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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11To capture a scrollable modal’s complete contents, render the element that actually scrolls and set html2canvas’s rendering window to that element’s scrollWidth and scrollHeight. In a typical dialog, that is the inner content panel, not the outer dialog shell:
const target = document.querySelector('.modal-body');
const canvas = await html2canvas(target, {
windowWidth: target.scrollWidth,
windowHeight: target.scrollHeight,
});If the result is still cut off, verify the scrolling element, distinguish window dimensions from canvas dimensions and scroll offsets, then check browser canvas limits, CSS support and cross-origin images.
Why a modal capture gets cut off
A modal often has several nested boxes: an overlay, dialog shell, header, body and footer. CSS commonly gives only the body overflow: auto and a constrained height. The browser viewport shows a slice of that body, so a normal html2canvas call reproduces the visible slice rather than the body’s complete scrollable extent.
html2canvas does not take a native screenshot of the already-composited tab. It reads the DOM and styles, then paints an image onto a canvas. The element you pass is therefore crucial: selecting the shell when the body owns the scrollbar can leave the content clipped or produce dimensions that do not describe the intended output.
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Identify the element that owns the scrollbar
Inspect the DOM, not the component name
Use browser developer tools and find the element whose scrollbar moves when you scroll the modal content. Check its scrollHeight and scrollWidth against clientHeight and clientWidth. A scrolling element normally has a larger scroll dimension than its client dimension.
const candidates = document.querySelectorAll('.modal, .modal *');
for (const el of candidates) {
if (el.scrollHeight > el.clientHeight || el.scrollWidth > el.clientWidth) {
console.log(el, {
scrollWidth: el.scrollWidth,
scrollHeight: el.scrollHeight,
clientWidth: el.clientWidth,
clientHeight: el.clientHeight,
});
}
}Class names such as .modal-body are only examples. Frameworks may use a differently named content pane, or the dialog itself may own the scrolling. Choose the smallest element that contains everything you need.
Decide whether chrome belongs in the image
If the screenshot should contain only the long content, capture the scrolling panel. If it must include a header, footer, backdrop or close button, capture an enclosing element and confirm that its scroll dimensions cover the complete composition. There is no universal selector that works for every modal layout.
The documented full-content fix
Basic capture
const target = document.querySelector('.modal-body');
if (!target) throw new Error('Scrollable modal content was not found');
const canvas = await html2canvas(target, {
windowWidth: target.scrollWidth,
windowHeight: target.scrollHeight,
});
document.body.appendChild(canvas);windowWidth and windowHeight define the virtual rendering window html2canvas uses while cloning and painting the page. Setting them to the target’s scroll dimensions lets the cloned render account for content that is outside the visible viewport.
Save the result as an image
const target = document.querySelector('.modal-body');
if (!target) throw new Error('Scrollable modal content was not found');
const canvas = await html2canvas(target, {
windowWidth: target.scrollWidth,
windowHeight: target.scrollHeight,
});
const link = document.createElement('a');
link.download = 'modal.png';
link.href = canvas.toDataURL('image/png');
link.click();For JPEG output, use canvas.toDataURL('image/jpeg', 0.9). PNG preserves text and transparency better; JPEG is usually smaller for photographic content.
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Include remote images when permitted
const target = document.querySelector('.modal-body');
if (!target) throw new Error('Scrollable modal content was not found');
const canvas = await html2canvas(target, {
windowWidth: target.scrollWidth,
windowHeight: target.scrollHeight,
useCORS: true,
});useCORS: true asks the browser to load cross-origin images with CORS. It succeeds only when each image server sends a suitable Access-Control-Allow-Origin header. The option cannot bypass the browser’s origin policy. If the server cannot provide permission, use a configured proxy or remove the image from the capture.
Dimensions, scroll positions and ignored elements
Do not confuse the size options
windowWidthandwindowHeight: the virtual window used during rendering. They can change responsive breakpoints and are the primary fix for content outside the visible viewport.widthandheight: the canvas dimensions. They control the output bitmap and are not interchangeable with the window dimensions.scrollXandscrollY: the scroll position used for rendering. They matter for fixed-position elements and for captures that intentionally start at an offset.
For a full modal body, start with the scroll-dimension window settings and leave offsets at their defaults. Add an explicit offset only when your layout or fixed controls require it.
Hide controls that should not appear
Add data-html2canvas-ignore to buttons, resize grips or other interface elements that should be excluded:
<button data-html2canvas-ignore>Close</button>The element remains visible in the live modal but is omitted from the rendered image.
Wait until the modal is complete
Measure dimensions after the dialog is open, fonts have loaded and asynchronous content has been inserted. Measuring a collapsed or still-loading panel gives html2canvas the wrong extent. A simple application-level sequence is:
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- Open the modal.
- Insert or fetch its content.
- Wait for the layout to settle (for example, after the relevant render callback).
- Read
scrollWidthandscrollHeight. - Call html2canvas with those values.
A robust reusable helper
async function captureScrollableModal(selector) {
const target = document.querySelector(selector);
if (!target) {
throw new Error(`Scrollable modal element not found: ${selector}`);
}
// Force layout before reading dimensions.
const width = target.scrollWidth;
const height = target.scrollHeight;
if (!width || !height) {
throw new Error('The target has no measurable scrollable area');
}
const canvas = await html2canvas(target, {
windowWidth: width,
windowHeight: height,
useCORS: true,
});
if (canvas.width !== width || canvas.height !== height) {
console.warn('Canvas dimensions differ from target dimensions', {
target: { width, height },
canvas: { width: canvas.width, height: canvas.height },
});
}
return canvas;
}
captureScrollableModal('.modal-body').then(canvas => {
const link = document.createElement('a');
link.download = 'modal.png';
link.href = canvas.toDataURL();
link.click();
});The dimension comparison is diagnostic rather than a guarantee: device-pixel settings, browser behavior and implementation details can affect the final bitmap.
When the dimension fix still fails
The target is still the wrong element
If the canvas height matches a short shell while the body remains clipped, the body owns scrolling and must be captured directly. Conversely, capturing only the body omits a header or footer that sits outside it. Recheck which scrollbar moves and compare the target’s measured dimensions with the intended image.
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Very large canvases can exceed browser or platform limits. Limits vary by browser and device, so no single maximum is a safe universal rule. Split exceptionally long content into smaller captures, reduce the rendered area, or use a native capture mechanism appropriate to your application.
Styles do not match the modal
html2canvas implements CSS properties individually and its CSS support is incomplete. Correct dimensions do not guarantee identical effects for every filter, blend mode, transform, pseudo-element or advanced layout feature. Isolate the affected style, check the project’s current support, and simplify or replace unsupported styling when exact visual fidelity matters.
Images taint the canvas or disappear
For remote images, use useCORS: true only when the image host grants permission. Otherwise configure a proxy, serve the assets from the same origin, or omit them. A browser policy cannot be defeated by a JavaScript flag.
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Fixed elements appear in an unexpected place
Fixed-position elements are rendered relative to the configured window and scroll position. Adjust scrollX or scrollY deliberately, and decide whether those controls should instead carry data-html2canvas-ignore.
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Performance and reliability considerations
Keep the capture area intentional
A full scroll height increases the number of pixels html2canvas must paint and encode. Capture the content panel rather than the entire page, hide irrelevant widgets, and avoid repeatedly capturing while the user is scrolling. Trigger a capture after content stabilizes.
Plan for long documents
For a modal that can grow to many screenfuls, test representative content on the browsers and devices you support. If a single bitmap approaches practical canvas limits, capture sections and stitch them in an image workflow, or use a browser-native screenshot facility when your environment provides one.
Understand what “screenshot” means here
html2canvas is a DOM reconstruction tool. It is useful when you need an element image inside a web application, but it is not equivalent to a browser tab screenshot. Browser extensions that need an actual tab image should use the browser’s native tab screenshot API, as recommended by the html2canvas FAQ.
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FAQ
Should I set the modal’s CSS height to its full scroll height?
Not necessarily. The documented approach changes html2canvas’s rendering window; altering live layout can affect responsive styling and the user experience. First select the correct scrolling element and pass its measured dimensions.
Can html2canvas capture content that is display:none?
Hidden content has no rendered layout to measure or paint. Make the modal and its content renderable, wait for layout, then capture it.
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Why does a native tab screenshot differ from html2canvas?
A native screenshot captures the browser’s composited pixels. html2canvas rebuilds the image from DOM nodes and supported CSS, so unsupported properties, cross-origin images and browser limits can produce differences.
Frequently Asked Questions
Does html2canvas automatically scroll through a modal?
No. It renders the target using its configured window. Set that window from the target’s scroll dimensions and ensure the target owns the scrolling.
What is the best output format for modal text?
PNG is usually the safest choice for text, UI edges and transparency. Use JPEG when smaller photographic output matters more than lossless text edges.
Can I capture only one component inside the modal?
Yes. Pass that component to html2canvas, provided its dimensions include all content you intend to render.
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