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If html2canvas turns a rounded element into a rectangle, the cause is usually a mismatch in its DOM/CSS reconstruction rather than missing border-radius support. Confirm your installed version and browser, reproduce the problem with one simple element, then add styles back gradually. Test the documented foreignObjectRendering mode, inspect the cloned document with onclone, and isolate shadows or other effects before filing a minimal issue.
html2canvas does not copy the browser’s final pixels. It reads the DOM and CSS and builds a canvas representation, so a page that looks correct in the browser can render differently. The project lists border-radius as supported, but explains that every CSS property is implemented individually and coverage is not complete. See the html2canvas documentation and FAQ.
Why rounded corners become rectangles
There is no universal one-line fix. A radius can fail because of an html2canvas version difference, an interaction with shadows, transforms, borders, clipping or nested elements, or a browser-specific limitation in the renderer. The maintainers’ own guidance is to test the latest release with a reproducible case rather than assume that a CSS feature behaves exactly like native browser painting.
The FAQ states: “Every CSS property must be manually implemented to render correctly, so html2canvas will never have full CSS support.” That limitation explains why a valid CSS declaration can still produce a different canvas image.
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1. Record the exact capture context
Before changing code, write down the values that can change the result:
- The html2canvas version resolved by your package lockfile or script tag.
- Browser name and full version, operating system, and whether the page runs locally or on a deployed origin.
- The element’s width and height, computed
border-radius, border width, overflow, transform and stacking context. - Whether a
box-shadow, image, pseudo-element, filter or nested rounded child is present. - The html2canvas options used and any console errors or warnings.
Do not infer the version from a previous upgrade attempt. Check the installed dependency or the actual non-minified build loaded by the page. The project changelog includes historical radius-related fixes, including handling values over 50% and a top-right radius correction, so version can matter without guaranteeing that an upgrade resolves your case. Review the changelog.
2. Reproduce the radius with one element
Start with a plain element, a solid fill and no effects. Render only that element. This tells you whether the failure is the radius itself or a style interaction.
<div id="card">Rounded test</div>
<script src="https://html2canvas.github.io/html2canvas/dist/html2canvas.min.js"></script>
<script>
const element = document.querySelector('#card');
html2canvas(element).then(canvas => document.body.appendChild(canvas));
</script>#card {
width: 240px;
height: 120px;
background: #4b78d1;
border-radius: 16px;
}If this test is rounded, restore your production styles one at a time: first the border, then overflow and children, then images, transforms and shadow. Capture after each change. The first addition that makes corners square identifies the interaction you need to work around.
Check computed values, not just stylesheet text
Open DevTools, select the element and inspect the Computed panel. Confirm that each corner has the expected value (for example, 16px or the intended percentage) and that a more specific rule has not overridden it. Also check that the element being passed to html2canvas is the rounded node, not an outer wrapper with square geometry.
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3. Compare the alternate renderer
The configuration reference documents foreignObjectRendering. It asks the browser to render HTML inside an SVG foreignObject when the browser supports that path; the default is false. It is a diagnostic comparison, not a guaranteed fix for this symptom.
const element = document.querySelector('#card');
const canvas = await html2canvas(element, {
foreignObjectRendering: true
});
document.body.appendChild(canvas);Run the same minimal case with the option off and on in the target browser. Compare both the corner shape and the console output. If the alternate path works, you have a practical browser-dependent workaround, but test the full page because fonts, external images and other resources can behave differently. The supported option and defaults are listed in the configuration reference and features page.
4. Inspect the cloned document with onclone
html2canvas clones the document before rendering. The onclone callback lets you inspect or modify that clone without changing the live page. Use it to verify that the cloned element still has the expected computed radius.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsconst canvas = await html2canvas(document.querySelector('#card'), {
onclone(clonedDocument) {
const clonedElement = clonedDocument.querySelector('#card');
if (clonedElement) {
console.log(getComputedStyle(clonedElement).borderRadius);
}
}
});
document.body.appendChild(canvas);If the clone reports a different value, look for styles that depend on a class, media query or ancestor that is absent in the clone. You can apply a temporary diagnostic rule in the callback, capture it, and remove the rule from your production code after identifying the cause. The callback is an inspection and controlled-test tool, not a radius-specific patch.
5. Separate shadows from corner geometry
A reported html2canvas issue describes a coarse black border when box-shadow is combined with rounded corners. In that report, removing the shadow removed the artifact while the radius remained. This is narrow evidence: a dark outline is not the same failure as genuinely square corners.
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To test the interaction, capture the element once with the shadow and once without it:
const element = document.querySelector('#card');
const withoutShadow = element.cloneNode(true);
withoutShadow.style.boxShadow = 'none';
withoutShadow.style.position = 'fixed';
withoutShadow.style.left = '-10000px';
document.body.appendChild(withoutShadow);
const canvas = await html2canvas(withoutShadow);
withoutShadow.remove();
document.body.appendChild(canvas);If only the shadowed version fails, consider a simpler shadow, a separate wrapper for the shadow, or a post-processing step. Do not claim that this issue explains every rectangular output. Read the original report at Issue #2953.
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6. Reintroduce difficult CSS deliberately
Once the plain radius works, test these features separately:
- Percentage radii: verify the element has the intended dimensions; percentages resolve against its box and can expose version-specific behavior.
- Unequal corners: test explicit values such as
16px 24px 8px 32pxinstead of the shorthand first. - Borders: compare no border, a uniform border and individual border widths.
- Overflow and children: add
overflow: hiddenand nested content after the outer shape is confirmed. - Transforms: capture an untransformed element, then add scale, rotation or 3D transforms.
- Images and pseudo-elements: verify that resources have loaded and that the visible corner is not painted by a child covering the parent.
This matrix prevents a workaround for one interaction from hiding the actual failing property.
7. Check browser support and make a useful issue
The project lists modern evergreen Chrome/Chromium, Firefox and Safari as supported browsers, but the available guidance does not identify one browser as the general cause of rectangular corners. Run the same minimal page in the browser versions you support and record differences.
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If the reduced case still fails, use the latest release and the non-minified build, preserve console output, and attach the smallest HTML/CSS, the expected browser view and the actual canvas. Include the html2canvas release, browser and version, operating system, element dimensions, radius values and any shadow or transform. The FAQ recommends creating a test case when a CSS property is missing or incomplete. Start with the getting-started guide and follow the project’s issue-template expectations.
Common symptoms and targeted fixes
| Symptom | Likely scope | What to try |
|---|---|---|
| Simple solid card is square | Version, browser path or incomplete property implementation | Verify version, reduce to the minimal case, compare foreignObjectRendering, then report it. |
| Only a dark outline appears | Possible shadow interaction | Remove box-shadow for one capture and compare; do not generalize the result. |
| Only the production component fails | Interaction with border, transform, child or pseudo-element | Add styles back one at a time and inspect the cloned computed style. |
| Different browsers disagree | Renderer or browser implementation difference | Record browser versions, test the alternate mode where supported, and choose a tested path for your users. |
Or skip the browser setup
If your goal is a reliable website image rather than debugging a client-side canvas, ScreenshotNeo captures the rendered page through an API. It accepts consent banners like a visitor and removes more than 60 known consent platforms, newsletter popups and chat widgets before capture. Bot checks, blank pages, timeouts, failed loads and cache hits are not billed, and response headers identify the page verdict and billing status. Its MCP server provides take_screenshot, get_page_info and capture_pdf tools for Claude, Cursor and other MCP clients.
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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)
r.raise_for_status()
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}`);
if (!res.ok) throw new Error(`HTTP ${res.status}`);
const buffer = Buffer.from(await res.arrayBuffer());
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FAQ
Does html2canvas support border-radius at all?
Yes. The feature list includes it, but support is property-by-property and does not promise identical output for every combination of values and effects.
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Should I always enable foreignObjectRendering?
No. It is an optional path that depends on browser support. Compare it with the default renderer on your actual target browsers and page.
Is a square corner proof that my CSS is invalid?
No. If the live browser view is rounded and computed styles show the expected radius, the discrepancy can be in html2canvas’s reconstruction or in an interaction with another style.
Frequently Asked Questions
Can changing the canvas scale fix rounded corners?
Scale affects output resolution, not whether html2canvas correctly reconstructs the radius. Diagnose the renderer and CSS interaction first.
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