Adding a small pinch of salt to coffee grounds before brewing is an old folk technique, and unlike a lot of brewing lore, it has a genuine, well-understood chemical basis behind it rather than being pure myth.
What salt actually does
Sodium ions interact with the taste receptors on your tongue in a way that suppresses the perception of bitterness, the same basic principle behind salting bitter foods like grapefruit or dark chocolate to make them taste sweeter and rounder. It doesn't remove bitter compounds from the coffee itself, it changes how your palate perceives them.
When it's actually useful
This technique is most useful as a rescue for a cup that's already slightly over-extracted and tasting harsher or more bitter than intended, it won't fix a genuinely bad or stale coffee, but it can round off the edges of an otherwise decent cup that went a touch too far.
It's less necessary, and arguably pointless, on a coffee that's already well-extracted and balanced. If your brewing is dialled in, there's nothing bitter left to soften.
How to try it
Add the smallest pinch you can manage, less than an eighth of a teaspoon per cup, directly to the dry grounds before brewing, not to the finished cup. Taste before adding more. If you can taste salt at all, you've added too much.
A folk technique with real chemistry
Plenty of brewing lore doesn't hold up to scrutiny, but this one does, sodium suppressing bitterness perception is well-established outside coffee too. It's worth trying once on a cup that tastes a little harsher than you'd like, more as an occasional fix than a habit to build into every brew.
The takeaway
A pinch of salt is a real, chemically grounded way to soften perceived bitterness in an over-extracted cup, not a myth, but not a substitute for getting the brewing right in the first place either.
