Rocket League introduced Credits as its premium currency with the Blueprint system. Credits replaced the game’s former Keys and were used to build items from Blueprints.
The change arrived in December 2019, when Psyonix replaced randomized Crates with Blueprints that revealed the specific item available. Players could then spend Credits to create that item, rather than buying a key to open a crate without knowing the result.
Credits also became useful beyond Blueprints: players could spend them in the Item Shop, upgrade to Rocket Pass Premium, or trade them under the game’s trading rules. The conversion rate for old Keys varied by inventory size, ranging from 100 to 130 Credits per Key. Coins and Tokens are not the canonical answer; Esports Tokens are a separate currency for the Esports Shop.