The `<input pattern>` attribute allows developers to specify a regular expression pattern against which the input’s values are checked for validity. ``` <label> Part number: <input pattern="[0-9][A-Z]{3}" name="part" title="A part number is a digit followed by three uppercase letters."> </label> ``` When the `pattern` attribute was first implemented, these regular expressions were compiled without any RegExp flags. In 2014, the HTML Standard changed this by implicitly enabling the `u` flag for the pattern attribute, enabling better Unicode support (including support for Unicode character properties like `\p{Letter}`). This change shipped in Chrome 53 (https://chromestatus.com/feature/4753420745441280). Now, we’re taking this to the next level by enabling the new RegExp `v` flag instead of `u`, enabling the use of set notation, string literal syntax, and Unicode properties of strings. (Context: The RegExp `v` flag is a JavaScript language feature which previously went through the Blink Intents process, and is now shipping in Chrome 112: https://chromestatus.com/feature/5144156542861312 This new ChromeStatus entry is specifically about integrating it with the HTML `pattern` attribute.)