Sports & Fitness — entry 023 of 34
PropLine
PropLine is a player-props odds API that aggregates lines from 12 sportsbooks plus 5 prediction-market exchanges (Kalshi, Polymarket, Matchbook, Smarkets, Novig) across 43 sports, refreshing every 60 seconds (30s in-play), and grades every prop against the final box score as won, lost, or push rather than just relaying live odds. The free tier gives 1,000 requests/day with no card required; paid Pro ($19/mo) and Streaming ($79/mo, adds webhooks) tiers raise the daily cap. A live probe of the real `api.prop-line.com` backend returned a genuine 401 ("Missing API key") confirming `auth: API Key`, with no `Access-Control-Allow-Origin` header on the response, resolving `cors: unknown -> no`.
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<a href="https://greatapis.com/api/propline/"><img src="https://greatapis.com/badge/propline.svg" alt="Scored 75 on greatapis.com"></a>Auth quickstart
- Sign up with the provider to get an API key.
- Send it on every request as a header
Authorization: <key> - The exact header isn't documented — Authorization is a common default; confirm in the provider's docs.
Your key is stored only in this browser (localStorage) and sent directly to the API — never to greatapis.