Why these aren't all 1:1
Butter is roughly 80% fat and about 15-17% water, with the rest milk solids — that composition is what gives baked goods their structure, flavor, and texture, and no substitute matches it exactly. Oil is 100% fat with no water, so recipes typically call for slightly less oil (about ¾ the volume) to avoid an overly greasy result. Applesauce is mostly water and fiber with almost no fat, so it cuts richness substantially — great for health-conscious quick breads, poor for anything wanting a rich, tender crumb like shortbread or classic butter cookies. Solid coconut oil is the closest match in fat structure and solid-at-room-temperature behavior, which is why it's the one true 1:1 swap on this list.
Where each substitute works best
Oil substitutes work well in quick breads, muffins, and brownies where a slightly denser, moister crumb is fine or even desirable — but avoid it in recipes relying on creaming butter with sugar (classic cookies, pound cake), since oil can't trap air the way solid butter does during creaming. Applesauce and Greek yogurt both work best in moisture-forward bakes (muffins, banana bread) and both cut calories/fat meaningfully — but neither will give you a crisp cookie edge or a flaky pastry texture, since both lack butter's fat structure entirely.
FAQ
Will my cookies still spread and crisp with a substitute? Generally no — oil-based substitutes make cookies spread more and stay softer/chewier rather than crisping, since butter's water content (which turns to steam and helps set structure) isn't replicated.
Can I substitute for pastry/pie crust? Not well — pastry relies on solid butter's ability to create flaky layers when it melts in the oven; none of these substitutes replicate that mechanism, so a true 1:1 fat swap (like solid coconut oil) is the only reasonable option here, and even that changes flavor.