Google loves to unveil a good gag product on April Fool's Day. Remember 8-bit maps? YouTube DVDs?

But despite arriving on April 1, 2004, its webmail service was no joke. Google's simple, browser-based inbox helped seed several ideas that have become so commonplace over the intervening decade, they practically define modern computing as we know it.

Gmail debuted as an invitation-only product, forcing us to beg friends with newly minted gmail.com addresses for precious invites. And once we were in, we experienced something miraculous – a spam-free inbox with a killer integrated search tool and a gigabyte of gratis storage.

We already had webmail, but it was viewed mostly as a convenience to be used while on the road since we could access it from any computer. It wasn't enjoyable. Web inboxes were slow and cumbersome, messy with checkboxes and radio buttons, and often so riddled with spam they had to be emptied frequently lest they reach capacity.

Gmail changed all that. It was fast and elegant. There was so much storage, you never had to delete anything. In fact, you couldn't. There wasn't even a Delete button! And you didn't miss the Delete button, because the inbox was almost entirely spam-free.

What's more, it was built using Ajax, a JavaScript hack that lets webpages update without reloading and that doesn't require any plug-ins. Ajax had been kicking around on the web's bleeding edge for a couple of years. Microsoft had begun using it to dynamically display stock quotes inside Internet Explorer. But most websites still lacked any sort of dynamic interactivity. Before Ajax, users would click a link or a button on a webpage, and then they'd have to wait for the entire page to reload in order to see the result. Using Ajax, web programmers could build an application that redrew pieces of the page on the fly without having to reload the whole thing. A user could see new elements appearing and disappearing on the page as they clicked, minus all the waiting.

Gmail took Ajax mainstream. It gave webmail a slick snappiness more akin to a desktop application, and it left clunky old Hotmail in the dust. New messages just appeared, chat windows popped up instantly — all without a browser refresh. Today, we all expect websites to behave like real applications.

Another concept made familiar by Gmail: trading privacy for services. Skeptics objected to Google machine-reading our emails to improve its ad-targeting science, but the rest of us didn't care. After all, Gmail did so much, and it didn't cost a dime.

When the service finally went no-invites-required in February 2007 and opened to everyone, its user base quickly ballooned to tens of millions. Today, it's around half a billion. The service has also grown into a full-fledged platform. There's a contact manager and fully integrated text, video and SMS chat. Users can plug in widgets that help manage tasks, set reminders or just show pictures of their kids. Google has built up an entire suite of office applications that run in the browser, and Gmail is the hub.

And that brings us to the final big idea that Gmail popularized: cloud-based services.

Yes, cloud computing has always been a thing. The idea of storing data on a server and accessing it over the internet is older than your first SCSI drive, and it wasn't until recently that it acquired a fancy new buzzword. But Gmail put all the key concepts of cloud computing — a service delivered over the network, flexible mass storage, instant access from anywhere — into a consumer product that ran inside the web browser and behaved like a regular computer program. The idea that you could run Gmail at your desk at work, then go home and launch it on your desktop using a different browser, even a different operating system, and have it look and behave exactly the same way in both places was a totally new concept to almost everyone who used it. No special software was required. You never had to worry about storage. It was always there. And there were no messy connections, just a simple password login.

Today, all of these concepts — web applications, machine-targeted ads, cloud storage — are commonplace. Gmail was the arbiter. It may have not have exactly lowered the heavens upon its arrival, but it certainly ushered in the web's common era.

This article is adapted from two previously published pieces: one from issue 21.05 of WIRED magazine, and one that ran on this website on April 1, 2009.﻿