C validating user input
Developers are often provided with a large amount of security advice, and it is not always clear what to do, how to do it, and how important it is.Especially considering that security advice has changed over time, it can be confusing.Most current web browsers support these features and handle input validation.Also, HTML5 validation helps users inputting data by providing specific controls, such as date pickers and custom on-screen keyboards.Depending on your web browser, the “Range” input field will be displayed as a slider control to help users provide input more easily.Similarly, the “Number” input field may be displayed with buttons to increase or decrease the number incrementally.
HTML5 defines a range of built-in functionality to validate common types of input, such as email addresses and dates.
For example, telephone numbers are written with different separators and digit groupings.
Your form will be easier to use if it can interpret multiple notations. For example, postal codes aren't confined to just numbers in some countries, so using an can easily become a problem for many of your website users.
This is useful for specific types of data patterns such as telephone numbers, postal codes, and serial numbers.
In the example below, the element specifies a particular format that matches car license plate (registration) numbers in Germany.