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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.
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, low-spread forex brokers 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. Cost it before you trade it, not after. Detail in forex swap and rollover fees explained.
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 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.
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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](/disclosure). Trading involves substantial risk of loss.
Sources
- ESMA — MiFID II best execution requirements for investment firms: esma.europa.eu
- FCA — Best execution and order handling: fca.org.uk
- EU — Directive 2014/65/EU (MiFID II), best execution obligations: eur-lex.europa.eu