"It works for me." It's the most natural thing to say, and the most expensive assumption in web development. Your site working for you tells you almost nothing about whether it works for your customers.
Why you're the wrong test case
- You're logged in. Customers aren't. Login state changes what loads and how.
- Your browser has your data cached. A first-time visitor loads everything fresh — and slower.
- You know where everything is. You navigate on autopilot. Strangers get lost where you never would.
- You're on your device, your network. Customers are on old phones, weak signals, different browsers.
- You skip your own checkout. So you never feel the friction a buyer feels.
The gap this creates
Every one of those differences hides problems from you. The broken thing works for you because you approach it the way it was built to be approached. Real people don't, and that's exactly where sites fail.
How to see what customers see
- Test in a private/incognito window, logged out
- Use a different device and a slower network
- Ask someone unfamiliar to complete a task and watch where they stumble
- Actually go through your own checkout as a stranger would
The honest fix
The most reliable way past "it works for me" is a genuinely independent check — someone with no memory of how the site is "supposed" to work, testing it the way a customer actually would. That fresh, outside perspective is the whole point of a QA audit, and it catches what you literally cannot see from the inside.