Should you justify or left-align text?

I’m just noting this in case I forget. You should left-align text most of the time.

For those who don’t know, justifying text means inserting spaces between words to fill the whole column.

For example, this is some left-aligned text:

Well, the way they make shows is, they make one show. That show's called a pilot. Then they show that show to the people who make shows, and on the strength of that one show they decide if they're going to make more shows. Some pilots get picked and become television programs. Some don't, become nothing. She starred in one of the ones that became nothing.

</p>

And this is some justified text:

Well, the way they make shows is, they make one show. That show's called a pilot. Then they show that show to the people who make shows, and on the strength of that one show they decide if they're going to make more shows. Some pilots get picked and become television programs. Some don't, become nothing. She starred in one of the ones that became nothing.

</p>

On the web you should left-align text instead of justifying it, for two reasons:

• first, if you turn on justifying, you’ll need to have hyphenation enabled too. Otherwise the browser will insert big “bubbles” between your words. The problem is automatic hyphenation is still and draft and only available on a third of all browsers.
• second, most books use justifying, but magazines do use both, so your text won’t look unprofessional.

Reference: Butterick’s practical typography