The z-index property does not seem to function properly when used in conjunction

Question

The z-index property does not seem to function properly when used in conjunction

I am experiencing an issue with the z-indexes of two divs: one with default positioning and the other with a fixed position.

No matter how I adjust the z-index values, it appears impossible to make the fixed-positioned element go behind the statically positioned element.

#over {
  width: 600px;
  z-index: 10;
}

#under {
  position: fixed;
  top: 5px;
  width: 420px;
  left: 20px;
  border: 1px solid;
  height: 10%;
  background: #fff;
  z-index: 1;
}

<div id="over">
  Hello Hello HelloHelloHelloHelloHello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello
</div>

<div id="under"></div>

You can view this on jsfiddle here: http://jsfiddle.net/mhFxf/

To work around this issue, I have used position:absolute on the static element. However, I am curious to understand why this behavior is occurring.

(While there is a similar question on stackoverflow (Fixed Positioning breaking z-index), I have not found a satisfactory answer, which is why I am posting my query here along with example code)

css z-index

Answer 1

Answer №1

To enhance the appearance of #over, include the CSS property position: relative in the code snippet below:

#over {
  width: 600px;
  z-index: 10;
  position: relative;
}

#under {
  position: fixed;
  top: 14px;
  width: 415px;
  left: 53px;
  border: 1px solid;
  height: 10%;
  background: #f0f;
  z-index: 1;
}

<div id="over">
  <P>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
    </>
</div>

<div id="under"></div>

Fiddle

Answer 2

To enhance the appearance of #over, include the CSS property position: relative in the code snippet below:

#over {
  width: 600px;
  z-index: 10;
  position: relative;
}

#under {
  position: fixed;
  top: 14px;
  width: 415px;
  left: 53px;
  border: 1px solid;
  height: 10%;
  background: #f0f;
  z-index: 1;
}

<div id="over">
  <P>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
    </>
</div>

<div id="under"></div>

Fiddle

Answer 3

Answer №2

There are various ways to solve this question, but understanding the stacking rules is key to finding the optimal solution for your needs.

Possible Solutions

The <html> element serves as the primary stacking context, so adhering to the stacking rules within a stacking context will determine the order in which elements are stacked.

The root element of the stacking context (the <html> element here)

Positioned elements (and their children) with negative z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)

Non-positioned elements (ordered by HTML appearance)

Positioned elements (and their children) with a z-index value of auto (ordered by HTML appearance)

Positioned elements (and their children) with positive z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)

Here are some steps you can take:

Assign a z-index of -1 to #under to position it behind the non-positioned #over element
Set the position of #over to relative so that rule 5 applies to it

Understanding the Root Issue

Developers should be aware of the following points before attempting to alter the stacking order of elements.

Formation of a stacking context
- The <html> element serves as the default root element and initial stacking context
Ordering within a stacking context

The information on stacking order and stacking context rules mentioned above has been sourced from this link

Creation of a Stacking Context

When an element functions as the document's root element (such as the <html> element)
When an element has a position other than static and a z-index aside from auto
When an element possesses an opacity less than 1
Various modern CSS properties also establish stacking contexts, including: transforms, filters, css-regions, paged media, among others. https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Positioning/Understanding_z_index/The_stacking_context
In essence, if a CSS property necessitates rendering offscreen, it typically initiates a new stacking context.

Element Ordering within a Stacking Context

The sequence of elements:

The stacking context’s root element (defaulted to the <html> element as the sole stacking context, though any element can serve as a stacking context root, per the aforementioned rules)
- You cannot place a child element behind a root stacking context element
Positioned elements (and their children) with negative z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)
Non-positioned elements (ordered by HTML appearance)
Positioned elements (and their children) with a z-index value of auto (ordered by HTML appearance)
Positioned elements (and their children) with positive z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)

Answer 4

There are various ways to solve this question, but understanding the stacking rules is key to finding the optimal solution for your needs.

Possible Solutions

The <html> element serves as the primary stacking context, so adhering to the stacking rules within a stacking context will determine the order in which elements are stacked.

The root element of the stacking context (the <html> element here)

Positioned elements (and their children) with negative z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)

Non-positioned elements (ordered by HTML appearance)

Positioned elements (and their children) with a z-index value of auto (ordered by HTML appearance)

Positioned elements (and their children) with positive z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)

Here are some steps you can take:

Assign a z-index of -1 to #under to position it behind the non-positioned #over element
Set the position of #over to relative so that rule 5 applies to it

Understanding the Root Issue

Developers should be aware of the following points before attempting to alter the stacking order of elements.

Formation of a stacking context
- The <html> element serves as the default root element and initial stacking context
Ordering within a stacking context

The information on stacking order and stacking context rules mentioned above has been sourced from this link

Creation of a Stacking Context

When an element functions as the document's root element (such as the <html> element)
When an element has a position other than static and a z-index aside from auto
When an element possesses an opacity less than 1
Various modern CSS properties also establish stacking contexts, including: transforms, filters, css-regions, paged media, among others. https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Positioning/Understanding_z_index/The_stacking_context
In essence, if a CSS property necessitates rendering offscreen, it typically initiates a new stacking context.

Element Ordering within a Stacking Context

The sequence of elements:

The stacking context’s root element (defaulted to the <html> element as the sole stacking context, though any element can serve as a stacking context root, per the aforementioned rules)
- You cannot place a child element behind a root stacking context element
Positioned elements (and their children) with negative z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)
Non-positioned elements (ordered by HTML appearance)
Positioned elements (and their children) with a z-index value of auto (ordered by HTML appearance)
Positioned elements (and their children) with positive z-index values (higher values take precedence over lower ones; elements with the same value are stacked based on HTML appearance)

Answer 5

Answer №3

When the over div lacks a positioning, the z-index is unable to determine how and where to place it (and in relation to what?). To resolve this issue, simply change the over div's position to relative. This will prevent any undesired effects on that div and allow the under div to follow your instructions.

You can view an example of this solution on jsfiddle here.

Answer 6

When the over div lacks a positioning, the z-index is unable to determine how and where to place it (and in relation to what?). To resolve this issue, simply change the over div's position to relative. This will prevent any undesired effects on that div and allow the under div to follow your instructions.

You can view an example of this solution on jsfiddle here.

Answer 7

Answer №4

Beware of misinformation in this response. Take a look at @Dansingerman's input for accurate details and examples.

Remember, the z-index property is only effective within specific positioning contexts like relative, fixed, or absolute.

It's important to note that the z-index value for a relatively positioned div does not impact the stacking order of absolutely or fixedly positioned elements.

Answer 8

Beware of misinformation in this response. Take a look at @Dansingerman's input for accurate details and examples.

Remember, the z-index property is only effective within specific positioning contexts like relative, fixed, or absolute.

It's important to note that the z-index value for a relatively positioned div does not impact the stacking order of absolutely or fixedly positioned elements.

Answer 9

Answer №5

To solve this issue, make sure to assign a negative z-index value to the #under element, such as -1.

The reason behind this is that the z-index property does not work when the position of an element is set to static, which is actually the default value in CSS. Therefore, even if you set a higher z-index for the #over element, both elements will still have a z-index of 1. By giving the #under element a negative value, it will be positioned behind any element with a z-index: 1;, such as the #over element.

Answer 10

To solve this issue, make sure to assign a negative z-index value to the #under element, such as -1.

The reason behind this is that the z-index property does not work when the position of an element is set to static, which is actually the default value in CSS. Therefore, even if you set a higher z-index for the #over element, both elements will still have a z-index of 1. By giving the #under element a negative value, it will be positioned behind any element with a z-index: 1;, such as the #over element.

Answer 11

Answer №6

While constructing a navigation menu, I encountered an issue with hidden content due to the implementation of overflow: hidden in the CSS. Initially thought to be related to z-index, it turned out that the problem lied in hiding elements outside of the navigation container.

Answer 12

While constructing a navigation menu, I encountered an issue with hidden content due to the implementation of overflow: hidden in the CSS. Initially thought to be related to z-index, it turned out that the problem lied in hiding elements outside of the navigation container.

Answer 13

Answer №7

When elements are positioned outside the regular flow, they have the potential to overlap with other elements.

Based on the information provided in the Overlapping Elements section found at http://web.archive.org/web/20130501103219/http://w3schools.com/css/css_positioning.asp

Answer 14

When elements are positioned outside the regular flow, they have the potential to overlap with other elements.

Based on the information provided in the Overlapping Elements section found at http://web.archive.org/web/20130501103219/http://w3schools.com/css/css_positioning.asp

Answer 15

Answer №8

the behavior of certain CSS elements, such as fixed and absolute elements, is described in the CSS Spec:

These elements act as if they are independent from the rest of the document and are placed within the nearest fixed/absolute positioned parent (paraphrased).

This can complicate z-index calculations. I found a solution for my issue by dynamically creating a container element in the body and moving all elements with the class "my-fixed-ones" inside that new container at the body level.

Answer 16

the behavior of certain CSS elements, such as fixed and absolute elements, is described in the CSS Spec:

These elements act as if they are independent from the rest of the document and are placed within the nearest fixed/absolute positioned parent (paraphrased).

This can complicate z-index calculations. I found a solution for my issue by dynamically creating a container element in the body and moving all elements with the class "my-fixed-ones" inside that new container at the body level.

The z-index property does not seem to function properly when used in conjunction

Answer №1

Answer №2

Possible Solutions

Understanding the Root Issue

Creation of a Stacking Context

Element Ordering within a Stacking Context

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

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