The Short Answer: Four Things to Check
How to tell if an apple is ripe comes down to four quick checks you can do right at the tree. First, look at the background color of the skin — the part that isn't red or streaked. On most varieties, that base color shifts from green toward yellow or creamy white as the fruit matures. Second, squeeze gently. A ripe apple should feel firm but not rockhard; slight give under real pressure is okay, but anything soft or mealy is past peak. Third, try the twist test: cup the apple in your palm and give it a gentle quarter-turn upward. If it separates cleanly from the branch with almost no force, it's ready. If you have to tug or the stem breaks, give it a few more days. Fourth, smell it. A ripe apple has a noticeable sweet, fruity aroma right at the skin. An unripe one smells like almost nothing.
That's the whole framework. The rest of this post goes deeper on each check — and adds variety-by-variety timing so you know when do apples ripen for each type grown in Western NY.