Bookmaker or betting exchange: what's the difference?

The short version

A bookmaker gives you a price, takes your stake and pays out if you win. A betting exchange puts you up against other people taking the opposite view. The platform runs the market and does the matching. The money on the other side comes mostly from other punters.

How does a fixed-odds bookmaker work?

A fixed-odds bookmaker puts a price on each outcome, takes your stake and pays the agreed winnings if your result comes in. It's the direct counterparty to your bet. Every stake it accepts adds to its exposure, and managing that is its job.

Say you stake £10 at 3.00. The bookmaker takes the £10. Your potential gross return is £30, your potential net win £20. That £20 goes into the bookmaker's overall risk. The odds are locked once your stake is confirmed, subject to the operator's rules and limits.

The whole chain fits on one line. Estimated probability → theoretical odds → margin added → displayed odds → stake accepted → risk management.

Understand how a bookmaker works →

How does a betting exchange work?

An exchange is an intermediation platform. Participants offer bets and accept them from each other. For a bet to exist, a position on one side has to meet a position on the other, at a compatible price.

The Gambling Commission draws a legal line here. A betting intermediary provides a service that lets other people make or accept bets. It isn't a party to the bet between its customers.

Stripped down, it goes like this. Someone wants to bet for a team. Someone else is happy to bet against it. The two positions get matched and the platform locks the money needed. After the result, the market settles and the platform takes whatever fees its rules set out.

"Punters are connected directly" is a handy shortcut, but only a shortcut. The platform runs the order book, the matching, the funds and the priority rules. Sometimes it uses cross-matching too. Your request can then be matched at a better price using unmatched liquidity on the other outcomes in the same market. It only does that when the price works out better for you.

Who sets the odds on an exchange?

Prices come mostly from the back and lay offers placed by participants and liquidity providers. A price is only truly available once someone agrees to take the other side at that price, or a compatible one.

On the market, some people say "I'll back this team at 2.50". Others say "I'll lay it at 2.52". The gap between the best back offer and the best lay offer works as a spread.

So you don't see one single price like you would with a bookmaker. You see several price levels, each with its own amount on offer. What you actually get depends on the side you take, how much you want, the liquidity, the timing and the platform's matching rules.

What's a back bet?

Backing means betting that something will happen. It's the bet you already know from a bookmaker. The outcome lands, you win. It doesn't, you lose your stake.

Fictional example: you back Aston Villa at 3.00 for £10. Villa win, your gross return is £30 and your gross win £20. Villa don't win, you lose £10.

The maths is short. Potential gross back win = stake × (odds − 1), so 10 × (3.00 − 1) = £20. Any commission comes after that, based on your net result on the market and the platform's rules.

What's a lay bet?

Laying means betting that something won't happen. You accept the stake of someone who has backed it. If the outcome doesn't happen, you win their stake. If it does, you pay their winnings.

Same fictional example: you lay Aston Villa at 3.00 against a £10 stake. Villa don't win, you take £10 gross. Villa win, you lose £20. What you can win is the other side's stake. What you can lose is whatever it takes to pay the backer.

People like to say the layer "plays bookie". That's true for a moment, on a single market. A layer doesn't have the tools, the spread of positions or the overall risk management of a professional bookmaker.

How do you work out lay liability?

Liability is the most you can lose on a lay if the outcome happens. It's the backer's stake multiplied by the odds minus 1.

Lay liability = stake × (lay odds − 1).

• Example 1: lay odds 3.00, stake £10 → 10 × (3.00 − 1) = £20. You can win £10 gross and you risk losing £20.
• Example 2: lay odds 1.50, stake £20 → 20 × (1.50 − 1) = £10. You can win £20 gross and you risk losing £10.

Look at the last row. The win stays capped at the other side's stake, £10. The liability climbs to £90. The higher the lay odds, the wider that gap gets. That's the thing to keep in mind before any lay position.

What is liquidity?

Liquidity is the amount available to be matched at a given price. A price can show on screen even though you can't get a big stake on at it. Only the amount displayed at that level goes through straight away.

Example: there's £20 available to back at 2.50 and £100 at 2.48. You ask to back £80 at 2.50. Only £20 gets matched at 2.50, and the other £60 sits waiting. You can then wait, cancel the rest, take a lower price or spread your stake across several levels.

In that example, the 2.50 price was only good for £20. A lovely price with almost nothing behind it can't be compared with a bookmaker price you could get a much bigger stake on. You always need to read three things together: the price, the amount available and the commission.

Matched or unmatched?

A bet is matched once someone has taken the other side of all or part of it. Until somebody accepts your price, that part stays unmatched. It isn't a done deal yet.

There are three possible states. Fully matched means the whole amount found a taker. Partially matched means only some of it did. Unmatched means nobody is there at your price.

Example: you ask for £100 at 2.50. Only £35 gets taken, and £65 waits. At this point, only the £35 is committed. A price on screen doesn't apply to your whole amount.

Margin or commission?

A bookmaker gets paid through its odds. An exchange usually charges visible fees, often worked out on your positive net result on a market.

With a bookmaker, the margin is baked into the prices. You spot it when the implied probabilities add up to more than 100%. On an exchange, you won't see the commission in the displayed odds. It usually lands after settlement, on your net winnings on the market. On Betfair Exchange, standard commission applies to net winnings on a market. Nothing is due if your net result on that market is negative. The rate depends on the account's country and the sport, and other charges can apply to some customers. These fee schedules change, so don't treat them as fixed rules.

The bit to remember: many exchanges charge commission on your net winnings on a market, under their own fee schedule, rather than on each winning bet.

Understand and calculate a bookmaker's margin →

Are odds better on an exchange?

Not necessarily. On a liquid market, an exchange's raw prices can be tighter. But you have to factor in the commission, the amount on offer and the spread between back and lay.

Here's a worked example. With a bookmaker, £100 at 2.00 gives a potential net win of £100. On an exchange, backing £100 at 2.04 gives a potential gross win of £104. With a hypothetical 5% commission on net winnings, that's £104 × 5% = £5.20. You're left with 104 − 5.20 = £98.80. The raw price was higher, yet the net win ends up lower.

As a formula, net exchange win = stake × (odds − 1) × (1 − commission rate). The equivalent net odds = 1 + [(exchange odds − 1) × (1 − commission)]. With 2.04 and 5%, you get 1 + [(2.04 − 1) × 0.95] = 1.988 ≈ 1.99.

That's still a simplified version. Commission can be worked out on the net result of the whole market rather than bet by bet. You'll sometimes read that exchange odds are "closer to the true probability". A fairer way to put it: on liquid markets, competition between participants can produce tight raw prices. How much they're worth to you then depends on commission and liquidity.

Advantages and limits of both models

The bookmaker is the simple option. Instant confirmation, and you know your potential return straight away. In return, it sets the price and its margin is harder to see. The exchange lets you back and lay, shows you prices and amounts, and puts participants in competition. But everything hangs on liquidity, your stake may only partly go through, and you have to account for commission and the spread.

Neither model wins outright. The exchange swaps the simplicity of an instantly accepted price for a more transparent market. It's also more demanding, because it lives or dies on liquidity and execution.

Are betting exchanges allowed in Great Britain?

Yes. Betting exchanges are legal and regulated in Great Britain. The UK Gambling Commission licenses them, and it classes the service as a "betting intermediary" rather than a classic bookmaker.

In Great Britain, exchanges such as Betfair operate under a betting intermediary licence from the UK Gambling Commission. The operator provides a service that lets participants make or accept bets with each other. It isn't a party to those bets itself. Elsewhere, the picture changes a lot from country to country.

Where does OddScore fit in?

OddScore mostly compares fixed-odds bookmakers, but not only. Betfair Exchange and Matchbook prices are used, alongside those of other sharp bookmakers, to work out the margin-free reference. In the UK, Betfair Exchange and Smarkets are also among the odds compared. This page explains exchanges so the structure of the market makes more sense.

OddScore pulls those odds together, strips out their margin and tracks how they move. Everything said here about exchanges is there to explain, nothing more.

Understand how OddScore compares bookmakers →

Put it into practice

Apply this guide to real odds.

Dig into the market

Odds movements are only part of the story. Here are the next topics to read.

Frequently asked questions

Sources & method