If you start a new project it might be ok and clean to add * { box sizing: border-box; } at the beginning so you can use it on the entire project and everyone else developing on the project will see it.

BUT if you work on an existing project and then just add * { box sizing: border-box; } somewhere could mess up the entire layout! So there it might be "safer" to only add it to the containers you are working on with something like .border-boxed-container * { box sizing: border-box; } . Or have an extra class like "border-boxed" which you can add to every element accordingly the CSS .border-boxed { box sizing: border-box; }

这不是一件对或错的事情。根据具体情况，使用border-box或content-box都有很好的理由。当创建需要在大小方面相对于同一行中其他内容精确时（例如需要每行总计100%的网格系统），使用border-box将简化事情并减少意外。但是如果您需要精确地调整元素相对于其内部的大小（例如，与固定大小图像完美匹配），content-box更有意义。