PropLine is a real-time sports betting odds API covering 110+ books and 70+ sports and leagues: US sportsbooks (DraftKings, FanDuel, BetMGM, Fanatics, Hard Rock, BetRivers), Pinnacle, DFS sites (PrizePicks, Underdog, Sleeper), prediction markets (Kalshi, Polymarket) and exchanges (Betfair, Smarkets, Novig, ProphetX). Every player prop is graded against the official box score: each Over/Under ships with won/lost/push/void plus the real stat. Five books stream in real time (about one second per line move). Pricing is per request, not per credit, and the response format is the-odds-api compatible, so switching is a base-URL change. Free tier: 1,000 requests/day, no card. Hobby $9/mo (5,000/day) unlocks every analytics feature: graded results, cross-book +EV, line history and opening/closing lines. Pro $19/mo (25,000/day) adds CSV exports; Streaming Lite $39/mo (250,000/day) and Streaming $79/mo (1M/day) add webhooks and a websocket. Python, Node, MCP and CLI SDKs. Built for sports betting developers, quant bettors, DFS tools, bet trackers and odds-comparison apps, and AI agents (a hosted MCP server and llms.txt are available at prop-line.com).