A good white shirt is less about a perfect standard and more about the relationship between fabric, fit and use. Before choosing one, decide whether you want a crisp tailored look, a soft relaxed layer or something that can do both.
Check the fabric in daylight
Hold a single layer up to the light to assess transparency. Cotton poplin often has a smooth, crisp appearance, while a textured weave or a blend can feel different against the skin. Fibre content alone does not tell you everything: fabric weight, finish and construction also matter. In the United States, most textile products must include fibre content on their labels; requirements vary elsewhere.
Try the details
Button the shirt and sit, reach forward and lift your arms. Look for pulling across the chest or back, and check that the collar and cuffs are comfortable. Examine the stitching around buttons and buttonholes. An intentionally loose shape should still allow the shirt to stay where you want it when you move.
Consider care
Read the washing instructions before buying and decide whether ironing fits your routine. Compare the shirt with clothes already in your wardrobe. A slightly sheer shirt may work well as an open layer, while a heavier one may be better if you prefer more coverage.