What about Shiny Pokémon, how do you catch those?
Shiny Pokémon are color variants. There exist a single color variation for every species of Pokémon; however, only some of the Shiny versions of Pokémon are available in Pokémon Go. With each event, more Shiny Pokémon are added, and sometimes they're added in at random.
The bad news is they're incredibly rare and they don't show up as Shiny on the map. You can't tell if a Pokémon is Shiny or not until youtap on it, and even if a specific Pokémon is Shiny for someone else, that doesn't mean it'll be Shiny for you. It's been theorized that there's only a 1/450 chance for a Pokémon to be Shiny outside of an event and for especially rare Pokémon, finding a Shiny can feel like winning the lottery.
The good news is, if you come across a Shiny Pokémon, it's no harder to catch than a regular Pokémon, and during events, Shiny Pokémon are much common. This is especially true on Community Day when the chances are closer to 1/25 of finding a Shiny Pokémon.
What are catch rates?
Pokémon Go works off a "random number generator" (RNG). Think of it like rolling dice in a board game. Any time something major happens, the Pokémon Go servers generate a random number to decide the outcome. Everything from which Pokémon spawns to whether you successfully catch it or it runs away is decided by the RGN.
When it comes to catching Pokémon, every Pokémon has a base "catch rate" or a percentage chance for you to catch them. That base catch rate is then multiplied by the Pokémon's level to get the actual catch rate at the time of your encounter. (Yes, just like trainers, Pokémon have levels.)
Some Pokémon, like Magikarp are much easier to catch with an approximate 70% catch rate. That means, by just throwing a regular Poké Ball without any curves or bonuses, there's slightly more than a 2 in 3 chance to catch it.
Other Pokémon are much more difficult to catch, like Articuno with an approximate 2% catch rate. That means, by just throwing a regular Poké Ball without curves or any other bonuses, there's only a 1 in 50 chance you'll catch them.
That number is then multiplied by the Pokémon's level. Basically, the higher the Pokémon's level, the harder it is to catch. In other words, low level Pokémon with high catch rates can be almost guaranteed to catch, while high level Pokémon with low catch rates could be almost impossible to catch.
Does the position of the Pokémon on screen make a difference?
Some Pokémon are right up in your face and easy to hit. Others, like Golbat or Ponyta hover or linger further away, making them harder to hit. Distance doesn't affect catch rate though. As long as you hit your target, you have the same chance to catch that target. And it's only once you hit it that catch rate matters.
Pro tip: If you're having trouble hitting a far-away Pokémon, switch to AR mode and tilt your screen. That'll bring them in closer and make them easier to hit.
What about your own trainer level, does that give you a bonus?
Not directly, but the higher your level the higher the level Pokémon you can encounter in the wild. So, while there are no bonuses as such awarded for being a higher level, you will come across Pokémon that are harder to catch as you level up.
Is catch rate x Pokémon level why some low CP Pokémon are so hard to catch? (?!)
It can be. When you a see a Pokémon on your catch screen you also see the CP (Combat Power) of that Pokémon. If the CP is low we tend to think the level is low, making it easier to catch. But CP doesn't just depend on level, it also depends on stats (IV).
So, a Pokémon with low CP could be a low level Pokémon with good stats or it could also be a high level Pokémon with lousy stats. In other words, if a low CP Pokémon keeps escaping your Poké Ball, odds are it's a lousy Pokémon that just happens to be high level and may not be worth your continued time and resources trying to catch.
What are flee rates?
Every Pokémon also has a base "flee rate". When a Pokémon escapes your Poké Ball, the dice get rolled again. If the random number generated is higher than the flee rate, they'll stay around and let you try to catch them again. If it's lower, they'll disappear in a puff of smoke and frustration.
The big difference between catch rates and flee rates is that, while catch rates can be modified down by Pokémon level and up by catch bonuses, flee rates are always the same. So far, in the game, nothing alters them.
Currently, the lowest flee rate is 5%. That means, if you catch one of those, there's only a 1 in 20 chance they'll flee. Counterintuitively, some of the most highly evolved and powerful Pokémon have the lowest flee rate, including Dragonite, Alakazam, Venusaur, Charizard, Blastoise, and many more.
Generally speaking, though, almost all Pokémon fall under 15%. Also counterintuitively, the ones at 20% are the Pidgey, Rattata, Zubat, and other most-common spawns. (That's why they feel like they run so often.)
The big outlier is Abra, which has a 99% flee rate. It's meant to emulate the way Abra would teleport away in the core Pokémon games and animated series, but it really means there's only a 1 in 100 chance Abra will stay around if you don't nail him with the first Poké Ball.
Is there a higher chance for a Pokémon to flee the more times it escapes?
Not really. The flee rate is always the same. The more times it escapes, though, the more often you risk it fleeing. So, if a Dragonite breaks free, it has a 5% chance of fleeing. If it breaks out again, the chance is still only 5%, but it's another chance. Same with the 10th or 20th breakout.
It's what makes super hard to catch yet low flee rate Pokémon so exciting/frustrating. You can throw every Ultra and Great Ball you have at a Dragonite and it can keep escaping yet never fleeing, draining you down.
Can Raid Bosses Flee?
Not in the traditional sense. You have to use Premier Balls to catch Raid Bosses and you only get those by beating the Raid Boss. You can keep trying to catch the Raid Boss as long as you have Premier Balls remaining. If it escapes the ball, it won't flee. But, if you run out of Premier Balls before you catch it, it will flee.
