Text decoration in CSS - Performance & Optimization

Performance: Text decoration

LOW IMPACT

Text decoration affects the paint and composite stages of rendering, impacting how quickly styled text appears and updates on screen.

Applying underline style to text

CSS

p { text-decoration: underline solid black; }

Simple solid underline uses less paint and compositing resources.

📈 Performance Gainreduces paint and composite cost by ~50%

Applying underline style to text

CSS

p { text-decoration: underline wavy red; }

Complex text-decoration styles like wavy lines trigger more paint and compositing work.

📉 Performance Costtriggers 1 extra paint and composite per element

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
text-decoration: underline solid	none	none	low paint cost	[OK] Good
text-decoration: underline wavy	none	none	higher paint cost	[X] Bad

Rendering Pipeline

Text decoration styles are applied during style calculation and affect paint and composite stages. Complex decorations increase paint area and compositing layers.

→Style Calculation

→Paint

→Composite

⚠️ BottleneckPaint

Core Web Vital Affected

CLS

Text decoration affects the paint and composite stages of rendering, impacting how quickly styled text appears and updates on screen.

Optimization Tips

1Prefer simple text-decoration styles like solid underline for better paint performance.

2Avoid animating text-decoration properties to reduce paint and composite overhead.

3Use browser DevTools Performance panel to monitor paint and composite costs of text styles.

Performance Quiz - 3 Questions

Which text-decoration style generally causes less paint work?

A Double underline

B Wavy underline

C Solid underline

D Dotted underline

DevTools: Performance

How to check: Record a performance profile while interacting with text that has decoration. Look for paint and composite events in the flame chart.

What to look for: High paint or composite times indicate costly text-decoration styles.

Practice

1. Which CSS property is used to add an underline to text?

easy

A. text-transform

B. font-style

C. line-height

D. text-decoration

Solution

1. Step 1: Identify the property for text lines

   The property text-decoration controls lines like underline, overline, and line-through on text.

2. Step 2: Confirm the underline effect

   Using text-decoration: underline; adds an underline to the text.

3. Final Answer:

   text-decoration -> Option D

4. Quick Check:

   Underline = text-decoration [OK]

Hint: Underline text with text-decoration property [OK]

Common Mistakes:

• Confusing font-style with underline
• Using text-transform which changes case
• Using line-height which controls spacing

2. Which of the following is the correct syntax to add a line-through effect to text in CSS?

easy

A. text-decoration: strike;

B. text-decoration: line-through;

C. text-decoration: crossed;

D. text-decoration: overline;

Solution

1. Step 1: Recall valid text-decoration values

   The valid values for text-decoration include underline, overline, and line-through.

2. Step 2: Match the line-through effect

   The correct value to cross out text is line-through. Other options like strike or crossed are invalid.

3. Final Answer:

   text-decoration: line-through; -> Option B

4. Quick Check:

   Line-through = line-through [OK]

Hint: Use line-through for strike effect in text-decoration [OK]

Common Mistakes:

• Using invalid values like strike or crossed
• Confusing overline with line-through
• Missing the colon or semicolon in syntax

3. What will be the visual effect of this CSS on a paragraph?

p { text-decoration: underline overline; }

medium

A. The paragraph text will only have an overline.

B. The paragraph text will only have an underline.

C. The paragraph text will have both an underline and an overline.

D. The paragraph text will have no decoration.

Solution

1. Step 1: Understand multiple values in text-decoration

   The text-decoration property can accept multiple values separated by spaces to combine effects.

2. Step 2: Apply underline and overline together

   Using underline overline applies both lines above and below the text simultaneously.

3. Final Answer:

   The paragraph text will have both an underline and an overline. -> Option C

4. Quick Check:

   Multiple decorations combine = both lines [OK]

Hint: Multiple text-decoration values add multiple lines [OK]

Common Mistakes:

• Assuming only the first value applies
• Thinking values override each other
• Confusing overline with underline

4. Identify the error in this CSS code snippet:

h1 { text-decoration: underlined; }

medium

A. The value 'underlined' is invalid for text-decoration.

B. The property name should be 'text-decoration-line'.

C. Missing semicolon after the value.

D. The selector 'h1' is incorrect.

Solution

1. Step 1: Check valid values for text-decoration

   Valid values include underline, overline, line-through, but not underlined.

2. Step 2: Confirm property and syntax correctness

   The property text-decoration is correct and semicolon is present. The selector h1 is valid.

3. Final Answer:

   The value 'underlined' is invalid for text-decoration. -> Option A

4. Quick Check:

   Valid values only = underline, overline, line-through [OK]

Hint: Use exact values: underline, not underlined [OK]

Common Mistakes:

• Adding 'd' to underline value
• Confusing property names
• Ignoring semicolon errors

5. You want to style a link so it has a red underline only when hovered, and no decoration normally. Which CSS code achieves this?

hard

A. a { text-decoration: none; } a:hover { text-decoration: underline; text-decoration-color: red; }

B. a { text-decoration: underline red; } a:hover { text-decoration: none; }

C. a { text-decoration-color: red; } a:hover { text-decoration: none; }

D. a { text-decoration: underline; } a:hover { text-decoration-color: red; }

Solution

1. Step 1: Set no decoration normally

   Use text-decoration: none; on the link to remove underline by default.

2. Step 2: Add red underline on hover

   On a:hover, add text-decoration: underline; and set text-decoration-color: red; to color the underline red.

3. Final Answer:

   a { text-decoration: none; } a:hover { text-decoration: underline; text-decoration-color: red; } -> Option A

4. Quick Check:

   None normally + red underline on hover = a { text-decoration: none; } a:hover { text-decoration: underline; text-decoration-color: red; } [OK]

Hint: Use none normally, underline + color on hover [OK]

Common Mistakes:

• Setting underline always, not only on hover
• Using text-decoration-color without underline
• Reversing hover and normal styles