Here is CodePen's justification for requiring a referrer: https://blog.codepen.io/2017/10/05/regarding-referer-headers/ https://blog.codepen.io/2017/10/05/rega

Here is CodePen's justification for requiring a referrer: https://blog.codepen.io/2017/10/05/regarding-referer-headers/ https://blog.codepen.io/2017/10/05/regarding-referer-headers... They don't say why exactly though.