MOBI to FAX Converter

Convert MOBI ebook pages to FAX format — free online

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Fax-Ready Output

Render MOBI ebook pages as Group 3 FAX images — formatted for direct transmission through fax machines and fax server applications.

Instant Processing

Fax images are compact and simple to generate. MOBI to FAX conversion completes in seconds — pages are ready for transmission quickly.

Browser-Only Workflow

No fax software needed for the conversion step. Convertio creates FAX-format images entirely online from your MOBI file.

How to convert MOBI to FAX

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose fax or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your fax file right afterwards

About formats

MOBI is an ebook format originally developed by Mobipocket SA, a French company founded in 2000 that was later acquired by Amazon in 2005. The format builds on the PalmDOC/PDB container structure, adding support for HTML-based content markup, embedded images, a DRM layer, and a JavaScript subset for limited interactivity. MOBI files use a record-based database architecture inherited from Palm OS, with a header structure containing metadata like title, author, publisher, and language followed by compressed HTML content records. The format became the foundation of Amazon's early Kindle ecosystem — the original AZW format used on first-generation Kindles was essentially MOBI with Amazon's own DRM wrapper. MOBI supports reflowable text with basic formatting including bold, italic, headings, lists, and tables, as well as internal hyperlinks and a built-in table of contents. One advantage is broad device compatibility: MOBI files are recognized by Kindle devices and apps spanning over a decade of hardware, as well as numerous third-party readers on desktop and mobile platforms. The format's lightweight structure is another strength — even long novels produce compact files that load quickly on modest hardware. While Amazon has since moved to the more capable AZW3/KF8 format for new publishing, MOBI remains widely circulated in existing ebook libraries and continues to be produced by conversion tools like Calibre for maximum Kindle compatibility.
Developer: Mobipocket SA
Initial release: 2000
FAX is a generic image file extension associated with facsimile transmission formats standardized by the ITU-T (formerly CCITT), with the underlying Group 3 compression standard ratified in 1980. FAX files typically contain monochrome (1-bit, black and white) image data compressed using the Modified Huffman (MH) encoding defined in ITU-T Recommendation T.4, which assigns variable-length codes to run lengths of consecutive white or black pixels along each scanline. The standard resolution for Group 3 fax is 204x98 dpi (normal mode) or 204x196 dpi (fine mode), reflecting the capabilities of thermal and laser fax machines of the era. FAX files encountered digitally are often raw Group 3 encoded bitstreams or TIFF wrappers with CCITT Group 3 compression (TIFF compression tag 3). The Group 3 encoding scheme is highly efficient for typical business documents — pages with mostly white space and black text — achieving compression ratios of 10:1 to 20:1 compared to uncompressed bitmaps. One advantage is universal fax system compatibility: Group 3 encoding is the mandatory baseline for all fax machines worldwide, meaning FAX files contain data in exactly the format transmitted over telephone lines, preserving the original fax data without transcoding losses. The format's role in business communications history provides another dimension — billions of fax transmissions using this encoding moved legal documents, medical records, and business correspondence for decades, and archived FAX files represent an important documentary record. FAX images can be viewed and converted using LibreOffice, ImageMagick, GIMP, and standard document management systems.
Developer: ITU-T
Initial release: 1980

Frequently Asked Questions

Why convert MOBI to FAX?

FAX format produces images compatible with fax machines and fax software — useful when you need to transmit ebook pages via traditional fax systems.

How do I open a FAX file?

Windows Fax Viewer, IrfanView, XnView, and fax server software handle FAX image files. Many multi-function printers also process this format.

Is the FAX format monochrome?

Group 3 FAX is typically monochrome (black and white), optimized for text documents — which works well for text-heavy ebook pages.

Can I send the output directly to a fax machine?

The FAX images are formatted for fax transmission. Use them with your fax software or online fax service to send ebook pages via fax.

Will text be readable after conversion?

Yes — fax resolution is designed for readable text documents. MOBI pages with standard text render clearly in the FAX output format.