What file formats can you fax?

Why file format matters

A fax machine prints your document on paper at the other end. To make that happen, your digital file needs to be converted into a fax-compatible image. A process that happens automatically when you use unofax.

Most common file formats work well, but understanding which ones produce the best results can help you avoid blurry pages or formatting surprises.

Supported file formats

unofax accepts a wide range of file types. Your file is converted automatically. No extra software needed.

• PDF: the most common format for faxing. Multi-page PDFs are supported and each page is sent as a separate fax page.
• Word (.doc, .docx): Microsoft Word documents are converted and formatted automatically. Fonts and layout are preserved as closely as possible.
• PNG: ideal for screenshots, scanned documents, and images with text. Supports transparency, which is flattened to white for fax.
• JPEG: good for photos and scanned pages. Use the highest quality setting when saving to avoid compression artefacts.
• GIF / WebP: common web image formats. Both are converted automatically and work well for simple graphics and screenshots.
• HEIC / HEIF: the default photo format on iPhones and iPads. Upload directly from your device. No conversion needed on your end.
• TIFF: a lossless image format widely used for scanned documents, medical imaging, and legal archives. Both .tif and .tiff extensions are supported.

Tips for the best fax quality

A few simple choices can make a noticeable difference in how your fax looks when it arrives:

• Use PDF when possible: PDF preserves layout, fonts, and resolution better than most other formats. If you have a choice, save or export your document as PDF before uploading.
• Use high resolution: aim for at least 200 DPI. Low-resolution files may appear blurry or hard to read on the receiving end.
• Keep it black and white: fax machines print in black and white. Documents with high contrast (dark text on a light background) produce the clearest results.
• Avoid photos of documents: a photo taken with your phone often has uneven lighting, skew, and low contrast. Scan the document or use the original digital file instead.
• Check the preview: unofax shows a page-by-page preview before you send. Use it to catch any formatting issues, cropping, or missing content.

What if my file is not supported?

If your file is in a format that unofax does not accept, the simplest solution is to convert it to PDF first. Most applications have a "Save as PDF" or "Print to PDF" option built in.

On a phone, you can usually share a file to your printer and choose "Save as PDF" instead of printing. On a computer, opening the file and selecting File → Print → Save as PDF works in almost every application.

Common questions

Quick answers to the questions we hear most often about file formats:

• Can I fax a password-protected PDF?: No. You need to remove the password before uploading. unofax cannot open or convert files that are encrypted or password-locked.
• Can I fax a multi-page file?: Yes. Multi-page PDFs and Word documents are fully supported. Each page is sent as a separate fax page.
• Can I fax a scanned document?: Yes. Save your scan as PDF, PNG, or JPEG and upload it. For the best quality, scan at 200 DPI or higher in black and white mode.
• Is there a file size limit?: unofax accepts files up to 10 MB. If your file is larger, try reducing the image resolution or splitting it into smaller files.