A swap-free (or Islamic) account holds positions overnight without paying or receiving the interest-rate differential, so it complies with the prohibition on riba.
The cost usually reappears elsewhere. Brokers commonly widen the spread, charge a fixed administration fee per lot after a grace period of a few days, or restrict which instruments qualify — exotic pairs and metals are often excluded. Compare the total cost of a multi-day position on both account types before assuming swap-free is cheaper; for short-term trading it frequently is not.
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Account Types, and What Actually Changes Between Them
Standard, raw, cent, swap-free, professional. What genuinely differs between the tiers, and the one reclassification that costs you protections.