Ergast F1
F1 data from the beginning of the world championships in 1950

Real-time FanDuel Sportsbook odds — live & in-play and pre-match, with a keyless public snapshot.
FanLine Wire API is a free Sports & Fitness API that requires no API key, is served over HTTPS and supports CORS, so it can be called from the browser.
FanLine Wire API reference: FanDuel odds for every sport, plus full NFL, NCAAF, NBA and NCAAB boards (halves, quarters, team totals, player props) in New Jersey and Kansas, over REST and a filtered WebSocket stream, with bet-slip links.
Details from fanlinewire.com.

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F1 data from the beginning of the world championships in 1950
MLB since 2015 plus college baseball: pitches, plate appearances, box scores and sportsbook odds
NBA, WNBA and college basketball: play-by-play, shot locations, box scores and sportsbook odds
The FanLine Wire API is provided by FanLine Wire (fanlinewire.com). FanLine Wire API reference: FanDuel odds for every sport, plus full NFL, NCAAF, NBA and NCAAB boards (halves, quarters, team totals, player props) in New Jersey and Kansas, over REST and a filtered WebSocket stream, with bet-slip links.
Yes. The FanLine Wire API is listed in the Sports & Fitness category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The FanLine Wire API requires no authentication, so you can start making requests without signing up.
Yes. The FanLine Wire API supports CORS, so front-end JavaScript can call it directly.
Yes. The FanLine Wire API is served over HTTPS, so it's safe to use in production.