A fish is kosher only if it has both true fins and true scales. That is the whole rule, and it comes straight from the Torah: “Whatsoever hath fins and scales in the waters… them shall ye eat” (Leviticus 11:9).
What counts as a scale #
Not every scale qualifies. A kosher scale has to be visible to the eye and removable without tearing the skin. Scales that are fused to the skin, or that rip the flesh when you pull them off, do not count. This is why some fish that look scaly are still not kosher.
Why scales are the deciding factor #
Almost every fish has fins, so fins rarely settle the question. Scales do. The accepted rule is that any fish with the right kind of scales also has fins, so in practice you are really checking for scales. KosherFish shows both on every page so you can see the full picture.
No blood-related rules to track #
Fish are simpler than meat and poultry here. There is no requirement for ritual slaughter, and fish is not mixed with the meat-and-dairy separation rules. Once a fish passes the fins-and-scales test, the species is permitted.
This is the rule behind every verdict on the site. The rest of this section covers the cases people find confusing.
