What the order book shows
The book displays buy bids and sell offers grouped by price and quantity. The best ask is the first price at which you can buy at that moment; the best bid is the first at which you can sell. The difference is the market spread. Neither price represents an unlimited quantity.
A chart generally shows completed trades. If the book changes before your order arrives, execution may use other levels. Look at depth and order size, particularly in thin markets, instead of calculating everything from the prominent last price beside the chart.
Market orders and the average execution price
A market buy consumes available sell offers until the quantity is filled or the platform’s protection conditions intervene. It does not set one execution price in advance. The average combines the individual fills, with fees added or deducted according to the product rules.
For a hypothetical 0.006 BTC purchase, suppose 0.002 BTC is offered at €60,000 and another 0.004 at €60,100. The cost before fees is €120 + €240.40 = €360.40. The average is about €60,066.67 per BTC, although the first offer you saw was €60,000.
Limit orders control price, not the outcome
A buy limit at €59,900 should not execute above that price; a sell limit at €60,200 should not execute below it. Without a matching counterparty the order can remain open. It neither reserves a future price nor promises the market will reach your level.
A buying limit above the best available offers may execute immediately against them. You need not pay the maximum limit: fills can occur at better prices within it. Because it matches existing orders, that limit order may be a taker rather than a maker.
Partial fills and cancellations
Suppose a 0.006 BTC limit order fills only 0.002. Another 0.004 remains pending unless the time-in-force instruction says otherwise. Order history describes the whole instruction; trade history records each fill. Check both before deciding how much you still need.
Cancellation removes the unfilled portion if it arrives in time. It does not reverse earlier purchases. Submitting another order for the original quantity without checking fills may buy more than intended. An open order can keep funds reserved until it finishes or is cancelled.
Maker, taker and post-only
Makers add liquidity to the book; takers consume existing liquidity. Many schedules distinguish their charges, but some do not. Bybit EU publishes one starting spot fee, whereas other schedules have separate columns. Compare the product in the Bybit review and spot pricing models.
Where offered, post-only requests that an order rest on the book. If it would match immediately, the system can cancel it rather than execute it as taker. This controls execution mode, not the certainty of a purchase or a lower fee under a schedule charging both sides equally.
Time in force is part of the instruction
A limit order may persist until cancellation, or execute what is immediately available and cancel the remainder. Other instructions require the full quantity to fill at once. Platforms may label these GTC, IOC or FOK; read the explanation before changing the default.
Not every order type exists in every product. A persistent limit for a non-urgent purchase serves a different purpose from an order cancelling any unfilled remainder immediately. Also check whether the input is euros or asset units and whether fees use part of the reserved balance.
Stops activate orders without always fixing the fill price
A stop normally uses a trigger price to activate another order. A stop-market order can execute beyond its trigger during a fast move. A stop-limit adds a price boundary but may remain unfilled if the market jumps past it. Neither is price insurance.
Futures introduce settings such as the trigger reference price and reduce-only instructions. Do not automatically transfer assumptions from a spot screen. See spot versus futures for context; for a first euro-funded BTC purchase, focus on the actual spot instruction you intend to submit.
Choose for the particular transaction
Before submission, ask whether you need execution now, what maximum or minimum price you accept, and what you will do with a partial fill. A market order can suit the first priority; a limit can express the second. Neither prevents losses from later price changes.
Review pair, side, unit, quantity, limit and time in force. Afterwards inspect the result and available balance. Continue with buying Bitcoin with euros for the full purchase process, or Bitvavo versus Bybit when comparing platforms rather than inferring cost solely from the order’s name.
