You need to master both Flexbox and CSS Grid in order to professionally build modern websites & web apps. If you haven't mastered both of them yet, I highly recommend going through my CSS Course.

Usually, to center flex items vertically we can use align-items:

(I'm also using justify-content here to center the flex-items horizontally)

But what if we have more flex-items or flex-items that are much bigger so that they wrap onto a new line?

If you still use align-items then it will look weird. Now we actually need to use align-content.

By the way, if you change the flex-direction to column, the align-items and align-content properties will now center horizontally instead of vertically. And the justify-content property will now center vertically (so they 'flip').

Conclusion: use align-items if you have just 1 row or 1 column of flex-items. Use align-content if you have multiple rows or columns after flex-items wrap onto new lines.

By the way, I think CSS is the 'bottleneck' to most websites & web apps. I believe it's the highest-ROI skill you can master.

Before I mastered CSS, I lost a ton of time & energy fiddling around with CSS.

I was learning about advanced JavaScript topics when I couldn't even implement basic layouts in CSS...

So I created a CSS course to help you avoid the same mistake. Check it out here if you're interested.

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