You press buy at one price and receive a confirmation at another. That difference is not automatically an error or a hidden fee. You may have crossed the spread, consumed several levels of available liquidity, or submitted an order while prices were changing. To understand the result, start with the price you expected and identify exactly what that number represented.

The useful question is not simply whether an asset looks liquid. It is whether your chosen market can absorb your particular order, at an acceptable price, when you submit it.

The displayed price needs a label

On an order book, the best bid is the highest available buying price and the best ask is the lowest available selling price. Their difference is the spread. Kraken's trading glossary uses these definitions and distinguishes them from the last completed trade.

If you buy immediately, you normally match with sellers on the ask side. If you sell immediately, you normally match with buyers on the bid side. A large number in an app might instead show the last trade, a midpoint or an indicative quote. None tells you, on its own, what your entire order will cost.

Before comparing two venues, check that you are comparing the same asset pair, order size and kind of quote. A narrow spread against one currency says little about a different pair. Save the order preview if you want to review execution later, because a refreshed screen is a different observation.

Spread, slippage and fees answer different questions

The spread describes the gap between the two sides of the market. Slippage compares your actual execution with a specified expectation. A trading fee is a separate charge under the platform's pricing rules. Combining all three without identifying the benchmark can count the same cost twice.

Consider a hypothetical order book with a £99 bid and a £100 ask. One unit is offered at £100 and two more at £101. Buying all three consumes £302 of liquidity, giving an average execution price of approximately £100.6667.

Using the initial £100 ask as the benchmark, slippage is £2 across the order. An assumed fee of 0.25% adds £0.755, rounded to £0.76, for a total debit of £302.76. The £1 spread is not another charge to add to that total.

Against the £99.50 midpoint, the execution shortfall is instead £3.50 before fees. The trade has not changed; the comparison has. Keep your benchmark consistent when comparing trades or evaluating an automated strategy.

Depth matters more than a busy-looking market

Trading volume records completed activity over a period. Depth describes orders available at different prices now. Kraken's market-data documentation also warns that a visible feed does not necessarily reveal hidden quantities or every pending instruction.

For your decision, inspect the amount available near the current price, not just the headline volume. The three-unit example had a small quantity at the best ask. Its displayed price was achievable for one unit, not for the whole purchase.

Imagine repeating that order after the first seller cancels. Even if yesterday's trading volume is unchanged, your expected fill is different. Treat the book as a snapshot rather than a reservation of liquidity.

Splitting an order deserves the same scrutiny. Smaller pieces may meet different available quantities, but later pieces face later prices and potentially additional charges. Compare the full proposed execution, including the time between pieces, instead of assuming that smaller automatically means cheaper.

Choose which uncertainty you can accept

The SEC's Trading Basics explains the central distinction: market orders prioritise execution, while limit orders set an acceptable price. Its guidance concerns securities, but the distinction is useful when reading a crypto venue's own order rules.

A buy limit sets the most you will pay per unit; a sell limit sets the least you will accept. That control does not promise a completed trade. Available quantity, queue priority and your instructions still matter. An order can fill partly and leave the remainder waiting.

Read the time-in-force setting before submission. Depending on the venue, instructions may cancel an unfilled remainder immediately or leave it working. Market-price protections can also interrupt execution. Do not assume that every platform handles an unfinished order identically.

For a planned purchase, a missed fill may be acceptable. For an urgent exit, waiting may carry a different consequence. Write down which outcome matters most before selecting the order type, rather than changing it impulsively when the confirmation differs from your expectation.

Stops and decentralised swaps need separate checks

A stop price is a trigger. It is not necessarily the price at which you leave the market. FINRA's guidance explains that a triggered stop-market order can fill beyond the trigger, while a stop-limit order can remain unfilled. Crypto products may also use different trigger references, so check whether yours follows a last trade, index or mark price.

Ask the platform to explain the sequence in ordinary language: what activates the instruction, what order appears next, and what happens if there is insufficient liquidity? Those questions expose the practical difference between a planned exit and a guaranteed one.

Do not transfer the whole order-book explanation to every decentralised swap. Uniswap's documentation describes pool-based execution, while other mechanisms may use different arrangements. For a swap, inspect its quoted output, price impact, slippage tolerance and network charge. A tolerance setting is an execution condition, not a prediction that the final outcome will be favourable.

Review the complete order before confirming

Use the preview to answer a short sequence of concrete questions:

  • Which pair, venue and product am I using?
  • What does the displayed price represent?
  • How much quantity is available near it?
  • What average price and total debit does the preview estimate?
  • Which fees are separate, and which costs are already reflected in the quote?
  • Can the order fill partly, remain open or be cancelled?
  • Which benchmark will I use to assess the result?

Afterwards, compare the execution record with that preview. Record quantities, fills and fees separately. If an automated strategy repeatedly receives materially different prices from those assumed in testing, investigate the execution assumptions before increasing its size. A clean record lets you distinguish a price movement from a pricing misunderstanding.

Crypto trading can lose the entire amount you commit.