A computer needs a browser and nothing else

Windows still ships Windows Fax and Scan. It is a real program, it is in the Start menu, and it has been there since Vista. What it needs in order to send anything is a fax modem — an expansion card or a USB device with an RJ-11 telephone jack on it — and an analog phone line plugged into that jack. No modem, no line, no fax. The program does not say so until you try.

macOS used to have the same capability, as a Fax option in the print dialog. Apple removed it along with the modems; on a current Mac the option is not there at all. This is the whole of the confusion: the operating systems kept the vocabulary of a feature whose hardware stopped shipping around 2009.

Sending over the internet skips the hardware question entirely. The analog call still happens — it has to, because the machine at the other end is analog — but it is placed by a carrier’s equipment rather than by yours.

Where you can fax something is the guide for readers who would rather take the pages to a counter: it covers which kinds of counter are worth a phone call first, and when the trip buys you nothing. Everything below assumes the browser.

If the thing you need to fax is open in an application rather than sitting in a folder — a spreadsheet, a filled-in form, an email, a web page — print it to a file first. Ctrl-P on Windows and choose Microsoft Print to PDF; Cmd-P on a Mac and choose Save as PDF from the PDF menu at the bottom left. That file is what you upload.

It is also the right thing to do rather than a workaround. Printing is the step where the application decides page breaks, margins and what fits on a sheet. Doing it first means you can see the pagination before it becomes a fax, instead of discovering that a table split across two pages in a way the recipient will find hard to read.

Every page is converted to the format the fax network actually carries: 1728 pixels across, letter-sized at roughly 204 × 196 dpi, each pixel black or white. Those two resolutions are different, so a fax pixel is not square — fitting your page is done in real page units and converted to the pixel grid afterwards, because comparing pixel counts instead stretches a scanned form vertically by about four percent, which is enough to see.

Anything that does not fit the letter aspect is centered on white rather than cropped or stretched. A fax that silently loses the right-hand inch of a form is worse than one with a visible margin. You see all of this in the preview before paying; faxing a PDF goes through what survives the conversion and what does not.

Needed

A browser

Not needed

Modem, phone line, driver, software, account

Accepted files

PDF, JPG, PNG, HEIC

Pages in one fax

Up to 30, cover page included

Destinations

Any US fax number

A cover letter, a signed form and two exhibits are four files and one fax, at one price, transmitted in the order you put them in. This is the case the 30-page limit exists for — the alternative, when a service caps a send at a handful of pages, is finding a PDF splitter and paying several times for one submission.

• How do I send a fax from my iPhone?
• How do I send a fax from an Android phone?
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• How do I fax a PDF?
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• Do I need a fax cover sheet, and what goes on it?
• How do I send a test fax to check that a line works?
• What number can I send a test fax to?
• What has to be on a HIPAA release form, and where does it go?
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• Where can I fax something?