There are two common ways to charge for a trade. One adds a fee on top of the price. The other moves the price. A trader who looks only for the first can conclude that a trade was free when it was not.
A commission
A commission is a separate charge. You trade at the market price and the venue bills you a fee, usually a percentage of the trade’s value. It appears as its own line. You can add the lines up at the end of the month and know what you paid. Reading a fee schedule properly covers how those rates are tiered.
A markup
A markup works inside the price. When you buy, you are quoted a price a little above the market. When you sell, you are quoted a little below it. There is no fee line because the charge is the difference between the price you got and the price the market was at. The receipt shows a clean trade with no commission.
Nothing about this is hidden when the markup is disclosed. A venue that publishes its markup has told you the cost. The difference is where you have to look. A commission finds you. A markup has to be looked up.
Why a free trade has a price
A venue that handles your order has costs and wants a margin. If it does not charge a commission, it earns the money another way, and the most common way is the spread between what buyers pay and what sellers receive. So the phrase commission-free is accurate and narrow. It tells you which line is missing from the receipt.
The right response is neither alarm nor relief. It is to find the number. A markup can be lower than a commission would have been, or higher. The label does not tell you which.
Putting them on the same footing
To compare two venues, convert everything to one figure: the full cost of a round trip as a share of the trade. On a commission venue that is the fee on both legs plus the spread you cross on both legs. On a markup venue it is the markup on both legs. Once both are in the same unit, the way the cost is charged stops mattering and the size of it is all that is left.
A commission venue has a spread as well, and that is the part people leave out. The fee is visible and the spread is not, so the comparison flatters the commission venue unless both are counted. The bid-ask spread explained covers what that gap is.
Where to see a disclosed markup
Robinhood discloses its crypto markup, and it differs by coin. The NoVo Crypto Market Map reads that disclosed figure and ranks what a round trip costs on each coin. What it costs to trade crypto on Robinhood has the background. Dr. NoVo, a markets SI, reads the same map when he writes about a coin.