Achievements

Achievements are one of the main ways to track progression in Cookie Clicker. As of 2.031 there are 518 regular achievements, 16 shadow achievements, and 4 dungeon achievements only obtainable in the Dungeons beta. Achievements are unlocked in a variety of ways and increase the potency of the players' kitten upgrades (except for shadow achievements). Every 25 achievements, the player unlocks a new cosmetic color for the Milk displayed under the Big Cookie.

Strategy
Since kitten upgrades are some of the most powerful boosts to cookie production, keeping an eye on obtainable achievements is always a good idea. Some achievements are not usually obtained during normal gameplay, so dedicating a bit of time to getting achievements can be very worthwhile. Achievements are also one of the features of the game that permanently carry over between ascensions.

For players who want to be very efficient, getting both Neverclick and Hardcore before the first ascension is worthwhile. Getting these achievements will take the same amount of time in any point of the game due to requiring an ascension in the born again challenge mode. This means that unlocking them on the first ascension is moderately faster than doing them at any later point in the game. However, this strategy is not necessarily the best for new players as it's very far from being representative of the actual game and getting these achievements efficiently requires a moderate understanding of game mechanics.

There are a few achievements that can be easily obtained when starting a new game. Tiny cookie, What's in a name, Here you go, Tabloid addiction, and Uncanny clicker do not have any gameplay requirements. Cookie-dunker only requires having three prior achievements and Wake and bake is obtained when clicking the cookie once. A possible way to start a new game is by obtaining all of these achievements. Although this does not give any immediate benefit, it's an easy way to get a head start.

Kittens only count the number of achievements a player has, so the milk tiers are purely cosmetic. Achievements do not have to be unlocked in increments of 25 to have an effect on how powerful the kittens are. If the player has kittens, any achievement will give an increase in cookie production. One of the many benefits of buying lower tier Buildings is that buildings have associated achievements every 50 levels which increase how powerful milk is.

Since the Reincarnation achievement will usually not be obtained by normal gameplay, it's advisable to do it in one series of ascensions at the optimal prestige level (about 1 trillion). This achievement is harder to obtain both early and late into the game. Getting it early is hard because having more heavenly chips and upgrades speeds up cookie production drastically. However, the amount of cookies baked required to earn a single heavenly chip also increases disproportionately in the late game. The general guideline is that the fastest ascensions take around ten seconds, so if getting to a single heavenly chip in an ascension is taking around ten seconds, it might be the right time to get this achievement.

The last achievements most players get are ones associated with using sugar lumps to upgrade building levels. This is because getting each one of these achievements requires a total of 935 sugar lumps. Without any exploits and relatively idle play, obtaining this amount of sugar lumps will take around two years. The speed of accumulating them can be drastically sped up by using the Garden, but this still requires around a year of gameplay when not using any exploits. The garden can also be used to speed up Black cat's paw, as ordinary clovers and golden clovers provide a significant boost to the rates at which Golden Cookies appear.

Moistburster and Reindeer sleigher have to be obtained in a single ascension. Getting Moistburster is made a lot easier by having the Unholy bait heavenly upgrade, and can also be significantly sped up by using Skruuia in the Pantheon and being in stage 3 of the grandmapocalypse. In normal gameplay, wrinklers should only be sparsely bursted, so it's a good idea to get this achievement at the end of an ascension.