Show up, get stamped, walk in. That is the ad for a visa on arrival countries list. The reality has rules, and the rules vary by destination and by passport. Knowing the difference between visa on arrival available and visa on arrival easy is the whole game.
First, the fee. Visa on arrival is rarely free, and the amount depends on your destination and nationality. You will usually pay cash, in dollars or local currency, at a dedicated counter before immigration. The card machines at those counters are unreliable at best. Bring the cash. This is the single most common way a visa-on-arrival trip goes sideways.
Second, stay limits. Some destinations give you 30 days, some 90, some less than you would guess. A few let you extend. Most do not advertise it. How long you can stay matters as much as whether you can get in, and the honest lists track both.
Third, the queue tax. E-visa travelers walk past you. Visa-on-arrival lines at busy airports can eat an hour or more, and they move slowest exactly when your connection is tight. If a destination offers both options, the e-visa is usually the better hour of your life.
The shortcut nobody regrets: do the trip visa check app download before you pack. A decent can I go travel visa app tells you the fee, the stay limit, and the document list in about thirty seconds, which is more than most blog lists manage in thirty paragraphs. Use it as a pre-flight checklist, not your only source. And when the trip actually matters, run a "can I travel without a visa checker" search against your real passport and dates, because the counter answer and the blog answer are not always the same.
None of this is a reason to avoid visa on arrival. It is a reason to arrive prepared: cash, photos, return ticket, hotel booking, and the right expectations. Check your passport and destination in the visadocs.fyi database, and grab the instant eligibility report for the full breakdown.