Why do screws keep pulling out of my plasterboard walls?
Because plasterboard is a soft gypsum core between two layers of paper, and it has almost no capacity to hold a thread. A screw driven straight into it grips only a thin section of crumbly material, which crushes under load and lets go. The board is a surface, not a structural fixing point.
The correct approach depends on what you are hanging. For anything heavy — shelves, wall-mounted televisions, kitchen cupboards, handrails — find the timber or metal studs behind the board and fix into those. Studs are typically at 400mm or 600mm centres, and a stud detector or a careful tap test will locate them. A screw into solid timber is many times stronger than anything fixed to the board alone.
When a stud is not where you need it, use a fixing designed for hollow walls. Plastic expanding plugs sold for masonry are the wrong tool and are a very common mistake — they spin in the hole. Spring toggles and butterfly toggles open out behind the board and spread the load across a wide area, and they carry the heaviest loads of the hollow-wall options. Metal self-drilling anchors screw directly into the board and are convenient for light to medium loads such as picture frames and small shelves. Rubber sleeve anchors compress behind the board and cope well where the board thickness is uncertain.
Spreading the load matters as much as the fixing itself. Two fixings well apart carry far more than one, and a shelf bracket screwed at top and bottom resists the leverage that pulls fixings out.
If a hole has already failed, do not simply put a larger screw in the same place — move across, or fit a repair patch first.