The Best Prediction Market Data APIs in 2026

The state of prediction market APIs in 2026

A few years ago, if you wanted prediction market data in a usable form, your options were limited. You could scrape pages, deal with unofficial endpoints, or use a half-documented API that might change without notice. It wasn't great.

That's changed. The platforms have matured. Several have invested in proper developer tooling. And a new category has emerged: unified data providers that normalize and aggregate data across platforms so developers don't have to build that infrastructure themselves.

This post covers the main options in 2026 — direct platform APIs and unified providers — and helps you think through which makes sense for what you're building.

Direct platform APIs

If you only need one platform, going direct is often the right call. Here's where each major platform stands:

Polymarket is the most developer-friendly of the direct options. It has a well-documented REST API, good volume on political and macro markets, and an active developer community. If you're building something that only needs Polymarket data, start here.

Kalshi is a regulated US exchange, which matters for some use cases. Its API is functional, though the documentation is more focused on trading operations than raw data access. Getting started takes a bit more setup than Polymarket.

Novig has grown quickly in sports prediction markets. The API is still maturing, but it covers markets that the other platforms don't, particularly around live sports outcomes.

PredictIt and Metaculus have APIs but are less actively developed from a data-access perspective. PredictIt has regulatory constraints. Metaculus is oriented more toward community forecasting than trading.

The limitation with any direct approach: you're locked to one platform's schema, one platform's data, and one platform's reliability. Adding a second platform means starting over.

Unified prediction market data APIs

Unified providers aggregate data from multiple platforms, normalize it to a consistent schema, and expose it through a single endpoint. You write one integration, and you get data from everywhere they cover.

This is a relatively new category. A few years ago, the main option was to build it yourself. Now there are providers specifically focused on this problem.

The key things to evaluate when comparing unified providers:

Platform coverage: Which platforms do they cover? Are those the platforms you care about? A provider that covers Polymarket and Kalshi but not Novig might not be enough if you're focused on sports markets.

Data freshness: How frequently does data update? For time-sensitive use cases like arbitrage scanning, this matters a lot. Real-time or sub-minute updates are meaningfully different from 5-minute polling.

Historical data: Is historical data available? For backtesting or ML training, you need resolved markets. Not all providers offer this, and those that do vary significantly in how far back they go.

Pricing and limits: Are the request limits and entity counts reasonable for what you're building? Starting on a free tier and graduating to paid as you scale is a good model when it's available.

Prediction Markets API

Prediction Markets API covers Polymarket, Kalshi, Novig, PredictIt, and Metaculus through a single endpoint. Cross-platform entity resolution is built in — the same underlying event is matched across platforms and returned under a unified market ID.

The normalized schema includes probability, volume, resolution date, platform source, and open interest. You don't need to handle schema differences between platforms or build your own matching logic.

The free Signal plan includes 2,000 entities per month with 10 requests per minute and 5-minute update frequency — enough to prototype or build a low-traffic research tool. The Edge plan ($49/month) covers 100,000 entities with sub-minute updates and all platforms. The Alpha plan ($199/month) is for higher-volume use cases: 3,000,000 entities per month at the fastest available update frequency, with full historical archive access.

Setup is fast. The quickstart guide walks through authentication and your first API call in a few minutes. REST is available on all plans.

How to choose

A few questions that help narrow it down:

How many platforms do you need? If the answer is one, go direct. If you need two or more, a unified provider saves you a significant amount of integration work.

How much infrastructure do you want to own? Writing and maintaining multiple integrations is ongoing work. Every time a platform changes its API, you're on the hook. A unified provider insulates you from that.

What are your update frequency requirements? If sub-minute freshness matters, make sure the provider supports it on your plan tier. Not all do.

Do you need historical data? If you're building for research or ML, this might be the deciding factor. Check whether the provider has it, how far back it goes, and what format it's in.

For most developers, the combination of a unified provider with a free or low-cost entry tier is the right starting point. You get coverage, normalized data, and infrastructure you don't have to build — and you can graduate to a higher plan as your usage grows.