CSS Overflow Debugging

Systematic approach to diagnosing when content overflows containers, creates unwanted scrollbars, or breaks layouts.

Common Overflow Causes:

• Fixed dimensions: Width/height too small for content
• White-space: white-space: nowrap preventing text wrapping
• Flexbox: Items not shrinking (flex-shrink: 0)
• Grid: Content larger than track sizes
• Margins: Collapsing margins creating unexpected spacing

Debugging Process:

1. Identify overflow direction: Horizontal vs vertical
2. Check container constraints: Fixed width/height values
3. Examine content: Text length, image sizes, child elements
4. Test overflow properties: overflow: hidden/scroll/auto

Diagnostic CSS:

/* Highlight overflowing elements */
* {
  box-sizing: border-box !important;
  outline: 1px solid red !important;
}
 
/* Prevent horizontal overflow temporarily */
* { max-width: 100% !important; }

Mental Model: Think of containers as picture frames - content either fits, gets cropped, or breaks the frame.

Solutions by Context:

• Text: word-wrap: break-word, hyphens: auto
• Images: max-width: 100%, object-fit: contain
• Flex: min-width: 0 on flex items

Related: Box Model Fundamentals, CSS Layout Debugging Strategy