Tipping norms travel badly. People arriving from the United States in particular over-tip out of habit while still worrying they have under-tipped, and the pin terminal (card machine) prompting for a percentage before the payment goes through has made the question feel more pressing than it used to be.
No obligation — staff wages already factor service into the price, unlike the US system where tips subsidize below-minimum base pay. That said, a small tip for good service is a normal, appreciated gesture rather than an eccentric one. The common approach is rounding up the bill to a round number for a quick lunch or drinks, and something like 5–10% for a proper sit-down meal with good service — so on a €50 dinner, an extra €2.50 to €5 reads as generous rather than obligatory. Cash left on the table or handed over when paying is more common than adding it to a card payment, though most places let you add a tip on the pin terminal now too. That last part is actually a live irritation for a lot of people here: pin machines increasingly prompt a tip percentage before you can decline, and there's real pushback in Dutch consumer media against that creeping expectation, especially at counters and fast-casual spots where tipping was never really the norm. Selecting "geen fooi" (no tip) is completely acceptable and nobody will treat you differently for it.