Best Browser Games of 2016 (Slither.io Year)

2016 was the year the .io genre stopped being a one-game novelty and became a category. Slither.io launched in March, hit thirty-five million downloads inside four months, and topped the US App Store charts. Matheus Valadares released Diep.io in April. Mope.io showed up later in the year. Agar.io was still in its peak. The best browser games 2016 produced were almost all .io games — and that pattern shaped browser gaming for the rest of the decade.

1. Slither.io

Steve Howse released Slither.io on March 25, 2016. By the end of June, the game had been downloaded thirty-five million times across web and mobile. It topped the US App Store charts. Snake-as-MMO turned out to be exactly the right idea at exactly the right time. The browser version stayed the canonical experience. For our full take, see our Slither.io review.

2. Diep.io

Matheus Valadares followed Agar.io with Diep.io in April 2016. A top-down tank shooter with stat upgrades, evolving classes, and multiple modes. Where Agar.io had been about pure growth, Diep.io added build choices, role specialization, and competitive depth. It became the deepest .io game on the web and stayed that way for years.

3. Agar.io

Year two of Matheus Valadares’ founding .io title was still a strong year. Agar.io had been the breakout of 2015, and 2016’s audience extended that. The cell-eating loop — eat smaller cells, dodge bigger ones, grow toward the top of the leaderboard — kept new players coming in. Agar.io was no longer the only .io game on the block by mid-2016, but it was still the one most people had played first.

4. Mope.io

Justin Lyttle launched Mope.io in 2016. The animal-evolution survival game gave players a longer match arc than Slither or Agar — start as a shrimp, eat algae, evolve into bigger and bigger animals, eventually reach dragon. The depth-of-progression element distinguished Mope from the pure-growth .io games and built a strong long-tail audience.

5. Cookie Clicker

Three years old in 2016, Cookie Clicker still received regular content updates. The 2016 patches expanded the ascension system and added new building tiers. The game had moved past its 2013 viral moment but had become the canonical incremental — the one people pointed to when explaining the genre.

6. A Dark Room

Doublespeak Games’ minimalist survival narrative was three years old in 2016 and kept finding new players. The slow reveal — one button, then ten, then a world, then a devastating ending — was impossible to spoil, which is why discovery kept happening years after launch.

7. Wings.io

The fighter-plane .io game launched in 2016 and built a solid player base. Air-to-air combat, upgradable aircraft, weapon pickups. Wings.io was less famous than Slither or Diep but mechanically distinct enough to carve out its own audience.

8. The Chrome Dino game

Sebastien Gabriel’s offline endless runner was two years old in 2016 and embedded in every Chrome install on Earth. By total session count, almost certainly the most-played browser game of the year — people hit it whenever their Wi-Fi blinked. A clean version of the T-Rex Runner is right at the top of this page if you want to play without simulating a network outage.

9. QWOP (browser-playable)

Bennett Foddy’s deliberately punishing track-and-field game from 2008 stayed popular through 2016 on the browser. The Q-W-O-P keyboard control scheme — one key per leg muscle — made finishing a 100-meter race a genuine accomplishment. The game continued to inspire YouTube content years after launch.

10. Cubefield

Max Games’ 2007 endless cube-dodging game was nine years old in 2016 and still on every “unblocked games” portal. Pure reflex gameplay — steer a triangle through an endless field of cubes that gets progressively faster. Cubefield’s longevity is the kind of thing that happens when a game does one thing perfectly.

11. Town of Salem

BlankMediaGames’ social deduction MMO continued to grow through 2016. The 15-player role-based Mafia-Werewolf hybrid built one of the most engaged browser-game communities of the mid-2010s. Town of Salem predated the Among Us social-deduction boom by years.

12. Realm Grinder

Divine Games’ faction-based incremental had launched in 2015 and was mid-pack by 2016. The choice of good, evil, or neutral factions with branching mechanics gave the game a structural depth most clickers didn’t bother with. Long-term players were starting to reach the prestige tier.

13. Stick War 2

The sequel to the original Stick War (2009) was running in browser portals throughout 2016. Real-time strategy with stick-figure armies, multiple unit types, base-building. Stick War 2 was the genre’s accessible entry point — closer to a Flash classic than a 2016 release, but still pulling fresh players.

14. Universal Paperclips (almost — pre-2017)

Frank Lantz’s clicker-with-philosophical-payload wouldn’t actually launch until September 2017, but the concept was kicking around the games-research community in 2016. We mention it as a marker — 2016 set up the conditions that made Paperclips possible.

15. Bonk.io

Chaz Romalia’s physics-based ball-arena game launched in 2016 and built a quiet but consistent audience. Two-to-eight player ragdoll arenas with customizable maps. Bonk.io was a smaller .io success that didn’t get the Diep/Slither headlines but stayed playable for years.

The Slither.io year

2016 was the year browser gaming proved it could produce hits at the scale of mobile blockbusters. Slither.io’s thirty-five million downloads in four months wasn’t normal browser-game numbers — it was the browser briefly competing with the App Store on equal terms. The game ran in any tab, no install required, with full multiplayer matchmaking that worked across continents.

The .io explosion that year — Slither in March, Diep in April, Mope later, Wings, Bonk, and dozens of clones in between — set the template for the rest of the decade. Free-to-play, multiplayer-first, no install, two-minute sessions. Every browser-game studio after 2016 had to either compete with that template or work around it.

What didn’t make 2016 lists

Wordle (2021), Among Us (technically 2018 but didn’t blow up until 2020), and the post-2020 wave of NYT puzzle games didn’t exist in 2016. Universal Paperclips would come in 2017. The defining hits of the late-2010s and early-2020s were still future games as of 2016.

Frequently asked questions

When did Slither.io launch?

Slither.io launched on March 25, 2016, by Steve Howse. It hit thirty-five million downloads across web and mobile in its first four months and topped the US App Store charts that spring and summer.

When did Diep.io launch?

Diep.io launched in April 2016, developed by Matheus Valadares, who had previously created Agar.io. It became the deepest .io game on the web and remained popular for years.

What was the biggest browser game of 2016?

By downloads and active players, Slither.io was the year’s defining hit. By total session count, the Chrome Dino game wins on browser distribution. By depth of gameplay, Diep.io held the top slot.

Was Mope.io launched in 2016?

Yes. Justin Lyttle released Mope.io in 2016. The animal-evolution survival game added longer-arc progression to the .io formula and built a strong audience through the year.

Was Agar.io still popular in 2016?

Yes. A year after its 2015 launch, Agar.io was still pulling significant daily player counts. It was no longer the only .io game on the block but remained the genre’s flagship simple-and-accessible entry point.

The takeaway

2016 was the year the browser produced a hit at App Store scale. Slither.io did the impossible — a free browser game that beat paid mobile titles on the same charts. Diep.io and Mope.io showed the genre had depth as well as reach. For an evergreen browser loop from the same era, the dino game at the top of this page is the quiet year-2016 standard that’s still running in 2026.