To confirm you are a human and not a bot, many websites now use a simple yet effective method.
When prompted to complete this step, users press and hold a key on their keyboard, usually the one between ‘a’ and ‘s’. The duration of holding the key is crucial, as it varies from 1-3 seconds.
Some websites display an animation or a countdown timer that ends once the user releases the key. Others might show a pop-up or a message asking users to confirm they are human.
This simple verification method helps prevent automated scripts and bots from accessing sensitive information or performing actions on websites, protecting both users and website administrators.
Source: https://www.sfgate.com/travel/article/tsa-bans-new-item-travelers-checked-luggage-20892654.php