The core test
Does the visitor mostly read content and submit one form (website), or does a logged-in user take repeated actions against persistent data over time (web application)? That single question resolves most of the ambiguity.
Signs you need a website
- You're explaining services and capturing inquiries — see [Business Website Design](/business-website-design/)
- No login or user accounts needed
- Content changes more often than logic does
Signs you need a web application
- Users log in and see different data/permissions than each other
- There's a workflow with multiple steps and persistent state
- You're replacing a spreadsheet, a portal, or a manual process — see [Internal Business Tools](/internal-business-tools/)
Why the wrong choice costs you twice
Building a web application's complexity into a website inflates cost for no reason; trying to force real user logic into a website template means rebuilding later anyway. See Web Application Development once you've confirmed which one you actually need.
Website vs Web application
Questions
Can a site be both?+
Yes — many businesses have a marketing website plus a separate, connected web application (e.g. a client portal) rather than one blended product.
Is a web application always more expensive?+
Usually yes, since it involves real user logic and persistent data — see How Much Does Custom Web Application Development Cost for the specific factors.
What if I'm not sure which I need?+
Describe the actual workflow you're trying to support — that determines the answer, not the label you'd put on it yourself.