Amateur radio operators exchange QSL cards to confirm two-way radio contact between stations. Each card contains details about one or more contacts, the station and its operator. At a minimum, this includes the call sign of both stations participating in the contact, the time and date when it occurred (usually specified in UTC), the radio frequency or Band used, the mode of transmission used, and a signal report. One national association of amateur radio operators, the IARU Region 2, recommends a size of 3½ by 5½ inches (89 mm by 140 mm).
QSL cards are a ham radio operator's calling card and are frequently an expression of individual creativity — from a photo of the operator at his station to original artwork, images of the operator's home town or surrounding countryside, etc. They are frequently created with a good dose of individual pride. Consequently, the collecting of QSL cards of especially interesting designs has become an add-on hobby to the simple gathering of printed documentation of a ham's communications over the course of his or her radio career.
Normally sent using ordinary, international postal systems, QSL cards can be sent either direct to an individual’s address, or via a country's centralized amateur radio association QSL bureau, which collects and distributes cards for that country. This saves postage fees for the sender by sending several cards destined for a single country in one envelope, or large numbers of cards using parcel services. The price for lower postage, however, is a delay in reaching its destination because of the extra handling time involved. In addition to such incoming bureaus, there are also outgoing bureaus in some countries. These bureaus offer a further postage savings by accepting cards destined for many different countries and repackaging them together into bundles that are sent to specific incoming bureaus in other countries.
For rare countries, that is ones where there are very few amateur radio operators, places with no reliable (or even existing) postal systems, including expeditions to remote areas, a volunteer QSL manager may handle the mailing of cards. For expeditions this may amount to thousands of cards, and payment for at least postage is appreciated, and is required for a direct reply (as opposed to a return via a bureau).
Recently, the Internet has enabled electronic transmission as an alternative to the need for mailing a physical card. These systems use computer databases to store all the same information normally verified by QSL cards in an electronic format. Some sponsors of amateur radio operating awards, which normally accept QSL cards for proof of contacts, may also recognize a specific electronic QSL system in verifying award applications.
One such system, eQSL enables electronic exchange of QSLs as jpeg or gif images which can then be printed as cards on the recipient's local inkjet or laser printer, or displayed on the computer monitor. Many logging programs now have direct electronic interfaces to transmit QSO details in real-time into the eQSL.cc database. CQ magazine began accepting electronic QSLs from eQSL.cc for its four award programs in January 2009. 10-10 has been accepting eQSLs since 2002. Another, the ARRL’s Logbook of The World (LoTW), allows confirmations to be submitted electronically for that organization’s DX Century Club and Worked All States awards.
Even in the presence of electronic QSLs, physical QSL cards are often fine historical or sentimental keepsakes of a memorable location heard or worked, or a pleasant contact with a new radio friend, and serious hams may have thousands of them. Some cards are plain, while others are multicolored and may be oversized or double paged.