Learning how to keep kosher is simpler than most people think. The Torah’s dietary laws, called kashrut, come down to a handful of rules: which animals you can eat, how they must be prepared, and which food combinations are off the table. This guide covers all of it, with particular attention to fish, because that’s where most questions land and where you can look up any species in seconds on KosherFish.
The Torah’s Foundation: What Kashrut Actually Requires
Kashrut (Jewish dietary law) is laid out in Leviticus 11 and Deuteronomy 14. The word kosher (Hebrew: כָּשֵׁר) means fit or proper. For Jewish families keeping kosher, it shapes every meal: what they buy at the grocery store, how they cook, which restaurants they can eat at, and how they equip their kitchen. The practice touches daily life from breakfast through dinner. Food that meets the Torah’s requirements is kosher. Food that doesn’t is treif.
The rules cover three areas: which animals, birds, and fish are permitted to eat, how you must slaughter and prepare permitted animals, and the prohibition on mixing meat and dairy. You don’t need to memorize every Talmudic detail to get started, but you do need to understand the three food categories, because they shape every practical decision in a kosher kitchen.
Meat, Dairy, and Pareve: The Three Kosher Food Categories
Every food in a kosher kitchen falls into one of three categories.
Meat (fleishig). Permitted land animals must have split hooves and chew their cud. Cattle, sheep, goats, and deer qualify. Pigs have split hooves but do not chew their cud, so pork is forbidden. Permitted fowl (chicken, turkey, duck, and others) are also fleishig. Kosher meat must be slaughtered by a trained shochet through a process called shechita, then inspected and salted to draw out the blood. You cannot mix fleishig food with dairy on the same plate, in the same pot, or in the same meal. Most communities wait between meat meals and dairy meals. The waiting period ranges from one hour to six hours, depending on the tradition you follow.
Dairy (milchig). Milk, cheese, butter, yogurt, and other dairy products from kosher animals are milchig. Most Jewish families keep separate dishes, utensils, and sponges for dairy to prevent any crossover with meat. You cannot cook dairy with meat, use the same pots for both, or eat them together at the same meal. Hard cheeses and some other dairy products require kosher certification because of the rennet and processing involved.
Pareve. Everything that is neither meat nor dairy is pareve. Fish, eggs, fruits, vegetables, and grains are all pareve. Pareve food can be eaten alongside either meat or dairy, which is one reason fish is so practical in a kosher kitchen. A salmon fillet works at a dairy dinner or a meat dinner without any conflict.
One nuance worth knowing: many Ashkenazic communities follow the custom (minhag) not to eat fish and meat on the same plate. This is not a Torah prohibition, but it is widely observed. You can eat fish and then meat at the same meal, just not combined on one dish. The OU and Star-K both note this custom, and your community’s rabbi can tell you the local practice.
How to Keep Kosher With Fish: The Fins-and-Scales Rule
Leviticus 11:9-12 and Deuteronomy 14:9-10 give a precise rule for fish: it must have fins and scales. The scales must be the kind that lift off without tearing the skin. Halachically, those are cycloid or ctenoid scales. Fish with embedded scales that don’t detach, like sturgeon’s ganoid scales, or sharks’ placoid denticles (which aren’t true scales at all), are not kosher, even though you might call them “scaled” in a biology context.
In practical terms, salmon, tuna, cod, tilapia, halibut, flounder, mahi-mahi, trout, and mackerel are all kosher. Catfish, shark, eel, and sturgeon are not. All shellfish are not kosher: shrimp, crab, lobster, clams, oysters, scallops, and squid all lack the fins-and-scales test. The Orthodox Union (OU) and the Chicago Rabbinical Council (cRc) both publish detailed kosher fish lists that apply this standard across hundreds of species. The full kosher fish list on this site covers 291 species.
The good news for fish is that fresh, whole fish with skin and scales intact is easy to verify yourself. You can see the fins, feel the removable scales, and confirm the species. That’s why most kosher authorities say fresh whole fish doesn’t need a hechsher, you can assess it directly. Filleted, smoked, or canned fish loses those visual cues, and certification from a recognized agency matters more.
How Kosher Certification Works
A hechsher is a kosher certification mark from a recognized agency. When you see one on a food package, it means a mashgiach (kosher supervisor) from that agency has verified that the product and its production process meet kosher standards.
The five major certification agencies in the United States are the Orthodox Union (OU), the Chicago Rabbinical Council (cRc), Star-K, OK Kosher, and Kof-K. The OU’s circle-U symbol is the most widely recognized worldwide. All five are accepted by observant communities, and products certified by any of them are considered reliably kosher.
A plain letter “K” with no agency symbol behind it is a self-declared mark. No third party has verified it. It tells you almost nothing about the product’s actual kosher status. When you’re shopping, look for one of the recognized agency symbols, not a standalone K.
For fish specifically, fresh fillets and packaged fish products should carry a hechsher from one of these agencies. Canned tuna, smoked salmon, and frozen fish fillets all benefit from certification because you can’t verify the species or the processing equipment by looking at them. You can find more detail on this in the guide on when fish needs a hechsher.
Shopping for Kosher Food: A Practical Guide
For Jewish families starting out, the grocery store is where keeping kosher becomes practical. The steps are the same everywhere: find the kosher certification mark, read the ingredients, and separate meat and dairy purchases into your shopping cart and your bags.
Most major supermarkets in America now carry a kosher section with certified products. Natural food stores and Jewish community grocery stores tend to carry a wider range. During Jewish holidays like Passover and Rosh Hashanah, even mainstream stores often expand their kosher offerings significantly. Many families do a big kosher shop before Shabbat, stocking up on fish, dairy, and pareve foods that work across both meat and dairy meals during the week.
When you’re shopping for meat, look for the kosher certification and the cut. Kosher beef and poultry comes from animals slaughtered by a shochet, inspected for certain organ or lung defects (a process called bedika), and then salted to draw out blood. The label will say which certifying agency approved it. Certain cuts from the hindquarters of cattle require a more involved process (nikur, removing the sciatic nerve and specific fats) and are often unavailable in America, so most American kosher meat comes from the forequarters.
For fish, the shopping rules are simpler. Whole fresh fish with skin and scales is easy to verify yourself. Fillets and processed fish need a hechsher. The KosherFish lookup tool covers 291 species and can help you check any fish at the fish counter before you purchase it.
Packaged products require reading the label. Look for the certification mark and check whether the product is labeled meat, dairy, or pareve. If you’re serving it at a meat meal, pareve is fine. If it’s labeled dairy, keep it off the meat dishes and away from meat cooking equipment. Build a reference list of brands your family trusts for each category, and shopping gets much faster over time.
Setting Up a Kosher Kitchen: The Basics
Keeping kosher at home means two separate sets of items: one for meat and one for dairy. Separate dishes, pots, pans, utensils, cutting boards, and sponges. Meat foods and dairy foods cannot touch the same equipment without going through a kashering process. In practice, this means you need two complete sets of dishes and cooking equipment, one labeled or color-coded for meat and one for dairy.
If you’re starting fresh, buying new items is the simplest path. For a kitchen that’s already been used for non-kosher cooking, you’ll need to kasher the equipment that can be kashered before it’s kosher to use. The kashering process varies by material and prior use, and the rules come from rabbinic tradition applied to the laws in the Torah.
The general principle of kashering: items absorb the “taste” of food cooked in them, and that taste can be released through the same type of heat. Pots and utensils used on a stovetop are kashered by boiling. Items used with cold foods are kashered by soaking in cold water. An oven is kashered by running it at high heat after thorough cleaning. A separate broiler pan for meat and for dairy is recommended. Sinks can often be kashered by pouring boiling water over them after a thorough cleaning. Some prefer to keep separate dish racks, too. Items made of glass present their own rules, and certain materials, like earthenware, generally cannot be kashered at all.
Here are the steps for a kitchen conversion: clean all dishes, pots, and surfaces thoroughly, wait 24 hours after the last non-kosher use, then kasher the items that can be kashered in sequence, starting with utensils, pots, and dishes that touch fire, then the oven, then counters and sinks. Before you start, buy your new kosher meat, dairy, and pantry products, replace old oven racks if necessary, and set up your labeling system. After kashering, your kitchen is set up for keeping kosher going forward.
Some items in your pantry may need to be replaced rather than kashered. Certain cooking sprays, baking powders, and processed foods may not be kosher even if they seem simple. When in doubt, buy certified kosher replacements. Building a kosher pantry step by step, replacing items as you use them up, is one practical way to make the transition without throwing everything out at once.
Consult a rabbi and use reliable kashrut resources like the OU at oukosher.org before you start the kashering process. Both are valuable. The rules can depend on your community’s practice, the specific materials in your kitchen, and whether the equipment was used with meat or dairy. The steps involved depend on your kitchen’s materials and history, and what counts as properly kashered depends on getting those details right. This site covers Jewish dietary law as it applies to fish specifically. For the full kitchen setup, a rabbinic authority is the right guide. The OU and Star-K both offer free online resources with step-by-step kashering guides.
Common Questions When You Start Keeping Kosher
Do I need to kasher my kitchen? If you’re starting from scratch with a kitchen that’s been used for non-kosher food, yes. Koshering involves cleaning and sometimes applying heat to utensils, counters, ovens, and stovetops according to specific procedures that vary by material and prior use. A rabbi who specializes in kashrut can walk you through it. The OU’s oukosher.org has practical step-by-step guides as well.
Can I eat at a non-kosher restaurant? Generally, no, if you observe kosher fully. Non-kosher restaurants use shared equipment and may have non-kosher ingredients mixed into what looks like a simple dish. Most Orthodox authorities recommend certified kosher establishments. The question of whether plain grilled fish at a non-kosher restaurant is acceptable is addressed differently by different poskim. Check your community’s standard.
Is kosher food more expensive? For certified meat and processed products, often yes. Fresh produce is comparable to any other grocery. Fresh, whole fish from a reputable fishmonger is often the same price as anywhere else, and you can verify it yourself if it still has skin and scales.
What’s the easiest place to start? Fish. You don’t need to wait on anything or kasher a new pot. Just check the species with the KosherFish tool, and you’re done. It’s pareve, the rule is clear, and fresh whole fish is easy to assess. The KosherFish lookup tool answers the species question instantly for any fish you’re unsure about.
Kosher Food Categories: A Quick Reference
| Food | Category | Kosher? | Notes |
|---|---|---|---|
| Beef, lamb, goat | Meat (fleishig) | ✅ Yes | Requires shechita and salting. No mixing with dairy |
| Pork | Meat | ❌ No | Does not chew its cud, forbidden by Leviticus 11 |
| Chicken, turkey, duck | Meat (fleishig) | ✅ Yes | Requires kosher slaughter. Treated as meat for separation rules |
| Milk, cheese, butter | Dairy (milchig) | ✅ Yes | Cannot be mixed with meat. Hard cheeses need certification |
| Fish with fins and removable scales | Pareve | ✅ Yes | Whole fresh fish: no hechsher needed. Processed: get certification |
| Shellfish, eel, shark, catfish | Pareve definition only | ❌ No | Fail the fins-and-scales test, forbidden by Torah |
| Eggs | Pareve | ✅ Yes | Check for blood spots, which render an egg non-kosher |
| Fruits, vegetables, grains | Pareve | ✅ Yes | Check produce for insects, especially leafy greens |
| Meat and dairy together | Forbidden combination | ❌ No | Applies to cooking, serving, and utensils |
Check Any Fish with KosherFish
Fish is the one kosher category you can often verify at the counter, if the fish still has its skin and scales. But memorizing the kosher status of 291 different species is a lot to ask. That’s exactly where KosherFish can help.
The lookup tool on the homepage gives you an instant kosher verdict for any fish you type in. The full kosher fish list lets you browse all 291 species in one place. The iOS app and Android app put both in your pocket for the fish market, the sushi counter, or the restaurant menu. You shouldn’t have to guess. Now you don’t have to.
Frequently Asked Questions About How to Keep Kosher
How do I start keeping kosher?
Start with what you eat at home. Replace non-kosher meat with shechita-slaughtered, certified meat, remove forbidden foods from your kitchen, and learn the rules for separating meat and dairy. Fish is a natural starting point because it’s pareve, the rule is clear (fins and removable scales), and fresh whole fish is easy to verify yourself. Talk to a rabbi for guidance on koshering your kitchen and which community standards to follow.
What foods are always forbidden under kosher law?
Pork and all pork products, shellfish (shrimp, crab, lobster, clams, oysters, scallops), squid, octopus, eel, shark, catfish, and sturgeon are always forbidden. Mixing meat and dairy is also prohibited, as is consuming blood. These prohibitions come from Leviticus 11 and Deuteronomy 14 and apply without exception in halachic tradition.
Is all fish kosher?
No. Only fish with fins and scales that can be removed without tearing the skin are kosher under Jewish law (Leviticus 11:9-12). Salmon, tuna, cod, and tilapia are kosher. Catfish (no scales), shark (placoid denticles, not true removable scales), and sturgeon (embedded ganoid scales) are not. The OU and cRc both publish kosher fish lists. You can look up any species on the KosherFish list.
What does pareve mean in kosher?
Pareve means neither meat nor dairy. Fish, eggs, fruits, vegetables, and grains are all pareve. You can eat pareve food with either meat or dairy without violating the meat-dairy separation. Fish is pareve. The minhag in many Ashkenazic communities is to avoid eating fish and meat on the same plate, but this is a custom, not a Torah prohibition. Fish and dairy together is generally permitted.
Do I need a kosher symbol on fresh fish?
For fresh, whole fish with skin and scales still attached, most kosher authorities say a hechsher is not required. You can see the fins and the removable scales yourself. Once fish is filleted, smoked, canned, or otherwise processed, the identifying marks are gone, and a hechsher from the OU, cRc, Star-K, OK, or Kof-K matters. See the guide on when fish needs a hechsher for details.
Can I eat fish at a non-kosher restaurant?
It depends on your community’s standard. Some people will eat plain grilled fish at a non-kosher restaurant if the species is clearly kosher and served simply. Most Orthodox poskim recommend eating only at certified kosher establishments, because shared equipment and unverified ingredients are hard to rule out. Ask your rabbi what your community follows.
How do I recognize a reliable kosher certification on packaged food?
Look for the symbol of a recognized agency: the OU (a U inside a circle), cRc, Star-K, OK Kosher, or Kof-K. These agencies certify production facilities and verify ingredients. A plain letter “K” with no agency name or logo is self-declared. It tells you the company believes its product is kosher, but no third party has verified it. For fish, the OU and cRc also maintain public kosher fish lists you can reference.
The Bottom Line
Keeping kosher means following a clear set of Torah rules: which animals are permitted, how they must be prepared, and how to keep meat and dairy separate. Fish is pareve and one of the easiest categories to navigate. Fresh whole fish with visible fins and removable scales is kosher and easy to verify. Processed fish needs a hechsher from a recognized agency like the OU or cRc.
For those learning how to keep kosher, fish is the best starting point. The KosherFish lookup tool gives you an instant answer. The full kosher fish list covers 291 species. The iOS app and Android app put both in your pocket at the market or the restaurant. For the broader kashrut questions, the OU at oukosher.org has comprehensive practical resources, step-by-step guides, and a list of certified products, and your own rabbi is the right authority for your community’s specific standards.
More on this site: What Makes a Fish Kosher, Is Fish Pareve, Does Fish Need a Hechsher, Kosher Dietary Laws Explained, Kosher Symbols Explained.