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Editorial Team
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Asked: 2026-05-26T08:53:32+00:00

I am developing in Chrome and Firefox and I’ve been having trouble with an

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I am developing in Chrome and Firefox and I’ve been having trouble with an SVG filter. when applied to a rect it seems to affect more than just the <rect> element. Below is a screenshot of the result. As you can see it shades outside of the <rect> which is undesired.

Below is the result in Chrome:
undesired result in Chrome

Below is the result in Firefox:
undesired result in FF

<?xml version="1.0" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head></head>
<body>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" baseProfile="full" width="100%" height="100%">
<defs>
<filter id="dropshadow" height="130%">
<feGaussianBlur in="SourceAlpha" stdDeviation="10"/> 
<feOffset dx="5" dy="5" result="offsetblur"/>
<feMerge> 
<feMergeNode/>
<feMergeNode in="SourceGraphic"/> 
</feMerge>

<filter id = "I">
<feSpecularLighting specularExponent="2" lighting-color="#F3F4F3">
<fePointLight x="300" y="100" z="100"/>
</feSpecularLighting>
</filter>
</filter>
</defs>

<rect x="33%" y="33%" rx="30" ry="30" width="33%" height="300px" style="fill:#FFFFFF; filter:url(#I)"></rect>

</svg>
</body>
</html>
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1 Answer

  1. Editorial Team

    This happens because the default filter effects region, as defined by the x, y, width and height parameters on the <filter> element, is 120% of the bounding box of the filtered element, not 100%.

    The specification clarifies:

    It is often necessary to provide padding space because the filter effect might impact bits slightly outside the tight-fitting bounding box on a given object. For these purposes, it is possible to provide negative percentage values for ‘x’ and ‘y’, and percentages values greater than 100% for ‘width’ and ‘height’. This, for example, is why the defaults for the filter effects region are x=”-10%” y=”-10%” width=”120%” height=”120%”.

    Changing this to 100% would still affect the entire bounding box, though, so including the areas outside the rounded corners of the <rect>. If you want to limit it to just the rectangle, you can use feComposite. E.g.

    <filter id="I">
    <feSpecularLighting specularExponent="2" lighting-color="#F3F4F3" result="light">
        <fePointLight x="300" y="100" z="100"/>
    </feSpecularLighting>
    <feComposite in="light" in2="SourceAlpha" operator="in" result="lit"/>
</filter>

    Also, you’ve nested the #I filter inside the #dropshadow filter. That’s not something you can do. Are you trying to combine the lighting and drop shadow? If so, you could do that like this:

    <filter id="dropshadow">
    <feSpecularLighting specularExponent="2" lighting-color="#F3F4F3" result="light">
        <fePointLight x="300" y="100" z="100"/>
    </feSpecularLighting>
    <!-- Apply lighting inside rectangle -->
    <feComposite in="light" in2="SourceAlpha" operator="in" result="lit"/>

    <feGaussianBlur in="SourceAlpha" stdDeviation="10"/>
    <feOffset dx="5" dy="5" result="blur"/>
    <!-- Apply blur outside rectangle -->
    <feComposite in="blur" in2="SourceAlpha" operator="out" result="shadow"/>

    <!-- Combine lighting and shadow -->
    <feComposite in="shadow" in2="lit" operator="xor" />
</filter>

    This doesn’t seem to work to work in Firefox, though, but then your original example doesn’t work in Firefox for me either.

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