How to See Full Telegram Channel History Without Login (the ?before= Trick)

Public Telegram channels offer a web preview at t.me/s/channelname, displaying the last twenty posts as HTML without requiring a login or API key. Each post includes a monotonically increasing post ID. To access full history, users can utilize the before parameter by visiting t.me/s/channel?before=postid, which renders the page ending at that specific post ID. This method corrects outdated claims that Telegram channel history is private and inaccessible without an account or specialized tools.