If Html2Pdf.app returns a PDF that looks blank, first check that the request actually succeeded and that your code saved the response as binary bytes. Then verify that the renderer can reach the source page and its assets, and test whether the page needs more time or a different CSS media mode. A blank-looking file can come from the input, rendering conditions, or response handling—not one universal setting.
1. Check the response before treating it as a PDF
Html2Pdf.app documents a synchronous success response as PDF binary data. Check the HTTP status before writing the response body to a file; do not parse it as JSON or convert it to text. The API uses POST https://api.html2pdf.app/v1/generate and an X-API-Key header. Its documentation says conversions run in headless Chromium, providing support for modern HTML, CSS, and JavaScript (Html2Pdf.app documentation).
| Status | Documented meaning | What to do |
|---|---|---|
| 400 | Inaccessible source URL or invalid parameter | Check the URL, required html field, and option values before retrying. |
| 401 | Missing or invalid API key | Send a valid key in the X-API-Key header. |
| 403 | Account plan limit | Check the account limit; repeated retries will not correct a plan restriction. |
| 500 | Unhandled server error | Inspect the response and retry cautiously; the documentation does not specify a guaranteed recovery time. |
| 202 | Accepted/queued when using callBackUrl |
Wait for the callback result; this initial response is not the completed PDF. |
The documented error meanings and recommended responses are in the API reference. A non-success response may contain an error body, so saving every response with a .pdf extension can hide the real failure.
2. Confirm the renderer can access the page and its assets
The required html field accepts either raw HTML markup or a publicly reachable page URL. Html2Pdf.app’s troubleshooting guidance says to check that the source URL is public and that required CSS, fonts, and images are reachable by the renderer (Node.js guide; cURL guide).
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- For a URL: open it without relying on your logged-in browser session. Check whether redirects lead to a login screen or another inaccessible destination. These are practical checks of the documented public-reachability requirement, not separate service guarantees.
- For raw HTML: inspect linked stylesheets, fonts, and images. The markup may arrive while its externally hosted assets do not.
- For a minimal test: submit a small HTML document with inline text and styling. If it renders while the original does not, compare external dependencies and page-specific scripts.
Do not assume that because a URL loads on your machine it is available to the rendering service; your browser may have cookies, network access, or permissions that the renderer does not.
3. Test whether content appears after the initial load
When JavaScript or asynchronous resources populate the page after it first loads, Html2Pdf.app’s waitFor option lets you delay PDF generation. The documented range is 0–10 seconds, with a default of 0 (documentation). Try a short delay only when the page’s content is late-arriving; it is a diagnostic, not a fix for inaccessible assets or failed scripts.
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Compare the same input with the default and with a modest delay. If the output changes, investigate which content is loaded asynchronously and whether it can be made available more reliably. Increasing the delay indefinitely is not possible within the documented range.
4. Compare screen and print CSS
The media option accepts screen or print, and defaults to screen. A page can look different under print styles—for example, a stylesheet may hide elements in one mode. Generate with the mode that matches the intended document and compare the result when the page uses media-specific CSS. The option selects the media mode; it does not repair missing stylesheets.
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5. Save a synchronous PDF without corrupting its bytes
This cURL example sends raw HTML and writes a successful response to a file. Replace the key and HTML as needed. The status check prevents an API error response from being mistaken for a PDF.
curl -sS -D response-headers.txt -o output.pdf
-X POST "https://api.html2pdf.app/v1/generate"
-H "X-API-Key: YOUR_API_KEY"
-H "Content-Type: application/json"
-d '{"html":"<html><body><h1>Hello PDF</h1></body></html>"}'
Inspect the status in response-headers.txt. Only treat output.pdf as a completed PDF when the request succeeded; on an error, examine the response body and correct the documented cause. For a URL input, use that public URL as the value of html. See the official cURL integration guide and parameter reference for the service’s current request details.
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6. Handle callback mode as a separate response flow
If the request includes callBackUrl, a successful initial response is 202 Accepted, which means the job was queued. It does not contain the finished PDF. The callback JSON contains a base64-encoded document value; decode that value to bytes before writing the PDF. Do not save the 202 response body as the document.
7. A compact diagnostic sequence
- Check the HTTP status and whether the request is synchronous or uses
callBackUrl. - For synchronous success, preserve the response as binary PDF bytes; for callback mode, wait for the callback and decode its base64
document. - Verify that the URL is public or that raw HTML’s stylesheets, fonts, and images are reachable by the renderer.
- If page content is inserted late, compare the default with a suitable
waitForvalue from 0 to 10 seconds. - If the page has print-specific CSS, compare
screenandprintmedia.
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