Historically, TV commercials were pretty well limited to either 30-second or 60-second spots, but the advent of online video changed all that.

Now, the best video ads can run anywhere from 6 seconds (think Vines) to three or four minutes or more.

It's all about storytelling, and brands are getting better and better at it.

Coming up with the most popular commercials for online audiences is no easy feat, but it's critical. People don't share what they don't like, and videos don't go viral without shares.

I recently spent more time than I should probably admit to enjoying a collection of top video ads curated by readers over on the Moz blog. Wizard of Moz (that's a real thing, you guys) Rand Fishkin asked his readers to share the most epic, mind-blowing ads they'd seen, and they delivered in spades.

I'll share a few of my personal favorites here. Check these out:

Ideas Are Scary - GE

"Ideas are the natural born enemy of the way things are."

Doesn't THAT resonate! In this one-minute short, GE literally brings an idea to life. In a way, they humanize this concept of idea creation and building.

Anyone who's had their own ideas shot down by investors should totally get this commercial.

Rule Yourself - Under Armour

This epic 1m30s clip is one of the best video ads I've seen all year. It sets to music the incredible journey of swimming champion Michael Phelps, and could there have been a more timely video in light of his retirement?

Like a Girl - Always

The message in Always' #likeagirl nearly three-and-a-half minute video clip clearly resonated with a ton of people.

The best advertisements elicit an emotional response from viewers, and Always succeeds. This empowering video examines what it means to do things "like a girl" and has been viewed over 62 million times on YouTube!

The Scarecrow - Chipotle

What a crazy time we live in.

Did you ever think you'd live to see the day food brands published short films to promote their app-based game?

It's a brave new world, and Chipotle is killing it with this futuristic depiction of the quest for wholesome foods. The best advertisements grab your attention and keep you with the story from start to finish, a mission the Mexican food brand easily accomplished with this creative short.

The Hero: A Bollywood Story - Google India

At almost six minutes, this is definitely one of the longer video commercials I've ever seen.

But the story is interesting, the music is engaging, and the overall message really tugs on the heartstrings. Google brilliantly tapped into the power of Bollywood's cinematic style while showcasing their search product as a natural part of their characters' journey.

Amazing storytelling.

World's Toughest Job - American Greetings

The reactions on interviewees faces as the "interviewer" explains that the job requires 24/7 work are hilarious. Every holiday, your workload goes up. You should have a degree in medicine AND finance. 

You can see the interviewees thinking, is this guy for real?

The brand really gets you invested in seeing how the whole thing turns out and the result is a totally share-worthy video.

Have you seen other great examples of brand storytelling via online video? Share your favorites in the comments below. Check out the comments on this blog post at Moz for dozens more amazingly inspiring and popular commercials.