The container size is about the container, not the amount used
A nearly empty bottle that is still labeled or sized above the typical limit is usually treated the same as a full one — screening is based on container size, not how much liquid is actually inside it.
Why the limit exists at all
The rule exists to keep any single container small enough that its contents can be reliably screened or deemed low-risk by volume, not because small amounts of liquid are inherently safe and large ones are not.
Exceptions exist, but need separate handling
Medically necessary liquids and some baby-care items are commonly treated as exceptions, but typically need to be declared separately at screening rather than packed in with everything else and hoped past unnoticed.
Questions people ask
Does the liquids rule apply to solid-to-liquid items like gels?
Yes — anything that can be spread, poured, sprayed, or pumped is generally treated as a liquid for screening purposes, regardless of its texture.
Can I buy liquids past security and bring them on board?
Generally yes, since those purchases happen after screening, though connecting through additional security checkpoints can complicate carrying them further.