Results come from the official timing platform each series uses — SiTiming, RaceTec, my.raceresult, RacesOnline / Webscorer and others — imported with organiser approval, or uploaded directly by clubs. Every race page credits its source.
The source link on each race page goes back to the timing platform's original record, so you can always check a result against the provider's copy. Nothing is entered by hand: if a race isn't here it's because no official source has been published or approved for import yet.
Club uploads go through the same pipeline — see the uploading results article for the organiser flow.