'How to use z-index in svg elements?

I'm using the svg circles in my project like this,

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 160 120">
    <g>
        <g id="one">
            <circle fill="green" cx="100" cy="105" r="20" />
        </g>
        <g id="two">
            <circle fill="orange" cx="100" cy="95" r="20" />
        </g>
    </g>
</svg>

And I'm using the z-index in the g tag to show the elements the first. In my project I need to use only z-index value, but I can't use the z-index to my svg elements. I have googled a lot but I didn't find anything relatively. So please help me to use z-index in my svg.

Here is the DEMO.

javascriptjquerysvgz-index


Solution 1:[1]

Specification

In the SVG specification version 1.1 the rendering order is based on the document order:

first element -> "painted" first

Reference to the SVG 1.1. Specification

3.3 Rendering Order

Elements in an SVG document fragment have an implicit drawing order, with the first elements in the SVG document fragment getting "painted" first. Subsequent elements are painted on top of previously painted elements.

Solution (cleaner-faster)

You should put the green circle as the latest object to be drawn. So swap the two elements.

<svg xmlns="http://www.w3.org/2000/svg" viewBox="30 70 160 120"> 
   <!-- First draw the orange circle -->
   <circle fill="orange" cx="100" cy="95" r="20"/> 

   <!-- Then draw the green circle over the current canvas -->
   <circle fill="green" cx="100" cy="105" r="20"/> 
</svg>

Here the fork of your jsFiddle.

Solution (alternative)

The tag use with the attribute xlink:href (just href for SVG 2) and as value the id of the element. Keep in mind that might not be the best solution even if the result seems fine. Having a bit of time, here the link of the specification SVG 1.1 "use" Element.

Purpose:

To avoid requiring authors to modify the referenced document to add an ID to the root element.

<svg xmlns="http://www.w3.org/2000/svg" viewBox="30 70 160 120">
    <!-- First draw the green circle -->
    <circle id="one" fill="green" cx="100" cy="105" r="20" />
    
    <!-- Then draw the orange circle over the current canvas -->
    <circle id="two" fill="orange" cx="100" cy="95" r="20" />
    
    <!-- Finally draw again the green circle over the current canvas -->
    <use xlink:href="#one"/>
</svg>

Notes on SVG 2

SVG 2 Specification is the next major release and still supports the above features.

3.4. Rendering order

Elements in SVG are positioned in three dimensions. In addition to their position on the x and y axis of the SVG viewport, SVG elements are also positioned on the z axis. The position on the z-axis defines the order that they are painted.

Along the z axis, elements are grouped into stacking contexts.

3.4.1. Establishing a stacking context in SVG

...

Stacking contexts are conceptual tools used to describe the order in which elements must be painted one on top of the other when the document is rendered, ...

Solution 2:[2]

As others here have said, z-index is defined by the order the element appears in the DOM. If manually reordering your html isn't an option or would be difficult, you can use D3 to reorder SVG groups/objects.

Use D3 to Update DOM Order and Mimic Z-Index Functionality

Updating SVG Element Z-Index With D3

At the most basic level (and if you aren't using IDs for anything else), you can use element IDs as a stand-in for z-index and reorder with those. Beyond that you can pretty much let your imagination run wild.

Examples in code snippet

var circles = d3.selectAll('circle')
var label = d3.select('svg').append('text')
    .attr('transform', 'translate(' + [5,100] + ')')

var zOrders = {
    IDs: circles[0].map(function(cv){ return cv.id; }),
    xPos: circles[0].map(function(cv){ return cv.cx.baseVal.value; }),
    yPos: circles[0].map(function(cv){ return cv.cy.baseVal.value; }),
    radii: circles[0].map(function(cv){ return cv.r.baseVal.value; }),
    customOrder: [3, 4, 1, 2, 5]
}

var setOrderBy = 'IDs';
var setOrder = d3.descending;

label.text(setOrderBy);
circles.data(zOrders[setOrderBy])
circles.sort(setOrder);
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 400 100"> 
  <circle id="1" fill="green" cx="50" cy="40" r="20"/> 
  <circle id="2" fill="orange" cx="60" cy="50" r="18"/>
  <circle id="3" fill="red" cx="40" cy="55" r="10"/> 
  <circle id="4" fill="blue" cx="70" cy="20" r="30"/> 
  <circle id="5" fill="pink" cx="35" cy="20" r="15"/> 
</svg>

The basic idea is:

  1. Use D3 to select the SVG DOM elements.

    var circles = d3.selectAll('circle')

  2. Create some array of z-indices with a 1:1 relationship with your SVG elements (that you want to reorder). Z-index arrays used in the examples below are IDs, x & y position, radii, etc....

    var zOrders = {
    IDs: circles[0].map(function(cv){ return cv.id; }),
    xPos: circles[0].map(function(cv){ return cv.cx.baseVal.value; }),
    yPos: circles[0].map(function(cv){ return cv.cy.baseVal.value; }),
    radii: circles[0].map(function(cv){ return cv.r.baseVal.value; }),
    customOrder: [3, 4, 1, 2, 5]
}

  3. Then, use D3 to bind your z-indices to that selection.

    circles.data(zOrders[setOrderBy]);

  4. Lastly, call D3.sort to reorder the elements in the DOM based on the data.

    circles.sort(setOrder);

Examples

enter image description here

  • You can stack by ID

enter image description here

  • With leftmost SVG on top

enter image description here

  • Smallest radii on top

enter image description here

  • Or Specify an array to apply z-index for a specific ordering -- in my example code the array [3,4,1,2,5] moves/reorders the 3rd circle (in the original HTML order) to be 1st in the DOM, 4th to be 2nd, 1st to be 3rd, and so on...

Solution 3:[3]

Try to invert #one and #two. Have a look to this fiddle : http://jsfiddle.net/hu2pk/3/

Update

In SVG, z-index is defined by the order the element appears in the document. You can have a look to this page too if you want : https://stackoverflow.com/a/482147/1932751

Solution 4:[4]

You can use use.

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 160 120">
    <g>
        <g id="one">
            <circle fill="green" cx="100" cy="105" r="20" />
        </g>
        <g id="two">
            <circle fill="orange" cx="100" cy="95" r="20" />
        </g>
    </g>
    <use xlink:href="#one" />
</svg>

The green circle appears on top.
jsFiddle

Solution 5:[5]

Using D3:

If you want to re-inserts each selected element, in order, as the last child of its parent. 

selection.raise()

Solution 6:[6]

As discussed, svgs render in order and don't take z-index into account (for now). Maybe just send the specific element to the bottom of its parent so that it'll render last.

function bringToTop(targetElement){
  // put the element at the bottom of its parent
  let parent = targetElement.parentNode;
  parent.appendChild(targetElement);
}

// then just pass through the element you wish to bring to the top
bringToTop(document.getElementById("one"));

Worked for me.

Update

If you have a nested SVG, containing groups, you'll need to bring the item out of its parentNode.

function bringToTopofSVG(targetElement){
  let parent = targetElement.ownerSVGElement;
  parent.appendChild(targetElement);
}

A nice feature of SVG's is that each element contains it's location regardless of what group it's nested in :+1:

Solution 7:[7]

Using D3:

If you want to add the element in the reverse order to the data, use:

.insert('g', ":first-child")

Instead of .append('g')

Adding an element to top of a group element

Solution 8:[8]

There is no z-index for svgs. But svg determines which of your elements are the uppermost by theire position in the DOM. Thus you can remove the Object and place it to the end of the svg making it the "last rendered" element. That one is then rendered "topmost" visually.

Using jQuery:

function moveUp(thisObject){
    thisObject.appendTo(thisObject.parents('svg>g'));
}

usage:

moveUp($('#myTopElement'));

Using D3.js:

d3.selection.prototype.moveUp = function() {
    return this.each(function() {
        this.parentNode.appendChild(this);
    });
};

usage:

myTopElement.moveUp();

Solution 9:[9]

The clean, fast, and easy solutions posted as of the date of this answer are unsatisfactory. They are constructed over the flawed statement that SVG documents lack z order. Libraries are not necessary either. One line of code can perform most operations to manipulate the z order of objects or groups of objects that might be required in the development of an app that moves 2D objects around in an x-y-z space.

Z Order Definitely Exists in SVG Document Fragments

What is called an SVG document fragment is a tree of elements derived from the base node type SVGElement. The root node of an SVG document fragment is an SVGSVGElement, which corresponds to an HTML5 <svg> tag. The SVGGElement corresponds to the <g> tag and permits aggregating children.

Having a z-index attribute on the SVGElement as in CSS would defeat the SVG rendering model. Sections 3.3 and 3.4 of W3C SVG Recommendation v1.1 2nd Edition state that SVG document fragments (trees of offspring from an SVGSVGElement) are rendered using what is called a depth first search of the tree. That scheme is a z order in every sense of the term.

Z order is actually a computer vision shortcut to avoid the need for true 3D rendering with the complexities and computing demands of ray tracing. The linear equation for the implicit z-index of elements in an SVG document fragment.

z-index = z-index_of_svg_tag + depth_first_tree_index / tree_node_qty

This is important because if you want to move a circle that was below a square to above it, you simply insert the square before the circle. This can be done easily in JavaScript.

Supporting Methods

SVGElement instances have two methods that support simple and easy z order manipulation.

  • parent.removeChild(child)
  • parent.insertBefore(child, childRef)

The Correct Answer That Doesn't Create a Mess

Because the SVGGElement (<g> tag) can be removed and inserted just as easily as a SVGCircleElement or any other shape, image layers typical of Adobe products and other graphics tools can be implemented with ease using the SVGGElement. This JavaScript is essentially a Move Below command.

parent.insertBefore(parent.removeChild(gRobot), gDoorway)

If the layer of a robot drawn as children of SVGGElement gRobot was before the doorway drawn as children of SVGGElement gDoorway, the robot is now behind the doorway because the z order of the doorway is now one plus the z order of the robot.

A Move Above command is almost as easy.

parent.insertBefore(parent.removeChild(gRobot), gDoorway.nextSibling())

Just think a=a and b=b to remember this.

insert after = move above
insert before = move below

Leaving the DOM in a State Consistent With the View

The reason this answer is correct is because it is minimal and complete and, like the internals of Adobe products or other well designed graphics editors, leaves the internal representation in a state that is consistent with the view created by rendering.

Alternative But Limited Approach

Another approach commonly used is to use CSS z-index in conjunction with multiple SVG document fragments (SVG tags) with mostly transparent backgrounds in all but the bottom one. Again, this defeats the elegance of the SVG rendering model, making it difficult to move objects up or down in the z order.

NOTES:

  1. (https://www.w3.org/TR/SVG/render.html v 1.1, 2nd Edition, 16 August 2011)

    3.3 Rendering Order Elements in an SVG document fragment have an implicit drawing order, with the first elements in the SVG document fragment getting "painted" first. Subsequent elements are painted on top of previously painted elements.

    3.4 How groups are rendered Grouping elements such as the ‘g’ element (see container elements) have the effect of producing a temporary separate canvas initialized to transparent black onto which child elements are painted. Upon the completion of the group, any filter effects specified for the group are applied to create a modified temporary canvas. The modified temporary canvas is composited into the background, taking into account any group-level masking and opacity settings on the group.

Solution 10:[10]

Another solution would be to use divs, which do use zIndex to contain the SVG elements.As here: https://stackoverflow.com/a/28904640/4552494

Solution 11:[11]

We have already 2019 and z-index is still not supported in SVG.

You can see on the site SVG2 support in Mozilla that the state for z-index – Not implemented.

You can also see on the site Bug 360148 "Support the 'z-index' property on SVG elements" (Reported: 12 years ago).

But you have 3 possibilities in SVG to set it:

  1. With element.appendChild(aChild);
  2. With parentNode.insertBefore(newNode, referenceNode);
  3. With targetElement.insertAdjacentElement(positionStr, newElement); (No support in IE for SVG)

Interactive demo example

With all this 3 functions.

var state = 0,
    index = 100;

document.onclick = function(e)
{
    if(e.target.getAttribute('class') == 'clickable')
    {
        var parent = e.target.parentNode;

        if(state == 0)
            parent.appendChild(e.target);
        else if(state == 1)
            parent.insertBefore(e.target, null); //null - adds it on the end
        else if(state == 2)
            parent.insertAdjacentElement('beforeend', e.target);
        else
            e.target.style.zIndex = index++;
    }
};

if(!document.querySelector('svg').insertAdjacentElement)
{
    var label = document.querySelectorAll('label')[2];
    label.setAttribute('disabled','disabled');
    label.style.color = '#aaa';
    label.style.background = '#eee';
    label.style.cursor = 'not-allowed';
    label.title = 'This function is not supported in SVG for your browser.';
}
label{background:#cef;padding:5px;cursor:pointer}
.clickable{cursor:pointer}
With: 
<label><input type="radio" name="check" onclick="state=0" checked/>appendChild()</label>
<label><input type="radio" name="check" onclick="state=1"/>insertBefore()</label><br><br>
<label><input type="radio" name="check" onclick="state=2"/>insertAdjacentElement()</label>
<label><input type="radio" name="check" onclick="state=3"/>Try it with z-index</label>
<br>
<svg width="150" height="150" viewBox="0 0 150 150">
    <g stroke="none">
        <rect id="i1" class="clickable" x="10" y="10" width="50" height="50" fill="#80f"/>
        <rect id="i2" class="clickable" x="40" y="40" width="50" height="50" fill="#8f0"/>
        <rect id="i3" class="clickable" x="70" y="70" width="50" height="50" fill="#08f"/>
    </g>
</svg>

Solution 12:[12]

This is the top Google result for searches regarding z-index and SVGs. After reading all the answers, some of which are very good, I was still confused.

So for rookies like me, here is the current summary, 9 years later in 2022.

You can't use z-index with SVGs.

In SVGs, z-index is defined by the order the element appears in the document.

If you want something to appear on top, or closer to the user, draw it last or insert it before. Source

SVG 2 could support z-index but might never come out

SVG 2 is a proposal to implement that and other features but it is at risk of never moving forward.

SVG 2 reached the Candidate Recommendation stage in 2016, and was revised in 2018 and the latest draft was released on 8 June 2021. Source

However it doesn't have a lot of support and very few people are working on it. Source So don't hold your breath waiting for this.

You could use D3 but probably shouldn't

D3 a commonly used to visualize data supports z-index by binding your z-index and then sorting but it is a large and complex library and might not be the best bet if you just want a certain SVG to appear on top of a stack.

Solution 13:[13]

Push SVG element to last, so that its z-index will be in top. In SVG, there s no property called z-index. try below javascript to bring the element to top.

var Target = document.getElementById(event.currentTarget.id);
var svg = document.getElementById("SVGEditor");
svg.insertBefore(Target, svg.lastChild.nextSibling);

Target: Is an element for which we need to bring it to top svg: Is the container of elements

Solution 14:[14]

Move to front by transform:TranslateZ

Warning: Only works in FireFox

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 160 160" style="width:160px; height:160px;">
    <g style="transform-style: preserve-3d;">
        <g id="one" style="transform-style: preserve-3d;">
            <circle fill="green" cx="100" cy="105" r="20" style="transform:TranslateZ(1px);"></circle>
        </g>
        <g id="two" style="transform-style: preserve-3d;">
            <circle fill="orange" cx="100" cy="95" r="20"></circle>
        </g>
    </g>
</svg>

Solution 15:[15]

its easy to do it:

  1. clone your items
  2. sort cloned items
  3. replace items by cloned

function rebuildElementsOrder( selector, orderAttr, sortFnCallback ) {
	let $items = $(selector);
	let $cloned = $items.clone();
	
	$cloned.sort(sortFnCallback != null ? sortFnCallback : function(a,b) {
  		let i0 = a.getAttribute(orderAttr)?parseInt(a.getAttribute(orderAttr)):0,
  		    i1 = b.getAttribute(orderAttr)?parseInt(b.getAttribute(orderAttr)):0;
  		return i0 > i1?1:-1;
	});

        $items.each(function(i, e){
            e.replaceWith($cloned[i]);
	})
}

$('use[order]').click(function() {
    rebuildElementsOrder('use[order]', 'order');

    /* you can use z-index property for inline css declaration
    ** getComputedStyle always return "auto" in both Internal and External CSS decl [tested in chrome]
    
    rebuildElementsOrder( 'use[order]', null, function(a, b) {
        let i0 = a.style.zIndex?parseInt(a.style.zIndex):0,
  		    i1 = b.style.zIndex?parseInt(b.style.zIndex):0;
  		return i0 > i1?1:-1;
    });
    */
});
use[order] {
  cursor: pointer;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" id="keybContainer" viewBox="0 0 150 150" xml:space="preserve">
<defs>
    <symbol id="sym-cr" preserveAspectRatio="xMidYMid meet" viewBox="0 0 60 60">
        <circle cx="30" cy="30" r="30" />
        <text x="30" y="30" text-anchor="middle" font-size="0.45em" fill="white">
            <tspan dy="0.2em">Click to reorder</tspan>
        </text>
    </symbol>
</defs>
    <use order="1" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="0" y="0" width="60" height="60" style="fill: #ff9700; z-index: 1;"></use>
    <use order="4" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="50" y="20" width="50" height="50" style="fill: #0D47A1; z-index: 4;"></use>
    <use order="5" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="15" y="30" width="50" height="40" style="fill: #9E9E9E; z-index: 5;"></use>
    <use order="3" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="25" y="30" width="80" height="80" style="fill: #D1E163; z-index: 3;"></use>
    <use order="2" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="30" y="0" width="50" height="70" style="fill: #00BCD4; z-index: 2;"></use>
    <use order="0" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="5" y="5" width="100" height="100" style="fill: #E91E63; z-index: 0;"></use>
</svg>

Solution 16:[16]

A better example of use, that I've ended up using.

<svg>
  <defs>
    <circle id="one" fill="green" cx="40" cy="40" r="20" /> 
    <circle id="two" fill="orange" cx="50" cy="40" r="20"/> 
  </defs>
  <use href="#two" />
  <use href="#one" />
</svg>

To control the order you can change href attribute values of these use elements. This can be useful for animation.

Thanks to defs, circle elements are drawn only once.

jsfiddle.net/7msv2w5d

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