There are several types of fax freeware available for multiple operating systems. Most freeware is designed simply to send an image file to a fax machine and negotiate the communications protocols through a modem and standard phone line or a Voice over Internet Protocol (VoIP) connection. Some freeware is designed just to receive faxes in the same way or can handle both sending and receiving. More full-featured fax freeware can convert documents into image files that can be sent to a fax, or it can use open source optical character recognition (OCR) programs to convert incoming faxes into editable text files. A slightly different type of fax freeware acts as a management tool only, relying instead on free online services to perform the actual faxing, although these freeware programs may have advertising on the cover page of the fax.
One of the most commonly available types of fax freeware is a program that sends a fax to another machine in some way. These can be very basic, with only the ability to dial, connect and send an image file, or they can be more feature-rich, using modules to convert text documents into images before being sent. In general, a modem and standard phone line are required for a fax program to work, although some freeware makes it possible to use a VoIP connection to send the fax.
Less common are fax freeware programs designed to receive faxes through a modem. This is partly because it can be difficult or impractical to poll a modem for a fax signal without interrupting other devices, such as answering machines, that also poll the line. Many versions of receiving software rely on the user to indicate when a fax is incoming, making it necessary for the user to remain in front of the computer until the call comes in.
There are a handful of full-featured fax freeware suites available that make sending and receiving faxes easier. These programs can sometimes manage documents, convert them between formats and perform automatic faxing to multiple numbers in an address book. Other useful functions that can be implemented include sending converted fax documents via email, email or instant messaging notification of received faxes, and basic image editing to allow the addition of signatures or seals to faxed documents.
One final type of fax freeware is a program that does not include any type of innate functionality to send or receive faxes itself. Instead, these programs focus on creating documents and then connect to an online server through the Internet to send the fax. This has the benefit of not requiring a computer or device running the fax freeware to have a modem installed, but it has the complication of relying on a third-party service for faxing. In these instances, the freeware can be rendered useless if the main online server stops working, while also potentially removing control over certain quality-related aspects of the fax transmission.