Imagine this scenario:
You have a burning desire to uncover a secret buried in your family's past. You worry that, despite your diligent research efforts, you may never find the records needed to confirm the truth of the matter. However, when you learn about the capabilities of genetic genealogy, you realize that taking a DNA test may lead you to the answer you've been seeking. The holidays are coming up, and sales prices at Company A give you just the push you need: you purchase their DNA test and eagerly await the discoveries you're sure will lead to your answer.
Meanwhile, on another part of the planet, someone else has a burning desire to uncover a family history secret, too, and decides to purchase a DNA test. What neither of you know at this point is that the clues embedded in this unknown person's test kit contain the very answers you are seeking. But while you decided to purchase your DNA test through Company A, this mystery cousin bought a kit from Company B.
One obvious solution to overcoming such a problem would be to purchase a DNA kit at every company offering their services for genealogical purposes. But that could become expensive.
There is a work-around to that problem: test first at a company which boasts a large database, then upload your raw data from that company to another DNA company which permits such a process. The reason for this is that such transfers can be accomplished at much smaller cost (in some cases, for free)—and often at a fraction of the wait time.
The DNA companies which offer customers only their own direct testing services are AncestryDNA and 23andMe. Those two also happen to boast the largest databases. The other DNA companies used for genealogical purposes include MyHeritage, Family Tree DNA, and Living DNA, all of which accept uploads of raw data from DNA tests conducted through the first two companies mentioned (in addition to selling their own DNA kits).
Uploads can generally be performed for free, but depending on the company, that free offer may only provide limited access to the company's tools and resources for examining test results. For instance, uploads to MyHeritage are free, but only allow access to a list of DNA matches and the ability to contact those matches. For someone not already a subscriber to MyHeritage's family history services, accessing MyHeritage's helpful DNA analysis tools, such as the chromosome browser, can be accomplished by a one-time "unlock" fee. That fee is currently $29 (U.S. dollars), but I have seen promotions in which even that fee has been waived. Still, $29 is a far more reasonable expense than springing for a second autosomal DNA test.
There are upload instructions available for each vendor. MyHeritage provides both written instructions and a video tutorial (scroll to the end of the article) for those interested in seeking matches at this next-largest DNA company. Likewise for Family Tree DNA and Living DNA, there are instructions per each vendor upload.
Over the years, I have heard so many stories of people looking for answers by testing at one company—while their answer, unsuspectingly, was waiting to be discovered at another company. That was the founding premise behind GEDmatch: to provide a place where researchers could find each other by uploading their test results to that one location. Yet, not everyone is willing to upload data to yet another website. Far better to make yourself available than to hope everyone else will accommodate you. That, at least, is the thinking behind uploading your own results directly to those DNA companies which will allow such a process.