In most readings the web does the work, standing for something the dreamer has built patiently, while the spider stands for the patience that keeps it up.
What carries the meaning here is usually the web rather than the animal sitting on it. Interpreters read the web as something the dreamer built slowly and is still maintaining: a household, a business, a set of obligations that holds together because somebody keeps repairing it. The spider, on that reading, is the patience itself.
The image flips depending on whose web it is. Dreamers who describe watching a spider work, or finding a web lit up with dew, generally come away with a sense of craft and competence. Dreamers who describe walking into one in the dark, or finding themselves stuck, are working with the opposite gloss, and the old lists take that as an arrangement entered without noticing how hard it would be to leave.
A very large spider is not automatically a bigger version of the same meaning. Reports of enormous ones are strongly associated with fever, with sleep paralysis and with the half-waking state where the mind places a shape in the corner of a real bedroom. That is worth knowing before treating the size as symbolic. Where the setting is a house, corners and ceilings tend to stand for the parts of a life that get looked at least often.
Spiders are the animal most people genuinely encounter indoors, and often the last living thing seen before a lamp goes off. Daytime attention shapes what the night reuses, so the picture can arrive carrying no meaning at all.
Fear is worth separating from symbolism too. If you grew up somewhere a particular spider was actually dangerous, the dread in the dream is a fact about your surroundings rather than a message about your life.


