h Removal (h抜き, Etchi Nuki) refers to the etiquette of removing the “h” in “http://” or “https://” as most websites automatically convert URLs into direct links and there are reasons why direct links might be discouraged in some parts of the internet.

The theory behind dropping the “h” is that search engines won't crawl the target website if there's no direct link to it and website owners are denied the ability to see what webpage you came from. On top of that, it's also a workaround for communities that deny posting links to ward off spam bots.¹⁾ In a way, it's kinda like how people don't blatantly post their email address in order to avoid being put on spam mailing lists.

However, the negative is that it can be inconvenient for some users, but most modern web browsers will be able to recognize links with the first “h” removed as a typo and bring you to the right page. It's also sorta meaningless if developers allows links with the first “h” removed to be recognized as links anyways, meaning you'll have to use other methods like changing the “t”s in “http://” or “https://” to “x”s.

• It's believe that this started on 2channel, but the reason is unknown. Some say that users didn't want unauthorized porn websites with copyrighted content to get sued by copyright holders, while others say they were annoyed by the “jump.2ch.net” page or didn't want the website to gain ad revenue.

• h Removal on Niconico Encyclopedia
• h Removal on Japanese Wikipedia