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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Use jQuery for the click handler and element lookup, then wait for html2canvas’s Promise before creating and saving the jsPDF file. The critical sequence is: unwrap the jQuery collection with [0], await html2canvas(), convert the resulting canvas with toDataURL(), place that image in jsPDF, and call save() only after rendering has completed.
The working pattern
Assume your page contains an element with id="content" and a button with id="savePdf". This handler combines jQuery and the two rendering libraries without racing the browser:
$('#savePdf').on('click', async function () {
const target = $('#content')[0];
if (!target) {
alert('The content element was not found.');
return;
}
try {
const canvas = await html2canvas(target, {
scale: window.devicePixelRatio,
useCORS: true
});
if (!canvas.width || !canvas.height) {
throw new Error('html2canvas returned an empty canvas.');
}
const imgData = canvas.toDataURL('image/png');
const pdf = new jsPDF({ unit: 'pt', format: 'a4', orientation: 'portrait' });
const pageWidth = pdf.internal.pageSize.getWidth();
const pageHeight = pdf.internal.pageSize.getHeight();
const ratio = Math.min(pageWidth / canvas.width, pageHeight / canvas.height);
const imageWidth = canvas.width * ratio;
const imageHeight = canvas.height * ratio;
pdf.addImage(imgData, 'PNG', 0, 0, imageWidth, imageHeight);
pdf.save('export.pdf');
} catch (error) {
console.error('PDF export failed:', error);
alert('Could not create the PDF. Check the console for details.');
}
});html2canvas documents that its function returns a Promise resolving to a <canvas> element (official getting-started documentation). Therefore, calling pdf.save() immediately after starting html2canvas can produce an empty or incomplete file.
Why the jQuery collection must be unwrapped
$('#content') is a jQuery collection, even when it contains one element. html2canvas expects the underlying DOM node. Use $('#content')[0] or $('#content').get(0):
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const target = $('#content')[0];
const canvas = await html2canvas(target);Passing the collection itself can result in a type error or no useful render. Check that the result is not undefined when the selector does not match anything.
What happens in each stage
- Event binding: jQuery listens for the button’s click.
- Element lookup: jQuery finds the content and
[0]extracts its DOM element. - DOM reconstruction: html2canvas reads the element and draws a visual representation into a canvas. It does not take a native operating-system screenshot; it recreates the page from DOM and CSS (project documentation).
- Promise completion:
awaitpauses the handler until the canvas is ready. - Image serialization:
canvas.toDataURL('image/png')creates the image payload. - PDF placement: jsPDF inserts that image and writes the file.
- Download:
pdf.save()starts the browser download only after all previous work succeeds.
Promise syntax without async/await
If your codebase uses callbacks, put every PDF operation inside .then(). This is the same ordering as the async version:
$('#savePdf').on('click', function () {
const target = $('#content')[0];
if (!target) {
alert('The content element was not found.');
return;
}
html2canvas(target, { useCORS: true })
.then(function (canvas) {
if (!canvas.width || !canvas.height) {
throw new Error('The canvas is empty.');
}
const pdf = new jsPDF('p', 'pt', 'a4');
const pageWidth = pdf.internal.pageSize.getWidth();
const scale = pageWidth / canvas.width;
pdf.addImage(
canvas.toDataURL('image/png'),
'PNG',
0,
0,
canvas.width * scale,
canvas.height * scale
);
pdf.save('export.pdf');
})
.catch(function (error) {
console.error('PDF export failed:', error);
alert('Could not create the PDF.');
});
});Fit the image to a page correctly
A canvas can be much wider or taller than an A4 page. Calculate one ratio and apply it to both dimensions so the image is not distorted:
const margin = 24;
const availableWidth = pageWidth - margin * 2;
const availableHeight = pageHeight - margin * 2;
const ratio = Math.min(
availableWidth / canvas.width,
availableHeight / canvas.height
);
pdf.addImage(
imgData,
'PNG',
margin,
margin,
canvas.width * ratio,
canvas.height * ratio
);If the content is taller than one page, fitting it onto a single page can make text unreadably small. Render separate sections, or slice the canvas into page-sized portions and call pdf.addPage() for each slice. Test page breaks with the real content; a visual image PDF has no automatic understanding of paragraphs, tables, or headings.
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Useful html2canvas options
| Option | Purpose | Important limitation |
|---|---|---|
scale |
Controls canvas resolution. window.devicePixelRatio usually improves sharpness on high-DPI screens. |
Higher values increase memory use, render time, and output size. |
useCORS: true |
Attempts to load cross-origin images with CORS. | It works only when the image server sends permissive CORS headers; it cannot bypass browser security. |
data-html2canvas-ignore |
Marks controls, ads, or other elements to exclude. | Add the attribute to each element you do not want rendered. |
For example:
<button id="savePdf" data-html2canvas-ignore>Save PDF</button>Make the captured state deterministic
- Wait until fonts, charts, and asynchronous data have finished before starting the export. A short application-level wait or a “ready” state is more reliable than an arbitrary delay.
- Temporarily open collapsed panels or remove hover-only styling if those states must appear in the PDF.
- Use a print-specific class to hide navigation and interactive controls, then remove it in a
finallyblock. - Keep the target visible and attached to the document. Elements with
display: nonehave no layout for html2canvas to reproduce.
Cross-origin images and canvas tainting
Images loaded from another origin can taint the canvas. When that happens, toDataURL() may throw a security exception or the image may be omitted. Prefer same-origin assets, configure the image server to send an appropriate Access-Control-Allow-Origin header, and use useCORS: true. A proxy under your control can relay assets when policy permits. Do not treat useCORS as a way to defeat cross-origin restrictions.
Visual PDF, not native PDF text
This workflow places a raster image in the PDF. The result preserves the appearance of the page, but text generally is not selectable as native PDF text and the document is not automatically accessible to screen readers. If searchable, selectable text or semantic accessibility is a requirement, generate a structured PDF instead of relying solely on a canvas image.
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html2canvas plus jsPDF versus html2pdf.js
Manual html2canvas and jsPDF code gives you direct control over page dimensions, margins, image placement, and custom page slicing. It is a good fit for a single dashboard, invoice, or controlled panel.
html2pdf.js wraps the same general workflow in a chain: .from() -> .toContainer() -> .toCanvas() -> .toImg() -> .toPdf() -> .save(). Its options can reduce boilerplate and help with page-break handling, but you still need to test long layouts, unsupported CSS, fonts, and cross-origin assets. Both approaches inherit browser same-origin and canvas-taint restrictions.
Performance, reliability, and cost considerations
- Memory: canvas memory grows with pixel dimensions. A large full-page element at a high
scalecan exceed mobile-device limits. - Speed: simplify expensive effects, capture only the required element, and avoid needlessly large images.
- Repeat clicks: disable the button while rendering and re-enable it in
finallyto prevent duplicate downloads. - Validation: check canvas dimensions before calculating ratios, and log the original error so failures are diagnosable.
- Browser behavior: downloads can be blocked when triggered outside a user gesture. Keep the initial call in the click handler; asynchronous work started from that handler normally retains the intended interaction.
Common failures and fixes
“Cannot read properties of undefined”
The selector matched nothing, so $('#content')[0] is undefined. Verify the ID, run the handler after the DOM exists, and check the element before calling html2canvas.
The PDF downloads before the page is rendered
pdf.save() is outside the Promise callback or follows an un-awaited call. Move all PDF code into await html2canvas(...), .then(), or a function that returns the Promise.
Images are missing or toDataURL() throws
Inspect cross-origin assets. Serve them from the same origin or configure CORS on the image host; then enable useCORS. A browser policy cannot be bypassed in JavaScript.
The output is blank
Capture only after the target has dimensions and visible content. Check for display:none, zero width or height, a failed data request, or a canvas size that exceeds device limits.
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The PDF is one tiny page
Your entire tall canvas was scaled to fit one sheet. Slice the canvas into multiple pages or capture logical sections separately.
Styles look different
html2canvas supports a DOM/CSS subset, not every browser feature. Replace unsupported effects for the export state, wait for web fonts, and test the exact browsers your users run.
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FAQ
Can I pass a jQuery object directly to html2canvas?
No. Pass the DOM node extracted with [0] or .get(0).
Does this produce a searchable PDF?
Not usually. The workflow embeds a rendered image, so text is generally not native PDF text.
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Will useCORS load every remote image?
No. The remote server must explicitly permit the request with CORS headers.
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Capture sections separately or slice the canvas across multiple PDF pages rather than shrinking the complete canvas onto one sheet.
Frequently Asked Questions
Can I pass a jQuery object directly to html2canvas?
No. Pass the DOM node extracted with [0] or .get(0).
Does this produce a searchable PDF?
Not usually. The workflow embeds a rendered image, so text is generally not native PDF text.
Will useCORS load every remote image?
No. The remote server must explicitly permit the request with CORS headers.
How should I export a very long page?
Capture sections separately or slice the canvas across multiple PDF pages rather than shrinking the complete canvas onto one sheet.
Quick Recap
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