Kosher symbols are small trademarks, called hechsherim, that certifying agencies print on food to show a product meets Jewish dietary law. The best known in the United States is the OU, a letter U inside a circle, run by the Orthodox Union (oukosher.org). Each mark belongs to a named agency, and the letter beside it tells you what you can eat the food with. Want to skip the label and check a specific fish instead? You can look up any fish in seconds with the KosherFish tool.
What a kosher symbol actually is
A hechsher is the trademark of the agency that certified a food, not a generic stamp anyone can print. In Hebrew the word means approval. Behind every hechsher sits a real process. Companies hire a kosher certification agency, which checks the ingredients, inspects the equipment, and supervises the production runs. Only then does the agency license its symbol for the label.
That makes the mark a promise from a named organization that a trained rabbi or mashgiach verified the food against the laws of kashrut. Does the agency really matter that much? Yes. Trust depends on the certifiers behind a symbol. Reliable hechsherim name exactly who stands behind the food, so you can weigh their standards. An anonymous mark tells you nothing.
The major kosher symbols and who runs them
Five agencies certify most of the kosher food sold in the United States. Known as the big five, they are the Orthodox Union (OU), OK Kosher Certification (OK), Star-K, Kof-K, and the Chicago Rabbinical Council (cRc). These certifiers meet high standards and are accepted across most observant communities. Among them, the OU is the most widely used kosher symbol in the world and appears on tens of thousands of products.
| Symbol | Agency | What it looks like |
|---|---|---|
| OU | Orthodox Union | A letter U inside a circle |
| OK | OK Kosher Certification | A letter K inside a circle |
| Star-K | Star-K Kosher | A letter K inside a star |
| Kof-K | Kof-K Kosher Supervision | A K paired with the Hebrew letter kof |
| cRc | Chicago Rabbinical Council | The cRc lettermark |
Plenty of other reliable agencies operate regionally and overseas, so a symbol you do not recognize is not automatically a problem. One rule helps. Never confuse the OU with a plain U, or any circled letter with a bare one. The circle, the star, or the paired letters are the trademark. Spot a different mark you do not know? Check it against a published list of accepted agencies or ask your rabbi.
What the letters next to a kosher symbol mean
The letter or word beside a kosher symbol tells you the product’s status, which controls what you can eat it with. Per the Orthodox Union, here is what each code means (oukosher.org):
| Code | Means | What you can do with it |
|---|---|---|
| Pareve (or no letter) | Neither meat nor dairy, made on neutral equipment | Eat it with meat or with dairy |
| D | Dairy, or made on dairy equipment | Keep it away from meat |
| DE | No dairy ingredients, but made on dairy equipment | Essentially pareve, some avoid it right after meat |
| M (or Glatt) | Meat or contains meat | Keep it away from dairy products |
| F | Contains fish | Do not cook or eat it with meat |
| P | Kosher for Passover | Use during Pesach (OU-P also means pareve) |
One letter trips people up more than any other. P does not mean pareve. P means kosher for Passover. The Orthodox Union notes its own OU-P symbol means a product is both kosher for Passover and pareve, but the P itself stands for Passover (oukosher.org). Pareve is shown by the word pareve, or by a plain symbol with no D or M next to it.
DE causes confusion too. The code means a product has no dairy ingredients but was made on equipment also used for dairy. The OU treats it as essentially pareve, though some keep the custom not to eat a DE product right after a meat meal. An F or the word fish flags fish, and that mark earns its own letter for a reason. Kosher fish counts as pareve, yet a long-standing custom holds that you do not eat fish together with meat, so a fish product should not be cooked or served with meat. Our guide on what makes a fish kosher covers the fins-and-scales rule in full.
Kosher symbols and the meat-and-dairy rule
D and M letters exist because kashrut keeps meat and dairy completely separate. The Torah’s rule against cooking a young goat in its mother’s milk (Exodus 23:19) is the source, and the practice grew to forbid cooking or eating meat and dairy together. So that single letter does real work in a kosher kitchen.
An OU-D product contains dairy, or ran on kosher dairy equipment, so you keep it away from a meat meal. Meat marked OU-M stays away from milk and dairy. A plain symbol, or the word pareve, means neither, so it works alongside either group. This is also why kosher kitchens keep separate dishes, pots, and equipment for meat and dairy. While you shop, that little letter is how you sort each product into the right category.
Why dairy-free shoppers read kosher symbols
Many shoppers who do not keep kosher still read these symbols. If you avoid dairy for an allergy, for lactose intolerance, or on a vegan diet, a pareve mark is a quick signal that a food is free of milk and dairy. A plain OU, or the word pareve, means the product contains no meat and no dairy ingredients at all.
Read OU-DE with a little more care. The code means a product has no dairy ingredients but was made on dairy equipment, so a trace is possible. Anyone with a severe milk allergy should still read the full ingredient list, because kosher status tracks Jewish law, not allergen limits. As a fast label check for dairy, though, the pareve symbol is hard to beat, which is why so many dairy-free consumers now scan for a hechsher.
Why a plain letter K is not a kosher symbol
A plain letter K is not a reliable kosher symbol, and the reason surprises most people. The letter K cannot be trademarked, so any company can print a bare K on a package without rabbinic supervision. The OU puts it plainly. On its own, a K tells you nothing about who, if anyone, is certifying the food (oukosher.org). OK Kosher makes the same point, that a standalone K carries no legal or halachic guarantee (ok.org).
Here is the fix. Symbols inside a circle, inside a star, or paired with another letter are registered trademarks that belong to a specific agency. A naked K is not. Spot a bare K? Find out which agency, if any, stands behind it before you rely on it. When unsure, treat an unverified K as uncertified.
How kosher symbols apply to fish
Kosher fish follow the same certification logic, with one rule that comes straight from the Torah. A fish is kosher only if it has fins and scales that lift off without tearing the skin (Leviticus 11:9-12 and Deuteronomy 14:9-10). Whole fresh fish with the skin and scales still attached usually does not need a hechsher, because you can see the kosher signs with your own eyes.
Things change once the fish is filleted, smoked, canned, or ground into something like gefilte fish. With the identifying scales gone, a kosher symbol becomes the practical way to confirm both the species and that the equipment was kosher. That is where a mark like the OU, or an F fish designation, earns its keep. To learn whether a particular fish is kosher in the first place, scan the full kosher fish list or type the name into the lookup tool.
Check any fish with KosherFish
Reading a label is one job. Knowing whether the fish itself is kosher is another, and that is what KosherFish is for. You can look up salmon, tilapia, swordfish, and more than 290 other species on the full kosher fish list, each with a clear verdict and the fins-and-scales reason behind it.
At the fish counter or reading a restaurant menu, the iOS app and the Android app put the same lookup in your pocket, so you can check a fish before you buy it. A label tells you about the processing. KosherFish tells you about the fish.
Frequently asked questions
What do kosher symbols mean?
Kosher symbols are trademarks printed on food to show a certifying agency has verified the product meets Jewish dietary law. The symbol names the agency, like the OU for the Orthodox Union, and a nearby letter shows the status. D means dairy, M means meat, P means kosher for Passover, and a plain symbol or the word pareve means neither meat nor dairy.
What is a hechsher?
A hechsher is the kosher certification symbol of a supervising agency, and the word is Hebrew for approval. A company hires the agency, which checks ingredients, inspects equipment, and supervises production, then licenses its trademarked mark for the label. The hechsher is a promise from a named organization that a rabbi or mashgiach verified the food against the laws of kashrut, which is why the certifier behind it matters.
What does OU mean on food?
OU is the kosher symbol of the Orthodox Union, shown as a letter U inside a circle, and it is the most widely used hechsher in the world. A plain OU means the product is pareve. OU-D means dairy, OU-M means meat, and OU-P means kosher for Passover and pareve, according to the Orthodox Union. The circle is the trademark, so do not confuse it with a plain U.
Does P mean pareve on a kosher label?
No. The letter P means kosher for Passover, not pareve. This is the most common mix-up on kosher labels. The Orthodox Union notes its OU-P symbol means a product is both kosher for Passover and pareve, but the P itself stands for Passover. Pareve, meaning neither meat nor dairy, is shown by the word pareve or by a plain symbol with no D or M beside it.
Is a plain K kosher?
A plain letter K is not a reliable guarantee that a food is kosher. The letter K cannot be trademarked, so any company can print it without rabbinic supervision. The Orthodox Union and OK Kosher both warn that a lone K carries no legal or halachic guarantee. Find out which agency, if any, stands behind the K before you rely on it, and treat an unverified K as uncertified.
What does pareve mean?
Pareve, also spelled parve, means a food contains neither meat nor dairy and was made on neutral equipment. The Orthodox Union notes pareve foods can be eaten with either meat or dairy. Kosher fish, eggs, fruit, vegetables, and grains are pareve. One caveat: a custom holds that you do not eat fish together with meat, even though fish is pareve, so a fish product still should not be cooked with meat.
Do you need a kosher symbol on fresh fish?
Usually not. Whole fresh fish with the skin and scales attached does not require a hechsher, because you can see the kosher signs, fins and removable scales, yourself (Leviticus 11). Once fish is filleted, smoked, canned, or ground, the scales are gone, so a kosher symbol becomes the practical way to confirm the species and the equipment. When in doubt, look for a reliable certifier’s mark or check the species first.
The bottom line
A kosher symbol is the trademark of a supervising agency, and the letter beside it sorts the food into a category. Learn the big five (OU, OK, Star-K, Kof-K, and cRc), read the codes (pareve, D, DE, M, F, and P for Passover), and treat a bare K with caution. For anything you are genuinely unsure about, check a reliable certification or ask your own rabbi. KosherFish is an information and lookup tool, not a posek, so it helps you find the answer rather than rule on the dietary laws.
When the question is the fish itself rather than the label, start with what makes a fish kosher, browse the most common kosher fish, or see how processing changes things in our guide to whether imitation crab is kosher. Then check any species on the full kosher fish list, type a name into the lookup tool, or keep it in your pocket with the iOS app or Android app.