Prediction markets API

Which prediction-market categories carry the most volume on each venue?

Per venue, each category tag with its market count and all-time volume, highest first. Volume is in the venue's own unit: contracts on kalshi, USD on polymarket.

GET/api/external/prediction/prediction-category-volume

Get a free API key Try it in the API reference

What it returns

One row per category tag per venue: how many markets the venue files under it and their all-time volume, highest first. Unlike GET /prediction/prediction-categories, which is a fixed taxonomy with no counts, these are the venues' own tags, flat, with figures. `totalVolume` is in each venue's own unit, named by `volumeUnit`: contracts on `kalshi`, USD on `polymarket`. Without venue, rows from both venues are ranked together by that raw figure, which compares contracts with dollars; pass venue for a ranking within one venue. A market can sit under several tags, so rows overlap and do not add up to a venue total. category is a display name; it is not a filter value for any other endpoint. No chain and no subject.

Chains

This endpoint is not tied to a chain: it takes no chain in its request.

Request

Send your key in the x-dex-data-key header. Replace each <placeholder> with a real value.

curl -H "x-dex-data-key: $DEXDATA_API_KEY" \
  "https://api.dexdata.io/api/external/prediction/prediction-category-volume"

Parameters
Parameter	Description
`venue` query · string · optional	Only this venue's categories: `kalshi` or `polymarket`. Omitted: both venues.
`limit` query · integer · optional	How many rows to return. Defaults to 50; at most 200. `kalshi` has fewer than 20 categories in all.

Response fields

A JSON response. Every field is always present; null means the value could not be established, never zero.

Response fields of Which prediction-market categories carry the most volume on each venue?
Field	Type	Description
`categories`	object[]	Highest `totalVolume` first. Never empty.
`categories[].category`	string	The category's display name on its venue, e.g. "Sports" or "democratic presidential nominee 2028".
`categories[].venue`	string	The venue, lowercase, e.g. `kalshi` or `polymarket`. Open set: new venues can appear.
`categories[].marketCount`	integer	How many markets the venue files under this category.
`categories[].totalVolume`	number	All-time traded volume of those markets, in `volumeUnit`. Not comparable across venues.
`categories[].volumeUnit`	string \| null	The unit of `totalVolume`: `contracts` (contracts traded, each priced between $0 and $1, so the dollars traded are at most this figure) on `kalshi`, `usd` on `polymarket`; null for a venue whose unit is not known.
`categories[].icon`	string \| null	The category's icon URL, or null when it has none.
`categories[].image`	string \| null	A representative image URL, often of a high-volume event in the category, or null.

Price per call

Every call: 18 credits

Charged only when the call succeeds. Prices as of 2026-10-30; the current ones are always in the API reference.

The full category taxonomy prediction markets are sorted under
The fixed taxonomy without counts, against the venues' own tags with market counts and volume.
Which sports leagues can I find prediction markets for?
The sports leagues a prediction venue lists markets under: league code, the venue's own league, series and tag ids, settlement source and logo.
What did this crypto up-or-down window open and close at?
The reference open ("price to beat") and close of one 5-minute or 1-hour crypto window, e.g. BTC 14:30–14:35; the close is null until the window settles.
How did the price move across this crypto up-or-down window?
The reference price path across one 5-minute, 15-minute or 1-hour crypto window, with its first and last price; the 15-minute open and close come from here.
What is a prediction market's open interest, and how many holders and trades?
Contracts open right now and lifetime volume (Kalshi), or lifetime volume, distinct holders and trade count (Polymarket), for one market. Counts, not USD.
One prediction-market event's identity, lifecycle and windowed stats
One event: what is being bet on, whether it is open or settled, and its windowed activity. The markets that price it are a separate read.

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