Yosemite Decimal System

The Yosemite Decimal System (YDS) is a way to rate the difficulty of hiking and climbing routes. It uses a combination of numbers and letters: the number indicates overall difficulty (like 5.0 to 5.15+), and the letter 'a' to 'd' provides finer detail within that level. For example, 5.10a is more challenging than 5.8. The system helps adventurers assess route complexity, technical difficulty, and risk. It’s primarily used for rock climbing but also for some hiking trails, guiding climbers and hikers in choosing routes suitable for their skill level.