For my kids, email is an antiquated technology — I might as well tell them to expect a telegram. Most of the business world isn’t so lucky, however, and a fair portion of the day is spent bailing out an inbox that never stops filling up.

The worst part of email is that a lot of the information it delivers is better delivered some other way. When the subject is urgent, it takes too long. When the information is trivial, it takes too much time. And then there’s the co-worker who sends you an email from across the room … then comes to your desk to tell you to read it.

Enter Slack, described as the “email killer” when it launched in 2014. The workplace chat app was created by Stewart Butterfield, known for founding the photo sharing service Flickr. Slack spread like wildfire in the startup space, picking up over 100,000 users in its first six months. Today it has 10 million daily active users, and its customers include most of the largest companies in the Fortune 100.

While it is a chat app, it’s more flexible and powerful than most chat tools. One of its main benefits is that it works across devices and platforms, including Android, iOS, Windows, MacOS and the web.

How it works is a little harder to explain. Old-school geeks like me would say it’s a lot like IRC — Internet Relay Chat — but that probably won’t convince your boss to give it a try.

The main difference between Slack and other messaging platforms is that conversations happen in channels, labeled with the pound sign (or hashtag, to millennials and younger). While everyone in a company or group can converse in #general, the programmers can have their own space in #dev, and conversations about the next ad campaign can happen in #marketing. Jokes and cat memes can be contained in #random.

And it wouldn’t be instant messaging without emojis. Slack supports the basics and allows teams to create their own custom symbols. My favorites include the spam musubi, rainbow shave ice and shaka hand sign.

Organizing chats by topic makes a big difference, as does having conversations take place in the open. At a glance the marketing team can see that the development team is heads-down on a major release, and the designers can ask for feedback from the rest of the company. If you’ve been away from your desk, you can catch up on the morning’s developments — or office hijinks — easily.

You can set up private channels, too, say for #management or #partyplanning. And instead of sending an email to a co-worker, you can send a direct message, and the two of you can work through the details of a major project in real time.

If your team takes to Slack, you’ll find conversations flowing across a handful of channels, and your email client will suddenly feel neglected.

Best of all, everything I’ve written about Slack so far is absolutely free, no matter the size of the company or group. Slack is betting that you’ll find it to be a vital tool for your work, and upgrade to a paid plan for just a few more options: the ability to search the entire history of conversations (the free plan saves only the last 10,000 messages), for example, or to implement specific privacy and security settings required by larger companies.

Slack is definitely finding its market, with 85,000 teams paying over $350 million a year. With a direct listing to go public June 20, the company is valued at about $17 billion.

But its free offerings are more than enough for most small businesses, and Slack works great for soccer teams and study groups, too.

If you’d like to try Slack before introducing it to your co-workers or friends, check out HawaiiSlack.com, a general purpose Slack group for locals.

And if you’re not ready to give up email, next month I’ll tell you about a simple tool that can turn your email inbox into a powerful time and task management hub.

Ryan Ozawa is communications director for local tech company Hawaii Information Service, and a lifelong technologist. You can follow him on Instagram and Twitter at @hawaii.