Same active ingredient, completely different job. Here's when to use which.
A lot of wet shavers ask: "If I already use an alum block, do I need styptic powder?" Yes — they do different jobs.
Alum block: a post-shave antiseptic. You rub the wet block across your whole face after rinsing. It's astringent, mildly stinging, and a great way to close pores and disinfect.
Styptic powder: a targeted clot-stopper. You apply it directly and only to a nick or cut. It works much faster than a block.
The verdict: They're complementary. Many wet shavers keep both — block on the shower shelf for the whole-face post-shave, tin on the counter for targeted nick treatment. Different tools, same heritage ingredient.