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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallThe right alternative depends on what your bot needs to do. Kalshi is the clearest documented venue-level option here, with market data and account functions; Prediction.com and Adjacent offer cross-venue data services for research and comparison. Do not assume a data API that covers multiple venues can also place trades on them.
Which Polymarket API alternative fits your bot?
Start by separating APIs for a specific trading venue from services that bring data from multiple venues into one interface. Venue APIs may expose account functions and trading capabilities; data-layer APIs can simplify discovery and comparison without necessarily supporting execution.
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| Option | Best fit | Documented capabilities | Verify before choosing |
|---|---|---|---|
| Polymarket API | A bot designed for Polymarket markets | Polymarket’s Help Center points developers to documentation for market discovery, resolution and trading, and describes linked code as open source and free to use. | Check the live docs for endpoint-specific authentication, rate limits, supported SDK versions and trading requirements. |
| Kalshi API | A bot that can trade or monitor Kalshi markets | Kalshi describes REST access to public market data and order books, plus a member’s own orders, trades, portfolio and portfolio history. | Check membership and account eligibility, current limits and the restrictions in Kalshi’s Developer Agreement. |
| Prediction.com API | Cross-venue discovery, normalized data, historical research or market comparison | Documentation covers prices, trades, historical data, matched markets and order books, with endpoints for markets, events, matching markets, order books, trades and price history. | Confirm coverage for the specific market, data freshness and historical depth, quotas, price and whether execution is offered. |
| Adjacent API | Kalshi and Polymarket data research, reference rates, news and filing context, or agent workflows | Documentation describes market data, indices, reference rates, news, filings and an MCP option. Anonymous public data is delayed by 15 minutes; real-time endpoints require authentication. | Check endpoint scopes, latency, history, plan limits and whether your intended use is permitted by the service’s terms. |
Polymarket’s own Help Center is the starting point if the bot will remain on Polymarket. The other services are alternatives for different needs, not interchangeable replacements.
Can you build a prediction market bot with Kalshi’s API?
Kalshi documents a REST API with public market data and order books, as well as a member’s own orders, trades, portfolio and portfolio history. Its Help Center says the API provides access to those account details along with all markets’ order books and a limited number of statistics. See the Kalshi API documentation.
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That makes Kalshi a documented venue-level alternative for a bot that monitors or trades Kalshi markets. It does not establish that you can use the API without a qualifying account, or that every bot use is allowed. Review the current Developer Agreement, membership requirements and API limits before implementation.
Is there one API for Polymarket and Kalshi?
Prediction.com and Adjacent document data services that cover multiple venues, but their reviewed documentation does not establish a unified trading-execution interface. A service may help a bot find or compare markets across venues while leaving order placement to each venue’s own API.
Prediction.com documents normalized prices, trades, historical data, market matching and order-book endpoints. Adjacent documents Kalshi and Polymarket market data alongside indices, reference rates, news, filings and an MCP option. Adjacent’s anonymous public tier is delayed by 15 minutes; real-time endpoints require authentication. Check current documentation for precise coverage and access conditions.
How to compare APIs for a bot
Before choosing, map the data and permissions your strategy actually requires. Coverage alone does not tell you whether an API can support your bot’s execution path or backtests.
- Purpose: Identify whether the API provides market data, account information, order submission, or a combination. Do not infer execution support from market-data coverage.
- Market matching: Verify that two apparently similar markets share the same outcome, close time and settlement definition. Similar titles are not enough. Prediction.com’s examples show that venues can use different identifiers, price formats and settlement descriptions.
- Data requirements: Check for the specific order-book snapshots or streams, trades, historical data, resolved outcomes and market metadata your bot needs. Confirm update frequency and historical depth rather than assuming they are uniform.
- Operations: Review authentication, quotas, rate limits, errors and reconnect behavior in current documentation. Kalshi says its rate limits can change. Adjacent distinguishes delayed public data from authenticated real-time endpoints.
- Permissions and handling: Read applicable agreements before caching, aggregating, redistributing or using data for users beyond the member’s own trading.
What Kalshi’s API terms mean for bot builders
Kalshi’s Developer Agreement limits API use to facilitating a member’s own trading and restricts collecting, storing or sharing API data outside that purpose without prior written authorization. A bot that aggregates data for others or redistributes it may therefore raise a different permissions question from a bot used for a member’s own trading. Read the current agreement and get written authorization where required before building around broader data use.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What to verify before deployment
API endpoints, venue coverage, terms, authentication, quotas and service plans can change. Confirm the live docs and agreements for the specific markets and workflows you intend to use. The documented capabilities described here are not evidence of measured execution latency or bot profitability.
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