--- url: "https://predictiontoolkit.com/tools/arbiter/" publisher: "PredictionToolkit" dateModified: "2026-11-02" --- [← Data APIs]() ![ARBITER logo]() Data API # ARBITER: Normalized Prediction-Market Data API ARBITER provides a shared data API for Polymarket and Kalshi. It combines discovery, historical prices and books, wallet analytics and cross-platform event matching with REST and WebSocket delivery. [**3.5**/ 5Editorial rating]() [Editorial assessment]() [Open ARBITER]() arbiterapi.com **Available on:** API **Pricing:** Pricing not confirmed [Screenshots]() [Explore alternatives]() [Data APIs]() [Historical data]() +1 more [Streaming data]() ## Screenshots and interface Product preview1 / 2 Introduction and sample market presentation. ## What is ARBITER? Prices are normalized to probabilities from 0 to 1 and timestamps to Unix milliseconds. Historical requests include trades, book snapshots and OHLCV candles at one-minute to daily intervals; supported at\_time reads return point-in-time prices. Use TypeScript or direct HTTP for the documented integration. Python examples appear, but the introduction still labels its Python SDK coming soon. Event matches are candidates: settlement rules and deadlines must be compatible, and historical coverage needs checking for the specific market and interval. ### Who it is for - Developers combining Polymarket and Kalshi. - Researchers comparing corresponding contracts. - Teams building historical charts or wallet analysis. ## Features and coverage - **Unified discovery** Search markets and events on both venues. - **Normalized fields** Use 0–1 prices and Unix-millisecond timestamps. - **History** Retrieve trades, books and OHLCV from one-minute to daily intervals. - **Point-in-time** Use supported at\_time queries for historical prices. - **Wallet analytics** Query positions, activity, trades and P&L. - **Cross-venue matches** Find potentially corresponding events before comparing prices. - **Live data** Stream supported trades, prices and book changes over WebSocket. ## Workflows with ARBITER ### Compare a candidate match Read both contracts' definitions and compare normalized prices. Include depth and venue fees before calculating an executable spread. ### Build a historical view Choose a market and interval and paginate trades or candles. Retrieve book snapshots when liquidity matters. ### Research a wallet Query positions and activity and link entries to their underlying markets. ## Pricing and total cost An account and API key are required. Product and introduction pages do not publish a numerical subscription price; inspect the account plan before a large ingestion job. ## Getting started **Before you start:** Python examples do not establish a released Python SDK. 1. Create an account and API key. 2. Send X-API-Key with a small market query. 3. Retain venue IDs alongside normalized IDs. 4. Choose REST history or WebSocket updates. 5. Use TypeScript SDK or direct HTTP. The introduction labels the Python SDK coming soon despite examples elsewhere; direct HTTP is a documented integration path. [Read ARBITER documentation]() ## Useful links - [Join ARBITER Discord]() ### What to check - Python examples do not establish a released Python SDK. - Matches still need compatible settlement rules and deadlines. - Check historical coverage per market and interval. A closer look ## Ratings & reviews Editorial rating **3.5**/ 5 0 user reviews PredictionToolkit editorial ### Our take on ARBITER Normalized markets, historical queries and wallet data offer useful building blocks. Public pricing and Python SDK release status need clarification for production selection. Based on documented features, setup and access terms. [How we rate]() ### User reviews 0 The main score switches to user ratings after 5 published reviews. **Be the first to share your experience** A specific example helps the next person choose the right tool. ## Related tools [Browse category]() ![Pendulum Flow public archive introduction and capture eras]() ![Pendulum Flow Orderbook Archive logo]()[Pendulum Flow Orderbook Archive]() Dataset**4.0**Editorial Inspect hourly Parquet files and coverage audits before reconstructing historical Polymarket depth. 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No. Read original rules and resolution conditions before assessing an executable trade. In this profile