The short answer
You can send one file per fax, up to 100 MB. PDF is the safest choice, but office documents (Word, Excel, PowerPoint, RTF, OpenDocument), plain text (.txt, .csv) and images (JPG, PNG, TIFF, GIF, WebP, AVIF) are accepted too.
Anything that is not already a PDF is converted to PDF first, then faxed. You can do all of it from a computer or from a phone: see faxing from your phone.
The accepted formats
Documents: PDF, Word, Excel, PowerPoint, OpenDocument and RTF. Pictures: JPG, PNG, WebP, GIF, TIFF and AVIF. Plain text: .txt and .csv. Each fax takes one file, with a ceiling of 100 MB.
If you have several documents, merge them into one PDF before uploading. Most computers and phones can do that in a couple of taps.
What conversion does
A fax machine only understands black-and-white pages, so every file ends up as a PDF and then as a fax page. Word, Excel and slide files are turned into pages with the layout they have on screen, which is why a spreadsheet wider than a page can split across sheets.
For anything where layout matters, export the file to PDF yourself and check it first. What you see in the PDF is what will be faxed.
Photos and scans
A phone photo of a paper form works, provided the page is flat, well lit and fills the frame. Dark corners and shadows turn into grey blocks on a fax. If the photo is of a signed page, check that the signature is still readable at normal size.
More tips on legibility are in the answer about fax quality.
Pages and price
The format has no effect on price; only the number of pages does. A one-page document is free and anything longer costs a flat €3.99, as described on the rates page.
Worth remembering
- One file per fax, 100 MB at most.
- PDF, images, text, Word, Excel, PowerPoint, OpenDocument and RTF are accepted.
- Non-PDF files are converted to PDF before sending.