As of Tuesday, March 21'st 2023, CR has been retired and replaced with a new Energy System. Review this article if you are curious about how the prior system functioned.
Previously, you could hover over the SPS icon shown next to your username in order to see your Capture Rate.
The Capture Rate (CR) displayed as a percentage. This percentage was an important factor in calculating the SPS earnings of a ranked battle. So playing at a high Capture Rate made you earn more SPS per battle. The Capture Rate also impacted your reward shares (which consist of season points and focus points) .
Your CR depleted 1% per ranked battle, whether you win or lose. The CR regenerates 25% per passing day (= about 1% per hour). The maximum amount of ECR is 100%.
Note: since the update of 7/21/2022 CR dropped 5% per battle if you start a battle at or below 50% CR.
Hovering over the pointed (i) mark after any battle allowed you to see what particular percentage your capture rare was for the battle.