URGENT - Google Drive "Upload a File" — "SourceUrl is not accessible (HTTP 403). Ensure the file is public."

Status: Closed · Asked by Abadesa Export Centrer SL B86507936 on · 0 views

Abadesa Export Centrer SL B86507936 — Question ·
Subject: Google Drive "Upload a File" returns "sourceUrl is not accessible (HTTP 403)" for a valid PDF.co pre-signed S3 URL

Hi Pabbly team,

I'm hitting a blocker in one of my workflows and I believe it's a handling issue on the Pabbly side rather than a permissions issue with my file.

Account: [tu email de Pabbly]
Workflow: [pega aquí la URL completa del workflow]
Failing step: Step 28 – Google Drive: Upload a File
Source step: Step 27 – PDF.co: Merge PDFs
Approx. time of the failed test: 2026-08-28, 07:37 UTC

What happens

Step 27 (PDF.co) returns a temporary download URL on pdf-temp-files.s3.us-west-2.amazonaws.com. I map that URL into the "URL (Required)" field of Step 28. The response is:

RequestStatus: Failed
Error: sourceUrl is not accessible (HTTP 403). Ensure the file is public.

Why I don't think the file is the problem

The URL is an AWS SigV4 pre-signed link. It carries X-Amz-Algorithm, X-Amz-Credential, X-Amz-Date, X-Amz-Expires=3600 and X-Amz-Signature in the query string. Anyone with the link can download it without authentication, and it was only a few minutes old when the step ran (well inside the 1-hour window).

I verified the exact same URL from outside Pabbly and it downloads fine:

curl -sSI "<pre-signed URL>"  ->  HTTP/1.1 200 OK, Content-Type: application/pdf

So the object is reachable. With pre-signed S3 URLs, a 403 is what S3 returns when the request doesn't match the signature — i.e. when the query string has been altered in any way.

What I suspect

Something in the Upload a File action appears to modify the URL before requesting it. Any of these would break the signature and produce exactly this 403:

- The query string is truncated (e.g. cut at the first & or at a character limit).
- The URL is re-encoded / double-encoded (%2F becoming %252F, & becoming &amp;).
- Trailing whitespace or a newline is appended from the mapped value.

Questions

1. Does "Google Drive: Upload a File" fully support source URLs that contain a long signed query string?
2. Is there a length limit on the URL field, and is the value truncated or re-encoded before the download request?
3. Can you check your logs for this execution and tell me the exact URL your server requested? Comparing it with the value I mapped should settle this immediately.

I'd rather not attach the pre-signed URL here since it expires after one hour and would be useless by the time you read this. Happy to re-run the workflow and share a fresh URL, or to jump on a screen share, whenever it's convenient for you.

Thanks a lot,
[Tu nombre]
Pabbly Support — Reply ·

Hello there,

Thanks for contacting us.

1. Does "Google Drive: Upload a File" fully support source URLs that contain a long signed query string?
- The file upload URL needs to be a direct download link without any query string.

2. Is there a length limit on the URL field, and is the value truncated or re-encoded before the download request?
- Pabbly encodes the link as per the Pabbly internal infrastructure to execute the upload request.

3. Can you check your logs for this execution and tell me the exact URL your server requested? Comparing it with the value I mapped should settle this immediately.
- The download URL must include the file extension at the end of the URL, like .pdf. As I can check, you have taken the correct approach by using the File upload (Pabbly) module to first upload it on Pabbly's server and generate a simple direct download URL. Now the 29th and 30th Action steps are executing normally.

Thanks & Regards,

Adeel Akhtar
🌐 Pabbly.com

John Smith — Reply ·

I am having an issue related to this as well

Pabbly Support — Reply ·

Hello John,

Could you please let us know what issue you are facing? You can create a new Forum thread as well, where you can personally share your Workflow URL for analysis. Or you can email us at support@pabbly.com directly.

Or you can continue on this thread as well.

Thanks & Regards,

Adeel Akhtar
🌐 Pabbly.com

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