The European Travel Information and Authorization System (ETIAS) will be implemented in 2024.

ETIAS System to Begin in 2024
The European Travel Information and Authorization System (ETIAS) will be implemented in 2024. It is a security measure for travelers to certain European countries in the Schengen Zone. Countries requiring the authorization are: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden and Switzerland.
US nationals traveling to these countries will need to apply through the ETIAS website, providing basic and background information, and pay a fee of $7.79. Most will receive approval within minutes. Some may take up to four days and up to 14 days if additional documentation is requested. In some cases, results could take up to 30 days if an interview is required.
Once approved, the travel authorization is valid for up to three years, allowing stays of 90 days within a 180-day period. However, entry is not guaranteed, as border officials will review the information and can still refuse entry. It is advised to apply well in advance due to potential processing delays.