When 1 px border is added to a div, the div size increases, but I don't want that to happen

css

responsive-design

best-practices

developer-tools

byNikita Barsukov·Jan 5, 2025

To ensure your div doesn't grow with a 1px border, apply box-sizing: border-box;. This CSS property includes the border in the element's specified width and height.

div {
   width: 100px; /* Absolutely, it's final! Even with border */
   height: 100px; /* Again, it's final! I've checked! */
   border: 1px solid black;
   box-sizing: border-box; /* The secret sauce */
}

This way, the div's dimensions are a solid 100px square, including the border. The border is part of its dimensions – neat right?

Strategies to prevent size changes when adding borders

Using the 'outline' property

The outline property is like the border's easygoing cousin. It looks similar but doesn't cause any size fuss:

div {
  outline: 1px solid black; /* Trust me, it's size safe! */
}

The invisible shield: transparent borders

Transparent borders let you have your cake and eat it. You add borders but they are invisible:

div {
  border: 1px solid transparent; /* Now you see it. No, you don't! */
}

Switching the border color to match the background color is another sneaky trick up your sleeve.

Adjusting padding and external frameworks: play nice!

Subtract 2px from your dimensions or soften up your padding by 1px on border addition especially when dealing with external frameworks that override your rules.

Embracing the old: cross-browser support

Not everybody is on the latest browser, and we have to look out for our old browser buddies:

div {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

Practical considerations when using css to prevent size changes from borders

Develop like a pro: use developer tools

Developer tools like Firebug or Chrome DevTools are like X-ray glasses. They help unveil how dimensions, including borders, are rendered in different browsers. Trust me, these will be your best friend for fine-tuning your layout.

The changing tides: dynamic changes with CSS classes

Change is the only constant, even in coding. When borders change e.g., element selection, consider toggling classes:

.selected {
  border: 1px solid black;
}

Go with the flow: flexible strategies for responsive designs

Avoid being the square peg in the round hole. Ditch hardcoded widths, and take a smoother path with padding and margins. Responsive designs love it!

Hints for multiple backgrounds

If multiple background images or colors are your thing, then transparent borders will be your bread and butter.

Picky about your borders?

Maybe you only want borders on top and bottom. Just get what you want with border-top and border-bottom:

div {
  border-top: 1px solid black; /* All hail the top border! */
  border-bottom: 1px solid black; /* Bottom border is not forgotten! */
}

explain-codes / Css / When 1 px border is added to a div, the div size increases, but I don't want that to happen

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