A rough test: if the main thing users do is read, it's a website. If they log in, create things, and get personalized results, it's a web app. Many products are a mix, a marketing website in front of a web app behind a login.
The distinction matters for cost and time. Web apps need a backend, a database, accounts, and far more testing, so they cost more and take longer than a comparable website. Knowing which you actually need prevents both overbuilding and underbuilding.
Updated July 2026
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