What is high-altitude adjustments?

Above ~3,000 ft / 900 m, atmospheric pressure drops and dough rises faster (gas expands more) and dries out quicker. Typical adjustments: reduce yeast 15-25% (less is more — watch the dough, not the clock), increase liquid 1-2 tbsp per cup of flour, and shorten fermentation times. Above ~5,000 ft / 1,500 m these effects compound — King Arthur publishes a dedicated altitude baking guide worth consulting. The library defaults assume sea-level conditions.