Background size in CSS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the CSS property background-size control?

It controls the size of the background image inside an element, letting you decide how big or small the image appears.

beginner

What does background-size: cover; do?

It makes the background image cover the entire element area, cropping parts if needed, so no empty space is visible.

intermediate

What is the difference between background-size: contain; and background-size: cover;?

contain fits the whole image inside the element without cropping, possibly leaving empty space. cover fills the element fully but may crop the image.

beginner

How can you set a background image to be exactly 100px wide and 50px tall?

Use background-size: 100px 50px; to set the width and height explicitly.

beginner

What happens if you set background-size: auto;?

The background image keeps its original size without scaling.

Which background-size value makes the image fill the element completely, possibly cropping it?

A auto

B contain

C cover

D inherit

cover scales the image to fill the element fully, cropping if needed.

What does background-size: contain; do?

A Scales the image to fit inside the element without cropping

B Keeps the image original size

C Repeats the image to fill the element

D Scales the image to fill the element and crop if needed

contain fits the entire image inside the element without cropping.

How do you set a background image size to 50% width and 100% height of the element?

A background-size: auto;

B background-size: 100% 50%;

C background-size: cover;

D background-size: 50% 100%;

The first value is width, second is height, so 50% width and 100% height.

If you want the background image to keep its original size, which value should you use?

A cover

B auto

C contain

D 100% 100%

auto keeps the image at its original size.

Which CSS property controls the size of a background image?

A background-size

B background-repeat

C background-position

D background-color

background-size sets how big or small the background image is.

Explain how background-size: cover; and background-size: contain; behave differently.

Think about whether the image is cropped or fully visible.

Describe how to set a background image to a specific width and height using CSS.

Remember the syntax: background-size: width height;

Practice

1. What does the CSS property background-size: cover; do to a background image?

easy

A. It repeats the image to cover the element area.

B. It stretches the image to fit the element exactly without cropping.

C. It makes the background image fill the entire element, cropping if needed.

D. It fits the whole image inside the element without cropping.

Solution

1. Step 1: Understand cover behavior

   cover scales the background image to fill the entire element area, even if some parts get cropped.

2. Step 2: Compare with other options

   contain fits the whole image inside without cropping, and repeating is controlled by background-repeat.

3. Final Answer:

   It makes the background image fill the entire element, cropping if needed. -> Option C

4. Quick Check:

   cover = fills and crops [OK]

Hint: Remember: cover fills and crops, contain fits fully [OK]

Common Mistakes:

• Confusing cover with contain
• Thinking cover repeats the image
• Assuming cover never crops

2. Which of the following is the correct CSS syntax to make a background image fit inside an element without cropping?

easy

A. background-size: contain;

B. background-size: cover;

C. background-size: fill;

D. background-size: stretch;

Solution

1. Step 1: Identify the property value for fitting without cropping

   contain scales the image to fit inside the element fully without cropping.

2. Step 2: Check other options for correctness

   cover crops, fill and stretch are invalid values for background-size.

3. Final Answer:

   background-size: contain; -> Option A

4. Quick Check:

   contain fits fully without crop [OK]

Hint: Use contain to fit fully, cover to fill and crop [OK]

Common Mistakes:

• Using invalid values like fill or stretch
• Mixing up cover and contain
• Forgetting semicolon in syntax

3. Given this CSS:

div {
  width: 200px;
  height: 100px;
  background-image: url('flower.jpg');
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
}

What will the background image look like inside the div?

medium

A. The image will fill the div completely, cropping parts if needed.

B. The whole image will fit inside the div, centered, with possible empty space.

C. The image will repeat to fill the div area.

D. The image will stretch to exactly 200px by 100px, ignoring aspect ratio.

Solution

1. Step 1: Analyze background-size: contain; effect

   This makes the entire image fit inside the div without cropping, preserving aspect ratio.

2. Step 2: Consider other properties

   background-repeat: no-repeat; prevents tiling, and background-position: center; centers the image. So empty space may appear if aspect ratios differ.

3. Final Answer:

   The whole image will fit inside the div, centered, with possible empty space. -> Option B

4. Quick Check:

   contain fits fully, no repeat, centered [OK]

Hint: Contain fits whole image, no repeat means no tiling [OK]

Common Mistakes:

• Assuming contain crops the image
• Thinking image repeats by default
• Confusing stretch with contain

4. This CSS code is intended to make a background image fill the element without repeating, but it doesn't work as expected:

div {
  background-image: url('tree.jpg');
  background-size: 100%;
  background-repeat: no-repeat;
}

What is the problem?

medium

A. background-size: 100%; only sets width, height is auto, so it may not fill the entire element.

B. The URL is missing quotes around the image path.

C. background-repeat must be set to repeat-x to fill horizontally.

D. The property background-size does not accept percentages.

Solution

1. Step 1: Understand background-size: 100%; meaning

   Setting only one value means width is 100% of element, height auto to keep aspect ratio, so it may not fill the entire element.

2. Step 2: Check other options

   URL quotes are optional but recommended, background-repeat: no-repeat; disables tiling correctly, and background-size accepts percentages.

3. Final Answer:

   background-size: 100%; only sets width, height is auto, so it may not fill the entire element. -> Option A

4. Quick Check:

   One value sets width only, height auto [OK]

Hint: Two values needed to set both width and height [OK]

Common Mistakes:

• Using one value thinking it sets both width and height
• Ignoring aspect ratio effects
• Misunderstanding background-repeat options

5. You want a background image to always cover the entire element area on all screen sizes, but never be cropped. Which CSS approach is best?

hard

A. Use background-size: contain; and background-repeat: no-repeat;.

B. Use background-size: cover; and background-position: center;.

C. Use background-size: auto; and background-repeat: repeat;.

D. Use background-size: 100% 100%; to stretch image exactly.

Solution

1. Step 1: Understand the requirement

   The image must always fill the entire element area (no empty space) on all screen sizes without cropping (whole image visible).

2. Step 2: Evaluate options

   contain fits whole image but may leave empty space; cover fills but crops; 100% 100% stretches whole image to exactly fill without cropping or space; auto repeat tiles.

3. Final Answer:

   Use background-size: 100% 100%; to stretch image exactly. -> Option D

4. Quick Check:

   100% 100% fills exactly, no crop [OK]

Hint: 100% 100% stretches to fill exactly, no crop or space [OK]

Common Mistakes:

• Choosing cover which crops
• Choosing contain which leaves space
• Using repeat which tiles