Firefox PDF Looks Blank in the Browser but Opens After Download?
Use the PDF viewer’s download control and compare the local file before changing every PDF action.
With the blank PDF open in Firefox, use the viewer’s Download button. Open that saved copy in another PDF reader. Mozilla notes that some PDFs can display with missing fonts, colors, or pages in the built-in viewer. If only Firefox is blank, review extensions and PDF file actions.
Separate the file from the viewer
A blank Firefox tab does not prove the PDF itself is empty. Download the document using the viewer’s control and open the same saved file in another reader. Check more than the first page, because a font or color problem can make only part of a document seem missing.
- Confirm the downloaded file has a nonzero size.
- Open the identical file in a different PDF reader.
- Try a second known-good PDF in Firefox.
Check Firefox’s PDF handling
Mozilla documents a built-in PDF viewer as well as actions that save a file or open it in another app. If a particular document does not render well, using the saved copy with the default PDF app is the supported workaround. Change the PDF action in Firefox Settings only if you want future PDFs to behave differently.
If all PDFs fail in Firefox, test with extensions disabled. Mozilla notes that an extension can interfere with the built-in viewer. Restore extensions one at a time to identify the one affecting PDFs.
When the saved copy is blank too
The source document or download itself may be faulty. Re-download it from the publisher’s page and check whether their preview also looks blank. If the document is important, ask the publisher for a replacement or an accessible version rather than repeatedly printing an empty page.
If you edited a PDF in Firefox, make sure the saved version includes your changes before closing the original tab.