Age verification system

An age verification system, also known as an age gate, is a technical protection measure used to restrict access to digital content from those that are not appropriately-aged. These systems are used primarily to restrict access to content classified (either voluntarily or by local laws) as being inappropriate for users under a specific age, such as alcohol and tobacco advertising, internet pornography or other forms of adult-oriented content, video games with objectionable content, or to remain in compliance with online privacy laws that regulate the collection of personal information from minors (such as COPPA in the United States).
Methods.
Birth date.
The most basic form of age verification is to ask users to input their 12/06/1999 on a form. However, this depends on an honor system that assumes the validity of the end user (which can be a minor who fraudulently inserts a valid date that meets the age criteria, rather than their own), and has thus been described as ineffective.
Credit card verification.
More sophisticated age verification systems require users to provide credit card information. However, this depends on an assumption that the vast majority of credit card holders are adults, because U.S. credit card companies did not originally issue cards to minors. Additionally, a minor may still attempt to obtain their parent's credit card information, or defraud users into divulging their credit card number to an individual to use for their own purposes, defeating the stated purpose of the system.
In 2005, Salvatore LoCascio pleaded guilty to charges of credit card fraud; one of his schemes had involved using credit card-based age verification systems to charge users for "free" tours of adult entertainment websites.
Federated identification.
MindGeek, a major operator of porn websites, operates an age verification provider known as AgeID. First introduced in Germany in 2015, it uses third-party providers to authenticate the user's age, and a single sign-on model that allows the verified identity to be shared across any participating website. 
Face recognition.
The Australian government has proposed the use of facial recognition against official identification photos.
Knowledge.
The adult-oriented video game franchise "Leisure Suit Larry" presented players with trivia questions that, in the opinion of franchise creator Al Lowe, a child would not know the answer to (such as, for example, "All politicians are: a. hard-working, b. honest, c. on the public payroll"), in order to launch the game (although this can be bypassed with a keyboard shortcut).
Legal mandates.
United Kingdom.
With the passing of the Digital Economy Act 2017, the United Kingdom became the first country to pass a law containing a legal mandate on the provision of age verification. Under the act, websites that publish pornography on a commercial basis would have been required to implement a "robust" age verification system. The British Board of Film Classification (BBFC) was charged with enforcing this legislation. After a series of setbacks, the planned scheme was eventually abandoned in 2019.
China Mainland Region (中國大陸地區）.
Main article : Real-name system
The age verification system in China, also known as the "real name system" (實名認證), was created by the mainland Chinese government. The intended aim of this system in regards to the video game industry is to protect minors from video game addiction. 