PDFShift’s documented conversion endpoint accepts either raw HTML or a page URL, but its published guides do not define the exact 422 invalid HTML message or identify one certain cause. Start by saving the complete response body, then check the request format and investigate the selected source path—raw HTML or URL—separately.
1. Capture the full error before changing the request
Record the HTTP status and complete response body for the failed call. PDFShift’s examples show checking unsuccessful responses and exposing the returned content; its aiohttp guidance also recommends handling error details and notes that an error response does not contain a PDF. Do not log your API key or sensitive document contents.
The response body is the best available clue to what this particular request failed on. The available PDFShift guides do not establish that every response labeled 422 invalid HTML means the markup itself is malformed, so avoid treating the status text alone as a diagnosis.
2. Verify the documented request shape
PDFShift documents a POST request to https://api.pdfshift.io/v3/convert/pdf. The JSON body should include source, whose value is either HTML content or a URL. Confirm that your client is actually sending a JSON body to that endpoint and that the API-key configuration is correct for the client or workflow.
The Tool Desk
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These checks validate the documented envelope; they do not prove that a mismatch caused this exact 422. Compare the request your code constructs with the request that reaches the API, taking care not to expose credentials in logs.
3. Diagnose raw HTML and URL sources separately
If source contains raw HTML
- Confirm the entire generated HTML document is passed as a JSON string, not as an unencoded fragment or a differently named field.
- Use your JSON library to encode quotation marks, backslashes, and newlines. Avoid manually assembling JSON, where escaping errors can change the submitted value.
- Try a small valid HTML document, then add your template output, styles, scripts, fonts, and images back in stages. This is a diagnostic isolation technique, not a documented PDFShift fix for the exact 422.
If source contains a URL
- Check that the URL is reachable by PDFShift’s conversion service, not merely by your own browser or server.
- Look for login requirements, inaccessible routes, redirects, or other access controls that could prevent retrieval.
- PDFShift documents a
raise_for_statusoption for making a failed remote-source load fail the conversion. Use it when appropriate so a retrieval failure is surfaced rather than mistaken for a rendering problem. - If the URL fails, try the corresponding HTML as a raw source where feasible. That helps distinguish remote retrieval from content handling.
Raw HTML and URL inputs are distinct paths: inspect JSON encoding and generated markup for the former; inspect reachability, access controls, redirects, and dependent resources from the service’s perspective for the latter.
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4. Reduce external dependencies to isolate loading problems
PDFShift recommends reducing network requests during conversion. Its Help Center says, “Generally speaking, avoid any network requests.” It recommends sending raw HTML instead of having the service fetch a URL, inlining CSS and JavaScript where possible, removing unnecessary scripts, considering base64 image data, and optimizing image sizes. These steps can make conversion faster and simplify diagnosis, but they are not documented as guaranteed remedies for 422 invalid HTML.
A controlled test sequence
- Submit a minimal valid HTML document as raw HTML.
- Add your generated template content and verify the response after each change.
- Reintroduce stylesheets, scripts, fonts, and images in small groups.
- If using a URL, compare it with raw HTML and investigate remote access separately.
- Keep the full response body for each attempt so you can associate any changed error with the specific input change.
5. Common symptoms and next steps
| Observation | What to check | Next step |
|---|---|---|
The response says 422 invalid HTML, with no clear detail |
The exact response body and the submitted request envelope | Check endpoint, POST method, JSON body, source, and API-key configuration; then test the relevant source path. |
| Raw HTML fails | Whether the complete document is correctly encoded as a JSON string | Use a JSON encoder and test a minimal document before adding template output and assets. |
| A URL source fails | Whether PDFShift can retrieve it without a login or blocked route | Check redirects and access controls; use raise_for_status where appropriate to expose remote-load failures. |
| A simpler document works, but the full page does not | External resources and recently added markup or scripts | Add components back in stages; consider inlining or removing unnecessary network-dependent assets. |
| The message remains ambiguous | Whether the response body identifies a specific validation condition | Send PDFShift support the full response body and a minimal reproducible request, with secrets and sensitive content removed. |
The documented pages do not specify whether this exact message indicates malformed markup, a missing or mis-encoded source, or another validation condition. Attribute a cause only when the response payload or PDFShift support confirms it.
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