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This method is useful for a user-selected card, report, invoice, or other region already displayed in your page. It is not a pixel-perfect browser screenshot: html2canvas reconstructs the image from DOM and CSS information, so cross-origin assets, iframes, unsupported CSS, and very large canvases need special handling.
Complete browser example
Install the package in the application that owns the page:
npm install @html2canvas/html2canvasGive the target an identifiable element and a button:
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<section id="receipt">
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</section>
<button id="upload" type="button">Upload screenshot</button>The following module captures that section at the device-pixel ratio, creates a PNG Blob, and uploads it as the multipart field screenshot:
import html2canvas from '@html2canvas/html2canvas';
function canvasToBlob(canvas, type = 'image/png', quality) {
return new Promise((resolve, reject) => {
canvas.toBlob(blob => {
if (blob) resolve(blob);
else reject(new Error('Canvas conversion failed'));
}, type, quality);
});
}
export async function captureAndUpload(element, endpoint) {
const canvas = await html2canvas(element, {
scale: window.devicePixelRatio,
useCORS: true
});
const blob = await canvasToBlob(canvas, 'image/png');
const formData = new FormData();
formData.append('screenshot', blob, 'screenshot.png');
const response = await fetch(endpoint, {
method: 'POST',
body: formData
});
if (!response.ok) throw new Error(`Upload failed: ${response.status}`);
return response;
}
document.querySelector('#upload').addEventListener('click', async () => {
const button = document.querySelector('#upload');
button.disabled = true;
try {
await captureAndUpload(document.querySelector('#receipt'), '/upload');
alert('Uploaded');
} catch (error) {
console.error(error);
alert(error.message);
} finally {
button.disabled = false;
}
});The /upload URL and response format belong to your application. Your server must parse multipart form data, authenticate the request, validate the declared and detected type, enforce a size limit, and choose a storage and retention policy.
How each stage works
1. Render a DOM region
html2canvas(element) returns a Promise that resolves to a canvas. Pass the exact element whose visible content you want. The library builds a representation from DOM information; it does not ask the browser for the same native bitmap produced by an operating-system screenshot.
2. Choose scale and output type
scale: window.devicePixelRatio preserves detail on high-density displays, but increases pixel count, memory use, conversion time, and upload size. A fixed value such as 1 is safer for large reports. toBlob() is asynchronous and uses PNG when no supported type is supplied. PNG is lossless and handles text and transparency well. JPEG can be smaller for photographic content:
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const jpeg = await canvasToBlob(canvas, 'image/jpeg', 0.85);
formData.append('screenshot', jpeg, 'screenshot.jpg');A null Blob indicates conversion failure. A canvas that contains disallowed cross-origin pixels can also make toBlob() raise a security error.
3. Build multipart data
FormData.append(name, blob, filename) supplies a normal file part. Add ordinary fields when needed:
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formData.append('screenId', 'receipt-1842');
formData.append('capturedAt', new Date().toISOString());Do not add Content-Type: multipart/form-data to the fetch headers. The browser generates the boundary and the complete header when it sees a FormData body. Manually supplying the header commonly produces an unparsable request.
4. Check the response
Fetch resolves even for HTTP errors, so check response.ok (or explicitly accept the statuses your API uses). Return JSON, an upload ID, or a storage URL according to your endpoint contract.
Capture variations
Selected rectangle
When you need a crop rather than an element, render the relevant container or use the library’s position and size options. Supply x, y, width, and height in CSS pixels. Ensure the coordinates describe the same viewport and scroll position used for the render.
Full-page content
For a long page, set windowWidth and windowHeight to the document or target’s scroll dimensions and capture an element containing the full content. A full-page canvas can exceed browser dimension or area limits; split the page into sections or reduce scale when the output is blank, clipped, or partially rendered.
const target = document.documentElement;
const canvas = await html2canvas(target, {
windowWidth: target.scrollWidth,
windowHeight: target.scrollHeight,
scale: 1,
useCORS: true
});Wait for content before rendering
Capture only after fonts, images, and application data needed by the target are ready. In an SPA, wait for the component’s loaded state rather than taking the screenshot immediately after navigation. A short application-controlled delay can help animations settle, but waiting for an explicit selector or state is more deterministic.
Hide controls or mark a capture state
Use a capture-specific class to hide buttons, focus rings, and transient UI, then remove it in a finally block:
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target.classList.add('capture-mode');
try {
const canvas = await html2canvas(target);
// convert and upload canvas here
} finally {
target.classList.remove('capture-mode');
}Cross-origin images, fonts, and iframes
Images and canvas tainting
Set useCORS: true only when the image server sends a suitable Access-Control-Allow-Origin response. The option cannot override a server’s policy. If the asset is not permitted, it may be omitted or taint the canvas, preventing safe export. A same-origin proxy that fetches the asset server-side and serves it from your origin is the usual remedy; configure that proxy with authentication, allow-lists, size limits, and content validation.
Cross-origin iframes
An iframe from another origin exposes no readable contentDocument to the parent page, so html2canvas cannot render its contents. Capture the iframe application from within its own origin, obtain an image from its owner, or use a real browser capture service instead.
CSS fidelity
Because the output is reconstructed, some browser effects, generated content, filters, plugins, video frames, and unsupported CSS can differ from what a user sees. Compare the result at the viewport and browser versions that matter to your application rather than assuming pixel identity.
Browser API and extension alternatives
Native visible-tab capture
A browser extension can use chrome.tabs.captureVisibleTab() or browser.tabs.captureVisibleTab(). This captures the visible tab through the extension platform, not a DOM reconstruction. It requires an extension manifest, the relevant permissions, an active tab, and an extension deployment model, so it is inappropriate for an ordinary web page without those privileges.
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Puppeteer or Playwright run a real browser outside the page and are better when you need browser-level rendering, authenticated navigation, full-page screenshots, or server-side jobs. html2canvas depends on browser APIs and is not a Node.js server renderer by itself. Headless jobs require browser binaries, concurrency limits, timeouts, sandboxing, and a policy for pages that contain untrusted content.
Upload endpoint checklist
- Require authentication and authorize the user or tenant that owns the destination.
- Parse multipart data with a maintained server library; never trust the filename or MIME type alone.
- Apply request, part, and decompressed-image size limits before storing.
- Decode the image to verify its format and reject unexpected content.
- Generate a server-side object key instead of using a user-supplied filename as a path.
- Set retention, access control, malware scanning, and deletion rules appropriate to the image.
- Return a clear 2xx response and a machine-readable error body for failures.
Troubleshooting blank, incomplete, or rejected screenshots
The screenshot is blank
- Check that the element is connected, visible, and has non-zero dimensions at capture time.
- Wait until asynchronous data and images have loaded.
- Reduce
scaleand the capture area if the canvas exceeds browser limits. - Inspect cross-origin images and remove or proxy assets that cannot provide CORS permission.
- Disable transitions or animations while capturing so the cloned state is stable.
Images are missing
Confirm that each image URL is reachable and that its response includes an appropriate Access-Control-Allow-Origin header when it is not same-origin. useCORS: true is necessary in that case but is not sufficient without server cooperation. Cross-origin iframe contents remain inaccessible.
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toBlob() returns null or throws SecurityError
The canvas may be non-origin-clean because a cross-origin resource was drawn without permission. Remove that resource, serve it through a controlled same-origin proxy, or capture with a browser-level tool. Also catch conversion errors and avoid proceeding with an empty upload.
The server says the multipart body is malformed
Remove any manually set Content-Type header and send the FormData object directly. Verify that the server’s multipart parser is enabled and that its field name matches screenshot.
The server returns 401, 403, 413, or 415
- 401/403: send the authentication mechanism your endpoint requires and verify origin and CSRF rules.
- 413: lower the pixel scale, choose JPEG where appropriate, or raise the server limit deliberately.
- 415: check the generated Blob type and the server’s accepted formats.
The upload succeeds but the image is wrong
Log the target’s dimensions, device-pixel ratio, scroll position, and application state at capture time. Compare an element capture with a smaller scale. If exact browser pixels, cross-origin frames, or video are mandatory, switch to extension or headless-browser capture.
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Keep work bounded
Large DOM trees and high device-pixel ratios consume main-thread time and memory. Capture only the required element, avoid duplicate captures, and release references after upload. For repeated work, queue requests and apply back-pressure rather than launching many renders simultaneously.
Make retries safe
Use an idempotency key or client-generated capture ID so a retry after a network timeout does not create duplicate records. Abort a fetch with an application timeout, but remember that cancelling the browser request does not necessarily cancel server-side processing already received.
Protect user data
Screenshots can contain personal, financial, or secret information. Tell users what is captured, redact sensitive fields before rendering where possible, use HTTPS, and avoid logging image bytes or signed URLs in ordinary application logs.
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Or skip the browser setup
ScreenshotNeo is a website screenshot API and MCP server when the target is a URL rather than an element inside your current page. One GET request returns PNG, JPEG, WebP, or PDF. Before capture it accepts cookie or consent banners and removes more than 60 known consent platforms, newsletter popups, and chat widgets; each step can be turned off. Bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and response headers identify the page verdict and billing result. Its MCP server exposes take_screenshot, get_page_info, and capture_pdf for Claude, Cursor, and other MCP clients.
See the complete parameter list in the ScreenshotNeo documentation. This cURL call captures a URL without installing a browser:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpThe equivalent Python request is:
import 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)And Node.js:
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
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Frequently Asked Questions
Can I upload a canvas directly with fetch?
Yes. Convert it with toBlob(), append the Blob to FormData, and send that FormData as the fetch body.
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Why does html2canvas differ from a browser screenshot?
It reconstructs the image from DOM and CSS rather than capturing the browser’s final pixels, so unsupported styling and inaccessible resources can differ.
Should screenshots be PNG or JPEG?
Use PNG for text, UI, and transparency. Use JPEG with a chosen quality when photographic content and smaller files matter.
Can html2canvas capture another site’s iframe?
No. Cross-origin iframe documents are inaccessible to the parent page.
Quick Recap
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