracts on each Trading Day". That is the floor. It is daily, not live, and it covers the figures the regulation lists, not the order book.

Venues that are not designated contract markets, such as Manifold, have no equivalent obligation.

What an exchange keeps for itself

Above the floor, both US exchanges read for this page assert control over everything else.

Kalshi's rulebook, version 1.29, says in Rule 11.1(b) that Kalshi "is the owner of all rights, title and interest in and to all intellectual property and other proprietary rights ... in market data, and all derivative works based thereon". Participants, the rulebook's word for members, brokers and brokers' customers alike, may use market data "for their own internal business purposes" and "may not distribute, sell or retransmit market data ... to any third party". Rule 11.1(d) adds that transaction data may be disclosed publicly only in aggregated or anonymous form.

Polymarket US's rulebook reserves the distribution to the exchange in Rule 5.3(f), which lets it make order and trade information available "through the Trading System, a ticker, financial information services or otherwise", and closes the door behind it in Rule 5.3(g): "Any Person receiving information through the Trading System is expressly prohibited from redistributing such information unless expressly permitted by the Company."

What Polymarket US's API sends is also narrower than a reader might assume. Its market data guide says the order book is aggregated by price level, that full depth needs a separate read:l2marketdata scope, and that there is no public trade tape: "Trades are not disseminated via market data APIs." The one exception it documents is the RFQ trade history, anonymous prints of fills that began as a request for quote, which "all participants see".

What an API key allows

Kalshi's developer agreement, version 1.1, binds "any user" of the API and takes effect on first use. Its prohibitions section opens: "Use of Kalshi APIs is expressly limited to facilitating a members own trading on the Exchange; all other usages are disallowed and may result in account suspension." It then lists, among others:

• collecting, caching, aggregating or storing data accessed via the API "except for purposes of facilitating your own trading on Kalshi", and sharing it with third parties "in any manner without prior written authorization from Kalshi" (3.1);
• accessing the API to monitor Kalshi's services "or for any other benchmarking or competitive purposes" (3.5);
• sublicensing the API to a third party (3.7).

Section 6.4 requires prior written approval for public statements and promotional material relating to Kalshi or its API. Section 2.1 reserves the right to update the agreement at any time. The copy read for this page is the PDF in Kalshi's public document store, marked v1.1; Kalshi's developer-agreement web page did not load from here, so a change made only there would not be reflected above. The practical effect on a public chart is worked through in embed a live market chart on your website.

A market-data endpoint that answers without a key does not change any of this. The agreement attaches to use, not to authentication.

What a website's terms allow

Manifold's terms, last updated 31 January 2026, grant a "limited license to access and use the Site ... solely for your personal, non-commercial use", and forbid copying, republishing or publicly displaying content "for any commercial purpose whatsoever, without our express prior written permission". Among the prohibited activities: to "systematically retrieve data or other content from the Site to create or compile ... a collection, compilation, database, or directory without written permission", and to scrape the site "through any means other than our public API". Training commercial AI models on Manifold data requires a data licence; "academic research, personal projects, and non-commercial use are permitted."

Who sells it

On 7 October 2025 Intercontinental Exchange announced an investment of up to $2 billion in Polymarket and said it would become "a global distributor of Polymarket's event-driven data", providing customers with sentiment indicators on topics of market relevance. The release is the whole of what is public about that arrangement: it does not give prices, exclusivity or what a licensee may pass on. What it does establish is that redistribution of Polymarket's data to ICE's customers is a product with a distributor, not something the public API was built to serve.

Where showing a price is itself the problem

In one jurisdiction, display carries a penalty of its own. France's gaming authority, the ANJ, in its notice of 17 July 2026 ordering internet providers to block Polymarket, called the site's live homepage prices "un vecteur majeur de diffusion et de promotion" of an offer not authorised in France, and set out the law: publicity for an unauthorised site is an offence punishable by a fine of €100,000, and the same penalty applies to anyone who publicly disseminates the odds and payout ratios such a site offers "aux fins de promouvoir" unlicensed online sites. The test in that sentence is promotion, not display as such, and how it applies to a neutral data page is not something the notice addresses. Why Europe blocks event contracts covers the rest of that regime.

What you can do about it

Name your use before you read the terms. Your own trading; internal analysis inside a firm; showing prices to the public; passing data to someone else; selling it; training a model. Every document above draws its lines between those uses, and the answer for one says little about the next.

Start from what is public by regulation. If daily settlement prices, volume and open interest from a US exchange are enough for the job, 16.01 requires them to be published, and the exchange's own daily posting is the source to cite.

For public display, use the venue's own display product where it has one. Polymarket Embeds is a widget the venue offers for exactly that; Kalshi documents none, and its agreement asks for written authorization first. The embed how-to compares the routes.

Ask in writing, and keep the answer. Both Kalshi documents and Polymarket US's rulebook leave the door open on the same condition: the venue's express permission. An email that says yes is the only thing that turns a prohibited use into a permitted one.

For a commercial feed, go to whoever is allowed to sell it. For Polymarket that includes ICE, per its own announcement; for any venue, the venue itself. A third-party API that resells a venue's prices is only as licensed as its own agreement with that venue, and the market data APIs cards say where each one gets its data.

Record the version you relied on. Kalshi's agreement reserves the right to change at any time, Manifold's terms say continued use after an update is acceptance, and a rulebook is refiled whenever the exchange changes it. Keep the version number or the date, as this page does.