Some sport-event organisers make use of personally allocated (or loan) timing chips; others make use of once-off-use timing strips; and others make use of allocated barcodes; whereas others continue historical practices of race numbers with a tear-off portion.
I learned the hard way how important it is to complete all required information on the race number tear-off, before handing it in after crossing the finish line. To this day I have not received results for my first township run. I collected my race number early morning, before the race. Having registered online; having experienced the use of both barcodes and timing strips; congestion within the collection roof; limited time before the race started; and not seeing any pens available; I assumed I need not bother.
I pinned my number to my chest, joined the see of people awaiting the start, and the race was set off shortly after. A shuffled the first distance and started running as soon as space permitted. Found a good rhythm while observing the township awakenings as a bunch of people ran through it. I finished my run in (for me) a very good time, received a medal, but to this day no result.
There are companies that specialises in printing stickers for athletes to just stick on, instead of filling out.
Events that make use of sophisticated technology even sms (short message—or messaging—service) a text message to the mobile phone of athletes as they go through the finish line. Some events make use of electronic mats that pick up the timing devices of athletes as they pass over the start mat, some even scan along the way to monitor progress, and again as athletes pass the finish line.
It is further important to carefully check what is captured when doing an online entry. When failing, for example, to change the default gender/sex, one may receive a T-shirt designed for the opposite gender, or receive a goody bag containing stuff for the opposite gender.