Sure bets — the data behind the phrase, without the overclaim

A sure bet exists when the prices available for every outcome of an event, taken together, imply a book that pays out more than it costs to cover — so backing all outcomes in the right proportions locks a return whichever way it lands. That can be back-vs-back across bookmakers (a three-way match-odds set, say) or a bookmaker back price against an exchange lay price. The maths is not exotic; the difficulty is that the prices have to line up *at the same moment*, across books, faster than they move. The glossary entry on sure bets sets out the definition in full.

That is the honest frame this page keeps: a sure bet is guaranteed at the snapshot it was computed, not indefinitely. OddsRelay's feed carries the arb margin as it stood when the board was computed — the docs show the field — so your product can act on a real figure while being clear-eyed that it is a snapshot, not a standing offer.

Rather than hand you raw prices and a matching problem, OddsRelay computes the sure bets over its own board and returns them finished: each opportunity with its legs — selection, bookmaker or exchange, price, bet type — an optimal stake split sized for a level return, and the snapshot-time margin. A sure bet is simply the arbitrage subset where that margin is positive, so the same GET /v2/arbitrage endpoint and its filters serve it: set minProfit to your floor, narrow by markets, bookmakers or eventIds, and toggle exchange arbs with includeExchange. The arbitrage betting API spoke covers the scanner-builder view in depth.

Coverage is what makes sure bets appear at all. The board spans 60+ UK bookmakers with bet365 included as standard, and the opposing side is priced from Betfair, Smarkets and Matchbook — so a genuine gap at a book a shallow feed skips is still one your product can show. The coverage dashboard lists the books and their freshness before you commit.

A sure bet needs an opposing side to cover the other outcomes, so it is honest only where that side exists. The feed surfaces exchange-based sure bets across UK and Ireland today — the markets with the exchange liquidity a lay side depends on. Where a market has no in-region exchange, we don't manufacture one: the honest structure there is back-vs-back dutching across bookmakers, and the regions view says which markets are which. We never imply a lay-based sure bet in a market that has no exchange.

That gate is deliberate. It is why the sure bets you see are ones a product could actually attempt, in markets where the covering side is real — not a longer list padded with opportunities that can't be completed.

Genuine sure bets are rare, small and short-lived — and any vendor who tells you otherwise is selling the word, not the data. Bookmakers move, exchanges rebalance, limits and stake caps bite, and the margin that existed at the snapshot often isn't there at execution. That is why every opportunity is labelled with its snapshot-time margin and never a guarantee, and why we've written up why surebets disappear in full. A good feed improves your odds of catching the real ones; it does not make returns certain.

Two more limits up front: the feed is pre-match on a ~3s polling cycle, not in-play; and full cross-book arb across all 60+ books at once, streaming delivery, historical archives and middles are on the roadmap, described as coming rather than shipped. The arbitrage use-case shows how builders wire the opportunities in, and a free trial key points your product at the live endpoint this week.