If you have an Apple keyboard, with a U.S. keyboard layout, things are simple. To type a hashtag sign, hit Shift + 3 . You’ll notice that the euro sign has also disappeared.

If you have a US Mac keyboard then you will see that the hashtag is a secondary option on the 3 key. All you need to do is hold down the Shift key and press 3 . If you did this on a UK Mac ...

In an app on your Mac, press and hold a key on the keyboard-for example, a-to display the accent menu. The menu isn't shown if a key doesn't have any possible accent marks. Select a character in ...