According to European patent law, an invention has to be new to be patentable, i.e., it should not have been disclosed to the public before filing a first patent application. In Europe, the novelty is absolute: any disclosure, by anyone, by any means, is prejudicial to the novelty of the invention. There are only two exceptions: evident abuse and display at some officially recognized international exhibitions.
Therefore, if you show your invention on a website, on a LinkedIn page, or on a YouTube movie, the shown information can be held against the novelty of your future European patent.
The situation is different in the US: a disclosure of the invention by the inventor, or somebody who obtained it from the inventor, not more than one year before the filing date of the patent application, cannot be held against the novelty.
Our advice: keep your invention confidential until the filing of a patent application! If it is too late, and the invention has already been published, file a US patent application within one year from the publication.