Attention: If anyone knows advanced strategies for specific tier 10s, please let me know! I am making a separate guide for more advanced players! :D
2016:
Deeeep.io is released, with the following animals:
Clownfish, Crab, Squid, Seagull, Ray, Beaver, Hammerhead Shark, Dolphin, Shark
Update 1:
When evolving, the player is shown information about the animal.
A small oxygen bar now appears below the HP bar on the animal. It turns red when oxygen is low.
The oxygen limit for beavers and dolphins has been increased.
Dam food has been added.
Animation for eating is smoother.
Update 2:
Players no longer glitch out of the map.
Update 3:
Players can now respawn with decreased XP rather than having to restart. This does not work across servers.
Update 4:
Servers for South America, Europe, and Asia have been added.
Update 5:
The map size has been tripled.
The player limit has increased to 100.
Seagulls and islands have been added. Crabs and beavers can now walk on islands.
Update 6:
Chat can now be toggled on and off with the "M" key.
Update 7:
Orcas and whales have been added.
Update 8:
Whales are now immune to suction.
Lag has been decreased.
Update 9:
Arctic biome has been added.
Jellyfish and penguins have been added.
Players can now log in to the game.
Update 10:
Jellyfish damage and speed is reduced.
Whales can no longer absorb beavers.
Jellyfish now take less recoil.
If an animal takes a fatal hit from another animal, the attacker no longer takes recoil if the attacker is 3+ tiers higher than the victim.
Players are invulnerable for 5 seconds after spawning or respawning.
Screen now flashes red when taking damage.
Penguin now has three boosts bars.
XP required for each tier has been decreased.
Food no longer stops appearing.
Update 11:
Whales can now damage each other.
Animals that a whale absorbs do not take temperature damage if they are carried into the wrong biome.
Seagulls need less XP to level up.
2017:
Update 1:
North America now has three additional servers.
Europe and Asia both have an additional server each.
Update 2:
Sharks, whales, and orcas are now the same tier.
The evolution tree now branches.
Map size has increased by 33%.
Igloos have been added. They are found on icebergs and penguins can hide in them.
Update 3:
The chat now censors curse words.
Update 4:
The Deeeep.io Discord (Deeeepcord) has been created!
Update 5:
The XP bar now shows progress towards the next tier.
Boost damage has been decreased to +25% of the default damage (except shark).
Animals no longer turn slowly (except shark's ability)
Crabs now have 50% more HP.
Penguins now have two boost bars.
Sharks can no longer eat food other than meat while boosting.
Orcas are slowed when they grab an animal. The bigger the animal, the slower the orca while grabbing.
Update 6:
Deeeep.io has now been translated into Croatian/Serbian, French, Italian, Finnish, Swedish, Turkish, Dutch, Polish, Arabic, German, Czech, and Estonian.
Update 7:
Deeeep biome has been added.
Blobfish, worms, king crabs, anglerfish, and leopard seals have been added.
Update 8:
Clownfish now get a +10% speed boost for every other clownfish they swim with. The highest speed is +50%.
Update 9:
Sea turtles and oarfish have been added.
Update 10:
The game now automatically picks the server with the least lag by default. Servers can still be chosen by players.
Update 11:
Octopi, narwhals, cachalot, and giant squid have been added.
Update 12:
Orcas now take recoil when releasing an animal. Spinning before releasing reduces recoil.
Update 13:
If a player logs in, they can share screenshots of their gameplay when they die.
Update 14:
Lampreys, pelicans, marlins, polar bears, and whale sharks have been added.
Update 15:
Stonefish and sunfish have been added.
Update 16:
Pearl Defense has been added!
Update 17:
Swamp biome has been added.
Piranhas, frogs, electric eels, snapping turtles, manatees, crocodiles, hippos, and eagles have been added.
Update 18:
Hacking the game is more difficult
Update 19:
Bobbit worms, mahi mahis, mantis shrimp, frilled sharks, sawfish, and walruses and have been added.
Update 20:
When evolving from clownfish, players lose their speed boost.
Update 21:
Manta rays have been added.
Toxic Algae has been added!
Players can now spectate the game.
Update 22:
Spectators can no longer enter manta ray auras.
Update 23:
1v1 has been added!
Update 24:
Spectators can no longer spawn food by pressing "E".
2018:
Update 1:
Icefish, giant isopods, flying fish, catfish, little auks, barreleyes, seals, ducks, pufferfish, gulper eels, sea lions, dragonfish, lionfish, Humboldt squids, anacondas, sleeper sharks, elephant seals, tiger sharks, and goblin sharks have been added!
2020:
Update 1:
Blind cavefish, climbing cavefish, crayfish, axolotls, giant salamanders, and humpback whales have been added.
Electric eel is now a tier 9 animal.
Update 2:
Reef biome has been added.
Barracudas, thresher sharks, leatherback turtles, wobbegong sharks, moray eels, colossal squids, lobsters, Atlantic torpedoes, basking sharks, archerfish, horseshoe crabs, frogfish, and coconut crabs have been added.
Update 3:
Bull sharks have been added.
Food glows in the deeeep.
Shark boost now has a delay before taking effect.
The slow debuff only halves animals' boost distance if the slow is -30% or higher.
Update 4:
Hermit crabs and shells have been added.
Shark boost no longer has a delay but uses a charge boost.
Bull shark can no longer boost instantly after boosting into an animal. It now has increased HP and armor penetration.
Humpback whale's blast song now knocks animals back further, but has less stun duration. Humpback whale's speed song lasts less time.