Most Common Bugs Found During Manual Testing

If you’ve spent any time in software testing, you know this already: manual testers are the last line of defense before users hit an application. It’s not glamorous, but it’s necessary. The bugs that manual testing catches often live in the edges—the awkward, unautomated corners of a user experience where logic, design, and real-world behavior don’t align.

This guide isn’t about fluff. We’re not listing every hypothetical issue you might ever see. We’re focusing on the real, repeat offenders—the bugs manual testers keep finding across industries. And we’ll talk about what they look like in action, why they matter, and how Uncodemy trains you to spot them early.

Most Common Bugs Found During Manual Testing

Mr. Rishiraj / 1 week
0
9 min read

MVC-Architecture

By the end, you'll know exactly what to watch out for—and how to build a career doing it.

1. UI Bugs: Where Visuals Go Wrong

You don’t need to be a designer to spot a broken layout. But you do need an eye for detail. Here are the usual suspects:

Misaligned buttons, text, or fields
Elements that disappear on smaller screens
Font inconsistencies

Uncodemy’s manual testing training puts you in front of actual interfaces—bad ones and good ones—so you can learn to spot the difference fast.

2. Navigation Bugs: When Users Get Lost

Good navigation is invisible. When it breaks, users notice immediately.

Dead links
Breadcrumbs not updating
Menus that collapse without opening

Uncodemy walks you through real-life testing flows where you document these issues with clear repro steps and evidence.

3. Form Bugs: Small Inputs, Big Problems

Forms are simple in theory and messy in practice. Users enter unpredictable data. Bad forms break fast.

Fields that don’t validate correctly
Mandatory fields not marked
Submit button doesn’t trigger anything

You’ll spend a lot of time on forms in Uncodemy’s course. Not just spotting issues, but learning to write proper bug reports that devs actually use.

4. Functionality Bugs: The Core Stuff

These bugs affect the actual features users depend on. They’re often the most critical.

Buttons trigger the wrong action
Filters and search not working properly
Pagination bugs

At Uncodemy, you’ll test full features—ecommerce carts, booking forms, dashboards—and learn how to check edge cases most testers miss.

5. Compatibility Bugs: Devices and Browsers Don’t Agree

This one never goes away. Manual testers still find cross-browser issues all the time.

CSS not rendering the same way in Chrome vs. Firefox
iOS vs Android inconsistencies
Zoom issues

Uncodemy includes compatibility labs where you simulate these environments and spot layout and logic issues across real devices.

6. Error Message Bugs: No Info, Bad Info

When something fails, users need to know what happened. These bugs make that impossible.

Missing error messages
Wrong message shown
No way to recover

You’ll test broken states deliberately in Uncodemy’s manual testing projects. That’s where real skill shows up.

7. Data Bugs: When Input Meets Backend

Even basic inputs can break things if they’re not handled properly.

Data not saving
Wrong data shown
Partial updates

You’ll learn how to trace bugs like these by checking before/after states, expected outcomes, and UI vs database mismatches.

8. Performance Bugs: Slow is a Bug Too

Performance issues don’t always crash apps—but they kill user satisfaction.

Pages that load too slowly
Laggy buttons
Timeout errors

Uncodemy teaches you to run basic performance testing alongside manual checks, even using lightweight tools or browser dev tools.

9. Session and State Bugs: The Invisible Glitches

These bugs are subtle. But they lead to chaos if left unchecked.

User sessions not handled correctly
Multiple tabs desync
Caching bugs

You’ll dig into these in Uncodemy’s session management modules where state handling is tested under real workflows.

10. Usability Bugs: Not Technical, Still Critical

Even if everything works, that doesn’t mean it makes sense.

Unclear buttons or actions
Poor feedback
Inconsistent UI behavior

You’ll learn how to test from a user’s perspective, not just a tester’s. That’s a key skill that Uncodemy builds with its real-app testing exercises.

11. Content Bugs: The Ones Everyone Misses

Words matter. Content errors are some of the most overlooked bugs.

Typos and grammar mistakes
Incorrect labels or instructions
Placeholders still live

Uncodemy’s UI review templates include content QA so you catch these before launch.

12. Accessibility Bugs: Real Users Need This

Testing for accessibility is not optional.

Missing alt text for images
Forms that can’t be filled with a keyboard
Poor color contrast

Uncodemy’s course modules touch on accessibility as part of UI and compliance testing—because it matters, and it’s often ignored.

So Why Are These Bugs Still Around in 2025?

Because software is always changing. New features break old ones. Developers are on deadlines. Automations don’t catch human behavior issues. And that’s where manual testers prove their value.

With Uncodemy, you’re not just learning how to click around. You’re learning to think like a user, test like a professional, and report like someone the dev team listens to.

Every bug in this list is one you’ll encounter in practice. And through Uncodemy’s hands-on manual testing course, you’ll not only spot these—you’ll learn how to: