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Use filter: drop-shadow() when a transparent PNG’s shadow should follow the visible artwork. Use box-shadow when you want a shadow around the image element’s rectangular box. These properties produce different geometry, so choosing the right one matters more than changing blur or color.
Use drop-shadow() for a transparent PNG silhouette
A PNG can contain transparent pixels around a logo, icon, product cutout, or irregular illustration. The CSS drop-shadow() filter reads the rendered image’s alpha mask and places a blurred, offset copy beneath the visible pixels.
<img class="logo" src="logo.png" alt="Company logo">.logo {
filter: drop-shadow(4px 6px 8px rgb(0 0 0 / 0.35));
}The first length moves the shadow horizontally; the second moves it vertically. Positive values move right and down, while negative values move left and up. The optional third length controls blur. The color can appear before or after the lengths. If you omit the color, the filter uses the element’s color value. See MDN’s drop-shadow() reference.
A sharp or unblurred shadow
Omit the blur length, or set it to zero, when you want a crisp offset edge.
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.icon {
filter: drop-shadow(3px 3px 0 rgb(0 0 0 / 0.45));
}This is useful for pixel-art effects, stickers, and small icons where a large blur can make the result muddy.
A soft shadow with explicit opacity
.product-cutout {
filter: drop-shadow(0 12px 18px rgb(0 0 0 / 0.22));
}An explicit color and alpha value makes the result predictable against different backgrounds. A semi-transparent black is a common starting point, but a tinted shadow can better match a colored interface.
Use box-shadow for the image element’s rectangle
box-shadow shadows the element’s box, not the non-transparent portions of the file. It is therefore appropriate for a rectangular photograph, a framed preview, or a card containing an image.
.preview {
box-shadow: 0 8px 20px rgb(0 0 0 / 0.2);
}Applied directly to an irregular transparent PNG, this creates a rectangular shadow that includes empty transparent space. If that is not the intended appearance, switch to filter: drop-shadow().
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drop-shadow() versus box-shadow
| Feature | filter: drop-shadow() |
box-shadow |
|---|---|---|
| Shadow shape | Follows the rendered PNG alpha mask | Follows the element’s rectangular box |
| Required geometry | Horizontal and vertical offsets | Horizontal and vertical offsets |
| Blur | Optional third length | Optional blur radius |
| Spread | Not supported | Optional spread radius |
| Inset effect | Not supported | Supports the inset keyword |
| Multiple shadows | Repeat drop-shadow() functions in one filter list |
Separate shadows with commas |
MDN documents the available box-shadow values, while the W3C describes one or more shadows attached to a box in the CSS Backgrounds and Borders Module Level 3.
Build layered shadows
For a stronger edge plus a softer falloff, repeat the filter function in a space-separated list.
.logo {
filter: drop-shadow(2px 3px 3px rgb(0 0 0 / 0.35))
drop-shadow(0 0 1px rgb(0 0 0 / 0.2));
}Functions run in the order written. Inspect the complete list when another filter, such as brightness() or grayscale(), changes the appearance. Filter effects are covered in MDN’s Using filter effects guide.
Control the effect with custom properties
Custom properties make one shadow recipe reusable across themes and component sizes.
:root {
--png-shadow-x: 0px;
--png-shadow-y: 8px;
--png-shadow-blur: 16px;
--png-shadow-color: rgb(0 0 0 / 0.24);
}
.hero-art {
filter: drop-shadow(
var(--png-shadow-x)
var(--png-shadow-y)
var(--png-shadow-blur)
var(--png-shadow-color)
);
}
[data-theme="dark"] {
--png-shadow-color: rgb(0 0 0 / 0.55);
}Keep the alpha channel modest on busy backgrounds. A very dark shadow can reduce nearby text contrast even when the image itself is decorative.
Complete responsive example
This example uses drop-shadow() for a transparent product cutout and changes only the offset and blur at a wider viewport.
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<figure class="product-figure">
<img
class="product-figure__image"
src="headphones.png"
alt="Black wireless headphones"
width="800"
height="600"
>
<figcaption>Wireless headphones</figcaption>
</figure>.product-figure {
max-width: 32rem;
margin: 2rem auto;
text-align: center;
}
.product-figure__image {
display: block;
width: min(100%, 800px);
height: auto;
filter: drop-shadow(0 8px 12px rgb(0 0 0 / 0.24));
}
@media (min-width: 48rem) {
.product-figure__image {
filter: drop-shadow(0 16px 24px rgb(0 0 0 / 0.22));
}
}Declaring intrinsic width and height helps the browser reserve layout space while the PNG loads. display: block removes the default inline-image baseline gap; it does not affect the shadow geometry.
What drop-shadow() cannot do
- There is no
spreadvalue in the function. To imitate a thicker outline, stack another low-blur shadow or edit the source artwork. - There is no
insetkeyword. An inner shadow requires a different technique, such as a clipped pseudo-element or an SVG effect. - The shadow follows the pixels the browser renders. Transparent padding in the file does not become an opaque rectangle, but semi-transparent pixels can produce correspondingly soft edges.
Fix clipping, overrides, and unexpected geometry
The shadow is rectangular
Check the computed style and replace box-shadow with filter: drop-shadow(...) when the visible silhouette is the desired outline.
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The shadow is too hard or too soft
Change the third length in drop-shadow(). Lower values sharpen the edge; higher values spread the blur. Adjust opacity separately so you do not use blur to compensate for an overly dark color.
The shadow is on the wrong side
Verify the signs of both offsets. For example, drop-shadow(-6px -4px 8px ...) moves the effect left and upward.
The shadow is invisible
- Set an explicit color such as
rgb(0 0 0 / 0.3). - Inspect the browser’s computed styles for a later rule that resets
filtertonone. - Check whether another filter list replaces the entire declaration. CSS does not merge separate
filterdeclarations; the winning declaration supplies the complete list.
The shadow is clipped
Blurred and offset pixels can extend outside the image’s box. An ancestor with overflow: hidden or another constrained clipping region may cut them off. Remove or relax that constraint where possible, or provide surrounding layout space. The required space depends on the offsets and blur, so verify it at the largest rendered size rather than choosing a universal margin.
Accessibility, rendering, and browser support
Shadow is decoration and should not replace meaningful contrast, labels, or focus indicators. Keep useful alternative text on informative images and use an empty alt attribute for purely decorative PNGs.
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Or skip the browser setup:
If your goal is to obtain a clean rendered image after applying your CSS, ScreenshotNeo can capture the page through one HTTP request. It accepts cookie and consent banners like a visitor, then removes more than 60 known consent platforms, newsletter popups, and chat widgets; each cleanup step can be disabled. Only clean shots are billed: bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits cost nothing, and the response reports the result through X-Page-Verdict and X-Billed headers.
The API supports PNG, JPEG, WebP, and PDF output, full-page captures with lazy images loaded, CSS-selector element captures, dark mode, device presets, arbitrary viewports, retina scale, custom CSS and JavaScript, clicks, waits, blocked requests, custom headers and cookies, user agents, authorization, timezone and geolocation, transparent backgrounds, resizing, selectable cache TTLs, signed image links, asynchronous jobs with signed webhooks, bulk capture of up to 100 URLs per call, a usage API, and an OpenAPI specification. Its parameter names are compatible with those used by other screenshot APIs, which can simplify migration.
Use the ScreenshotNeo documentation for the complete option list. Here are runnable requests for a page containing the PNG shadow:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpimport requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);ScreenshotNeo includes an MCP server with take_screenshot, get_page_info, and capture_pdf tools for Claude, Cursor, and other MCP clients. The Free plan includes 1,000 shots per month with no card; paid plans start at $5 for 3,000 shots. Create a free ScreenshotNeo account to try it.
Quick decision checklist
- Choose
drop-shadow()when the shadow must follow transparent artwork. - Choose
box-shadowwhen the rectangular image or card frame should cast the shadow. - Use two offsets, then tune blur and opacity.
- Stack filter functions for layered effects, remembering that order matters.
- Inspect clipping ancestors and competing
filterdeclarations when the result is missing or cut off.
Frequently Asked Questions
Can I use both box-shadow and drop-shadow() on one PNG?
Yes. They are independent effects, so you can combine them when you intentionally want both a silhouette shadow and a rectangular frame shadow. Check the result at the image’s real size to avoid an overly heavy edge.
Which value moves a shadow upward?
Use a negative vertical offset, such as drop-shadow(0 -6px 10px rgb(0 0 0 / 0.3)). The second length is the vertical offset.
Does a PNG need to be edited before using CSS shadows?
No. A transparent PNG can be shadowed directly in CSS. The browser derives the silhouette from the rendered alpha channel.
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A later filter declaration replaces the earlier declaration rather than appending to it. Put all required functions in one winning filter list.
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