Use jsPDF to build the document, generate a temporary Blob URL, and pass that URL to window.open() from the same user action that started the operation. The essential pattern is:
import { jsPDF } from 'jspdf';
function openPdfPreview() {
const doc = new jsPDF();
doc.text('Hello world!', 10, 10);
const blobUrl = doc.output('bloburl');
const previewTab = window.open(blobUrl, '_blank');
if (!previewTab) {
console.warn('Allow popups or use the PDF download link.');
}
}Attach that function to a real button. A browser may block a tab opened after a long asynchronous operation, so the call to window.open() must remain tied to a user gesture. The generated PDF is normally displayed by the browser’s built-in PDF viewer, although exact behavior depends on browser settings, extensions and version.
What the jsPDF workflow does
There are four steps:
- Create a
jsPDFinstance and add content. - Ask jsPDF for a Blob URL with
output('bloburl'). - Open that URL in a new browsing context with
window.open(blobUrl, '_blank'). - Check the return value and provide a fallback if it is
null.
bloburl creates an object URL backed by URL.createObjectURL when available. It is temporary and remains usable until you revoke it or the document is unloaded.
Complete button-based example
Install jsPDF with your package manager:
npm install jspdfThen import it in your application and connect the handler to a button:
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import { jsPDF } from 'jspdf';
const previewButton = document.querySelector('#preview-pdf');
const fallback = document.querySelector('#pdf-fallback');
previewButton.addEventListener('click', () => {
const doc = new jsPDF({
orientation: 'portrait',
unit: 'mm',
format: 'a4'
});
doc.setFontSize(18);
doc.text('Invoice preview', 20, 25);
doc.setFontSize(11);
doc.text('Generated in the browser with jsPDF.', 20, 35);
const blobUrl = doc.output('bloburl');
const previewTab = window.open(blobUrl, '_blank', 'noopener');
if (!previewTab) {
fallback.hidden = false;
fallback.href = blobUrl;
fallback.textContent = 'Open the generated PDF';
previewButton.setAttribute('aria-describedby', 'popup-status');
document.querySelector('#popup-status').textContent =
'The browser blocked the preview tab. Use the PDF link below or allow popups for this site.';
} else {
previewTab.opener = null;
}
});Example markup:
<button id="preview-pdf" type="button">Preview PDF (opens in new tab)</button>
<p id="popup-status" role="status"></p>
<a id="pdf-fallback" hidden download="generated.pdf"></a>The noopener feature and clearing opener prevent the new page from retaining a scriptable reference to the opener. Keep the visible label explicit: users should know that activating the button changes browsing context.
Why window.open() returns null
Modern browsers apply strict popup policies. A new tab or window is generally allowed only when the call occurs directly inside a trusted user action such as a click. If your code waits for a timer, a network request, a large rendering task or another promise before opening the context, the browser can classify it as unsolicited and return null.
Open first when generation is asynchronous
If producing the PDF requires asynchronous work, open a blank context synchronously, then navigate it after the PDF is ready. This preserves the user gesture while still allowing asynchronous generation:
import { jsPDF } from 'jspdf';
async function buildPdfData() {
// Replace this with your asynchronous data loading.
const response = await fetch('/api/invoice');
const invoice = await response.json();
const doc = new jsPDF();
doc.text(`Invoice ${invoice.number}`, 20, 25);
doc.text(`Total: ${invoice.total}`, 20, 35);
return doc.output('bloburl');
}
document.querySelector('#async-preview').addEventListener('click', async () => {
const previewTab = window.open('', '_blank', 'noopener');
if (!previewTab) {
document.querySelector('#popup-status').textContent =
'The browser blocked the preview. Allow popups and try again.';
return;
}
previewTab.document.title = 'Preparing PDF preview';
previewTab.document.body.textContent = 'Preparing PDF…';
try {
const blobUrl = await buildPdfData();
previewTab.location.href = blobUrl;
} catch (error) {
previewTab.document.body.textContent = 'Could not generate the PDF.';
console.error(error);
}
});This blank-tab technique is a practical application of the documented user-gesture rule. Verify it in the browsers your application supports: popup handling, opener behavior and PDF viewers can vary.
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Managing the Blob URL lifecycle
jsPDF’s documentation states that the developer is responsible for calling revokeObjectURL. Do not revoke the URL immediately after window.open(); the PDF viewer may not have loaded it yet.
Simple cleanup
If the preview is short-lived, retain the URL and revoke it after a conservative delay:
const blobUrl = doc.output('bloburl');
const tab = window.open(blobUrl, '_blank', 'noopener');
if (tab) {
// Choose a delay appropriate to your application and document size.
setTimeout(() => URL.revokeObjectURL(blobUrl), 60_000);
}A timeout is only a basic policy; it cannot know when a user has finished reading. For longer-lived previews, keep the URL in application state and revoke it when the preview component is closed or unmounted. If you revoke too early, the viewer can show a blank page or a load error.
Creating the URL yourself from a Blob
Use output('blob') when you need explicit control:
const pdfBlob = doc.output('blob');
const blobUrl = URL.createObjectURL(pdfBlob);
const tab = window.open(blobUrl, '_blank', 'noopener');
if (!tab) {
const link = document.createElement('a');
link.href = blobUrl;
link.download = 'generated.pdf';
link.textContent = 'Download generated PDF';
document.body.append(link);
}Revoke this URL using the same lifecycle rules. A Blob URL is not a permanent public address and normally cannot be shared with another user or server.
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Preview versus download: choose the right jsPDF output
| Method | Result | Best use | Important caveat |
|---|---|---|---|
output('bloburl') or output('bloburi') |
Temporary URL for the generated PDF | Open a browser preview with window.open() |
You must eventually revoke the object URL |
output('dataurlnewwindow') |
Asks jsPDF to open a window containing an iframe with a data URL | Quick browser-only preview | Still subject to popup blocking |
output('blob') |
A Blob object |
Custom URL, upload or download workflow | You manage the object URL if you create one |
save('generated.pdf') |
Downloads the file | Explicit download action | It is not a preview; jsPDF documents it as an alias of output('save', filename) using FileSaver.js |
output('pdfjsnewwindow') |
Opens a PDF.js-based viewer route | Applications that have configured the required PDF.js viewer path | Not a universally configured default |
For a normal inline browser preview, bloburl gives the clearest control over popup failure, fallback links and cleanup.
Handling popup failure accessibly
- Always test the return value from
window.open(). - Show a normal link or download control if it is
null. - Use a live status region such as
role="status"to explain what happened. - Label the activating control “Preview PDF (opens in new tab)” rather than disguising an action as
href="#". - Use a separate user gesture for each tab you open; browsers can reject multiple popups from one click.
A successful call does not guarantee the same visual result everywhere. Browser PDF preferences, extensions and built-in viewers determine whether the file appears inline, downloads automatically or is handed to another application.
Troubleshooting
The new tab is blocked
Cause: the call happened after asynchronous work, in a timer, or outside a trusted click. Fix: move window.open() into the click handler, or open a blank tab first and navigate it after generation. Check for a null return and provide a link.
The tab opens but is blank
Cause: the object URL was revoked too soon, PDF generation failed, or the browser viewer rejected the data. Fix: delay revocation, catch generation errors, inspect the Blob, and try the explicit output('blob') plus URL.createObjectURL route.
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The file downloads instead of displaying
Cause: browser preferences, extensions or response handling choose download behavior. Fix: you cannot force identical inline handling across every browser; offer the download as an intentional fallback and test target browser policies.
Characters or fonts are wrong
Cause: the PDF uses jsPDF’s default fonts, which do not cover every writing system. Fix: embed a compatible font in jsPDF and verify the resulting document in the viewers your users rely on.
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Cause: application data was read before the latest edit completed. Fix: snapshot the form or fetched data inside the click handler, then generate from that snapshot.
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Or skip the browser setup
If your actual goal is capturing an existing website rather than constructing a PDF with jsPDF, ScreenshotNeo provides a one-request screenshot API and an MCP server for AI agents. It accepts consent banners before capture and removes more than 60 known consent platforms, newsletter popups and chat widgets. Bot checks, blank pages, timeouts, failed loads and cache hits are not billed, and response headers identify the page verdict and billing result.
cURL:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpPython:
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)Node.js:
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Practical checklist
- Generate the PDF inside a click or other trusted user action.
- Use
output('bloburl')for a straightforward preview. - Check for
nullfromwindow.open(). - Show a visible link or download fallback.
- Keep the Blob URL alive until loading is likely complete, then revoke it.
- Test popup, viewer and download behavior in your supported browsers.
Frequently Asked Questions
Can I open a jsPDF file without saving it first?
Yes. Generate a Blob URL with doc.output('bloburl') and open that URL; no intermediate file needs to be written to disk.
Does opening a PDF in a new tab always work on mobile?
No universal guarantee exists. Browser settings, built-in viewers and extensions can change whether a new tab opens or the PDF downloads.
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Should I use dataurlnewwindow instead?
It is a documented browser route, but it still depends on popup permission. The Blob URL approach gives you clearer control over fallback handling and URL cleanup.
Quick Recap
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