As a UI testing guru with over a decade of experience spanning thousands of devices, I‘ve seen the impact firsthand that UI bugs can have on a product. One single bug that slips into production can damage your brand, frustrate users, and require major engineering resources to fix – not to mention app store reviews calling out problems for all to see.
My goal in this guide is to share the most frequent categories of UI bugs I encounter to help your team prevent these issues from ever seeing the light of day. Consider this your field guide to seeking out and destroying the top 10 most wanted bugs in UI testing.
Why UI Bugs Matter
Before we dig into the bugs themselves, it‘s important to level-set on why squashing these pesky UI defects matters. Here are some statistics around the hard costs bugs can inflict:
- 86% of users will uninstall a buggy mobile app after only 2-3 uses (Anlyz)
- A single hour of downtime due to bugs costs on average $100,000 for web-based companies (Gartner)
- Companies lose an average of $1.25M annually due to software failures and bugs (Cambridge)
Beyond angry users and lost revenue, UI bugs also divert precious engineering time away from building new features to instead firefight quality issues. Letting UI bugs escape into production sets off the law of diminishing returns, taking time, energy and money to resolve.
In other words – bad UI bugs are extremely costly on multiple fronts.
With those cheerily statistics in mind, let‘s cover what I‘ve found to be the 10 most frequent categories of UI bugs plaguing testing teams.
1. Cross-Browser Compatibility Bugs
Supporting browsers consistently should be priority number one for developers. After all, your beautifully polished UI means nothing if a chunk of users can‘t even access your app properly.
Here are some of the cross-browser issues I frequently encounter:
- Layouts rendering differently across browsers
- Images or icons failing to load
- Javascript functionality crashing on non-Chrome browsers
- Safari and Firefox users receiving mobile layout on desktop
- Browser-specific CSS prefix missing causing styling failure
To prevent users from encountoning a broken experience, continuously test on real mobile and desktop devices during development rather than just relying on Chrome. Leverage services like BrowserStack to efficiently test across browser matrixes.
Pro Tip: Identify your site analytics top 5 browsers and test specifically on those platforms.
2. Responsiveness and Layout Failure
With the majority of traffic now originating from mobile, ensuring your UI responds properly across all screen sizes is essential. Some of the responsive issues I often catch during testing include:
- Horizontal scroll bars appearing on mobile devices
- Elements overlapping or stacking while resizing
- Font sizes incorrectly scaling between breakpoints
- Images blurring, stretching and distorting as window sizes change
To crush these bugs, continuously resize and test directly on physical mobile, tablet and desktop devices. Avoid developing solely on chrome mobile emulator which often misses responsiveness edge cases. Leverage tools like our free Responsive Checker to analyze sizing issues.
Pro Tip: Set width breakpoint values on common device sizes – 320px, 768px etc rather than round numbers.
3. Dysfunctional UI Elements
A single non-working UI element can bring an entire flow to a grinding halt for users. I‘ve seen everything from dead buttons and links going nowhere to empty dropdowns and error messages appearing randomly on form submits.
To ensure functionality, meticulously click and test every interactive element on every screen. Enter unexpected data into forms, let validation checks trigger, and push into edge case territory. Automated testing scripts can assist by programmatically interacting with elements at scale.
Fixing a faulty Submit button after launch could require an emergency hotfix deployment – so prioritize testing flows early and often!
Pro Tip: Scope smoke tests to click every button across core happy paths before adding conditional logic.
4. Invalid Form Field Validation
Form validation frequently trips up product teams when users start entering data in unexpected formats. Bugs here feel especially sloppy and unpolished to end users.
Common form issues I encounter include:
- No validation causing database crashes on bad data
- Email addresses accepted in incorrect formats
- Numbers parsed into text fields
- Special characters and xss attacks breaking functionality
Shield your forms by:
- Adding strict validation rules on front and backend
- Testing intentionally with invalid and edge case data
- Providing clear error messages guiding users
You should meticulously test real world scenarios – copy/paste long text into inputs, upload insane file types, leave fields blank and every combination.
Pro Tip: Disable submit buttons until all form fields are valid for cleaner user experience.
5. Accessibility Blindspots
Accessibility bugs blocking disabled users tend to only get tested at the end, leading to exclusions for segments of customers. Some common issues I see include:
- Images lacking alternative text descriptions
- Low color contrast ratios failing standards
- Videos without captions
- Keyboard navigation not supported
Build accessibility testing into your sprint cycles with tools like aXe and WAVE to scan for warnings. Validate compliance with web standards such as ADA, Section 508 and WCAG 2.1 criteria.
Pro Tip: Ensure your site works properly when zoomed to 400% and navigate via keyboard only.
6. UI Consistency Gone Haywire
When different developers own screens in isolation, consistency bugs start to erode trust in an otherwise polished UI. Examples include:
- Mismatched branding color palettes
- Unexpected padding and margin changes
- Font sizes jumping
- Tone/voice drastically shifting
Create UX documentation like style guides and component libraries to align on standards upfront. Utilize design systems and visual regression tools to catch inconsistencies.
Pro Tip: Extend your testing to documentation sites, marketing pages and emails to fix fragmentation.
7. Performance Bottlenecks
With 59% of mobile users abandoning sites taking over 3 seconds to load, speed is a make-or-break quality for apps. I frequently catch performance issues like:
- Images uncompressed and weighing pages down
- Javascript files blocking rendering
- Too many unnecessary fonts loading
- Unoptimized code and images bloating bundle size
Test using real world environments on average devices instead of overpowered machines and fast WiFi. Simulate networks with throttling tools to expose optimization gaps. Waterfall charts will visually pinpoint sinks.
Pro Tip: Set a performance budget baseline and enforce with automated testing in CI pipelines.
8. Device-Specific Gremlins
Even with perfect iPhone test coverage, bugs can creep in on less obvious devices. For example – Samsung Galaxy owners were recently locked out of Twitter due to an Android 12 bug.
To catch device gremlins:
- Expand testing to more obscure real devices
- Balance test device diversity beyond just iPhones
- Exploratory and ad-hoc testing tend to reveal device issues
Dig out that Windows Phone collecting dust in storage – it might end up saving your app!
Pro Tip: Analyze analytics traffic to find less common but consistent device users to test.
9. Flaky Test Automation
A frustrating test automation trend I see is teams spending disproportionate time battling script maintenance issues. Tests pass one run then fail mysteriously the next with no code changes.
Signs of troublesome test debt:
- Brittle locators requiring constant repairs
- Failure analysis eating up more time than writing tests
- Deleted scripts no longer relevant to current UI
- Alerts and popups causing false failures
Refactor flakiness by:
- Removing overlapping and obsolete tests
- Implementing self-healing locators
- Increasing waits and syncs across steps
- Locking down test environments between runs
Don‘t let your automation hygiene languish. Set regular dedicated days for script improvements.
Pro Tip: Analyze failure rates over time to quantify automation quality improvement.
10. Visual Defects Destroying Polish
With pixel perfect designs and expectations rising, even tiny visual inconsistencies can torment discerning users. But when deadlines loom, visual nitpicks tend to get deprioritized.
Micro defects that seem harmless on surface but accumulate over time:
- Font kerning issues
- One pixel borders slightly off
- Color shades that don‘t match spec
- Unaligned elements by a hair
- Incorrect icon sizes between platforms
Leverage visual regression testing and manual aesthetic testing each sprint to catch imperfections. Don‘t ignore those tiny paper cuts – fix visual defects before they leave your doors!
Pro Tip: Require a dedicated QA polish pass focused only on closing visual defects before launch.
An Ounce of Prevention
By understanding the most prevalent categories of UI bugs infiltrating releases and frustrating users, your team can now build out comprehensive pre-flight checklists tailored to block these issues.
Shifting testing upstream rather than as an afterthought will prevent exponentially more quality issues over your product lifetime. Prioritize regular cross-browser, device, localization, accessibility, performance, automation and visual testing between sprints.
Deliver stable and polished user experiences that delight customers by stomping out UI bugs before they spread. Squash them ruthlessly and decisively through prevention, detection and remediation testing techniques.
To summarize – here is my recommended anti-bug checklist:
[Top 10 UI Bug Prevention Checklist]
- Cross-browser testing on real devices
- Responsiveness across screen sizes
- Verify all elements function properly
- Validate form field handling
- Accessibility standards testing
- UI consistency compliance
- Performance benchmarking
- Test across diverse mobile devices
- Reliable test automation
- Eliminate visual defects
Now get out there, find those pesky UI bugs plaguing your team and annihilate them before they reach your customers! Share your top tips and tricks for identifying issues early in the comments below. Smash those bugs!
