8chan is the public website where Q posts intel drops. It is the one and only place where Q will post anything online. There are other websites, such as qmap.pub or qanon.pub, that scrape Q's drops and aggregate them for easier navigation and consumption. But Q will only post on 8chan. Anyone claiming contact with Q via any other means is lying to you.
Many people wonder why Q would pick 8chan of all places. After all, 8chan is not a mainstream website like twitter, reddit or facebook. There are many good reasons why Q would pick 8chan, here are a few:
1) 8chan is not under control of Big Tech and is therefore free of censorship. If Q was on twitter or facebook they would be banned immediately.
2) Q and POTUS needed a direct and public communication channel to circumvent the corrupt and anti-American mainstream media who would never cover the topics that Q brings up.
3) 8chan is associated with autists who are very smart, are truth seekers who question everything, and are incredibly skillful online researchers and meme makers.
4) Memes are clever and witty graphics/videos that point out hypocrisy and make you laugh. They are highly effective communication tools in the modern era of short attention spans and can also bypass Big Tech filters. Q has asked the autists 8chan to engage in meme information warfare to combat the false narrative of the mainstream media.