Risk warning. CFDs and leveraged FX carry a high risk of rapid loss; a majority of retail investor accounts lose money. General information, not financial advice.
Every broker comparison in the world leads with spread, because spread is a number you can put on a landing page and it is comparable across firms.
It is also, for most active traders, not the largest cost. The largest cost is the difference between the price you clicked and the price you got — and no broker advertises that, because it is not a single number and it looks worst exactly when it matters most.
What slippage actually is
When you send a market order, the price can move between your click and the fill. If it moves against you, that is negative slippage; if it moves in your favour — which does happen at brokers with symmetric execution — that is positive slippage.
Small amounts are normal and unavoidable: markets move. What separates brokers is the distribution, and specifically two things.
Is the slippage symmetric? A broker that passes on positive slippage as well as negative is behaving differently from one where the surprises are always in one direction. Over a few hundred trades this is measurable, and it is the single most revealing statistic about a venue.
What happens under stress? Every broker looks fine on a quiet Tuesday. The number that matters is the fill during a data release, at a session open, or when a position gaps.
Advertised spread is a claim about the calmest moment of the day. Slippage is what you pay in the moments that decide your month.
Put a number on it
Hand-waving about "hidden costs" is easy. The arithmetic is better, and it only needs one fact you can verify yourself: on a pair quoted to four decimal places against the US dollar, one pip on a standard lot is $10, because a pip is 0.0001 and a standard lot is 100,000 units.
So a cost per round turn looks like this:
Total = 10 x (typical spread in pips) + (commission both sides) + 10 x (average adverse slippage in pips)
Now notice what that third term does. Half a pip of average adverse slippage adds $5 per standard lot round turn — silently, on every trade, forever. Against two brokers whose advertised spreads differ by two tenths of a pip, that is a difference an order of magnitude larger than the one you were comparing.
And it compounds against strategy type rather than against volume. On a trade targeting 100 pips, half a pip of slippage is half a percent of the gross move and effectively noise. On a trade targeting 5 pips, the same half pip is ten percent of the entire edge, taken before the position has done anything.
That is the whole reason execution deserves its own analysis: it is not a small version of the spread problem, it is a differently shaped problem that lands hardest on exactly the traders who shopped hardest on spread.
Why "0.0 pip spreads" is an incomplete sentence
Raw-spread accounts genuinely offer very tight spreads — and charge a commission per lot. That is a legitimate and often cheaper structure, but the comparison to a "commission-free" account requires adding the commission back in.
The honest comparison is all-in cost per round turn:
| Account type | Spread | Commission | Where the cost hides |
|---|---|---|---|
| Standard / commission-free | Wider, marked up | None | Inside the spread — and it can widen when you need it not to |
| Raw / ECN | Very tight | Per lot, both sides | Nowhere — but check it against your average trade size |
| Fixed spread | Fixed in normal conditions | Usually none | In the "normal conditions" clause; fixed spreads can widen or requote |
Our fuller treatment is in spread vs commission, lowest spread forex accounts, raw spread vs standard account, when is it cheaper and ECN vs market maker brokers.
The overnight cost nobody budgets for
If you hold positions for days, swap is frequently your largest single cost, and it is asymmetric by direction — one side of a pair can pay you while the other charges heavily.
A strategy that looks profitable on entry and exit prices can be a loss-maker once four nights of swap are added, and there is a triple-swap night each week to account for the weekend. Cost it before you trade it, not after. Detail in forex swap and rollover fees explained.
What the rules require, and what they leave to the firm
Execution sits partly inside regulation and partly outside it, and the boundary is worth knowing before you complain to the wrong body.
Inside: firms owe retail clients a best-execution obligation under MiFID II and must publish an order execution policy describing how orders are handled and routed. The EU and UK retail regimes also fix the surrounding protections. ESMA's product intervention of 27 March 2018 capped retail leverage from 30:1 on major currency pairs down to 2:1 on cryptocurrencies, introduced a margin close-out at 50% of minimum required margin, and required negative balance protection per account. The FCA made equivalent rules permanent from 1 August 2019, requiring firms to limit leverage between 30:1 and 2:1, close out at 50% of required margin, and guarantee a client cannot lose more than the total funds in the account.
Outside: the actual distribution of your fills. There is no requirement to publish average slippage per instrument in a form a retail client can compare across firms, which is precisely why you have to generate the data yourself.
Note the interaction, because it catches people. Negative balance protection does not stop a gap costing you the account — it stops it costing you more than the account. And the close-out rule fires "as soon as market conditions allow", which in a gap means after the gap, not at the 50% level.
Measure it yourself — the only reliable method
Nobody will hand you this data. Fortunately it takes about two weeks to generate.
Most platforms export order history that contains everything you need. Two weeks of honest logging tells you more about a broker than any review — including ours.
What good execution looks like structurally
Not a guarantee of fills, but the conditions that make good fills likely:
- Top-tier regulation, which brings best-execution obligations. See what FCA regulation means and ESMA rules explained.
- A published execution policy you can actually read, including how orders are routed.
- Symmetric slippage as a stated policy, not just a marketing line.
- A platform with real order types — MetaTrader 4 vs 5, MT5 vs cTrader.
- Server locations and latency that match where you trade from, which matters more for short holds than most people expect.
Brokers we cover and where to read the detail: Pepperstone (review), AvaTrade (review, fees and spreads), Eightcap, and comparisons in Pepperstone vs IC Markets and Pepperstone vs Eightcap.
The counter-argument
Two objections deserve a hearing, because taken too far this analysis becomes its own trap.
Slippage is not evidence of bad faith. Markets move; liquidity thins; a fill worse than the click during a payrolls release is physics, not misconduct. A trader who interprets every adverse fill as being cheated will churn through brokers permanently and never build the sample size that would tell them anything. The finding is a one-sided distribution over hundreds of trades, not a bad fill you remember.
And for most people this is not the binding constraint. If you place a few trades a month with wide targets, half a pip of slippage is irrelevant next to whether you sized the position correctly. The traders for whom execution is decisive are the ones with short holding periods and high trade counts — and they are also the population with the lowest survival rate, which is worth sitting with. Optimising execution for a strategy that has no edge is polishing the wrong thing.
The honest hierarchy is: regulation and getting your money back out first, position sizing second, all-in cost third, execution quality within that. This page is about the third and fourth items, and they only matter once the first two are settled — see how to choose a forex broker and forex broker red flags.
The scalper's special case
If you trade very short holding periods, execution is not one factor among several — it is the entire business. A strategy with a two-pip target cannot survive one pip of average adverse slippage, no matter how good the entry logic is.
That is why best brokers for scalping is a different list from best brokers generally, and why scalpers should measure before committing size rather than after.
Frequently asked
What is slippage in forex?
The difference between the price you requested and the price your order filled at. It can be negative or positive, and the distribution across a few hundred trades tells you far more about a broker than any advertised spread.
Is slippage a sign of a bad broker?
Not on its own — markets move, and some slippage is unavoidable. Consistently one-sided slippage, or extreme slippage during ordinary conditions, is the warning sign.
How do I compare brokers on real cost?
All-in cost per round turn: spread plus commission plus measured average slippage, plus swap if you hold overnight. Log your own fills for two weeks; it is the only data that reflects your instruments, size and hours.
Written with AI assistance and reviewed by the NorwegianSpark SA editorial team. NorwegianSpark SA, org. 834 984 172. Some links are affiliate links; see our disclosure. Trading involves substantial risk of loss.
Sources
- ESMA — agreement to prohibit binary options and restrict CFDs for retail investors, 27 March 2018 (leverage caps, 50% margin close-out, negative balance protection): esma.europa.eu
- FCA — permanent restrictions on the sale of CFDs and CFD-like options to retail consumers, in force 1 August 2019: fca.org.uk
- EU — Directive 2014/65/EU (MiFID II), best execution obligations: eur-lex.europa.eu
