Thank you. But that's not exactly what I mean. As I wrote in the first question, I need a unique key that will automatically identify the user. If there is a need to "manually" set it on the website, I can also set it in the bot by asking the user, for example, to log in. I want to be able to check in the bot whether the user has already used the bot or whether this is his first visit. If he used it, I could greet him differently and I wouldn't have to ask about his data again. If he hasn't used it, I can ask him for data. Hence the simple question is whether the event.userID variable has a value for a specific user which enable me distinguish him from other users. I tried to check if {{event.userID}} has a value using it in Text Card, but the system hangs. Is there any possible solution to this problem?