Soy sauce is not a monolith—it has many iterations and each has its specific usage in cuisines around the world. In many stir-fry recipes, you may stumble upon an instruction calling for “light soy sauce.”
So, what exactly is light soy sauce and how does it differ from, say, “regular” soy sauce that you’d pick up from a grocery store? Does it?
The short answer is that it depends on the cuisine. There are multiple descriptors of soy sauce (dark, thick, thin, light), but they’re uniquely used within each cuisine to differentiate one variety from another. A “dark” Japanese soy sauce may vary greatly in texture and color from a “dark” Filipino soy sauce. You can read all about that and more in our recent soy sauce review.
Bottom line? Look at the intended use before buying and don’t solely use the terms “dark,” “light,” thick,” or “thin” as guiding principles for what a soy sauce will be like across cuisines.
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What Is Light Soy Sauce?
Generally speaking, light soy sauce is a flavoring agent that adds nuanced umaminess to the dish. It’s made from fermented soybeans and has a thin, slightly watery texture. It is typically what you’ll find in most grocery stores and is often what a Chinese recipe is calling for when it just says “soy sauce” in the ingredient list.
Chinese light soy sauce (sheng chou) is the quintessential ingredient in Chinese and Taiwanese cooking. Its name translates to “fresh extraction,” but it’s known as “light” soy sauce. Reddish-brown in color, it often has a “floral” and “port-like” aroma.
A subcategory of light soy sauce is “first press,” meaning the first batch of liquid pressed from the soybean mash after it has fermented for six months. It had more “robust soybean flavors” and was “sharper” than the ones brewed for longer. This is a versatile all-purpose soy sauce, great for recipes that call for soy sauce without specifying a certain type, such as stir-fries, stews, or braises. It’s also good in cold dishes, such as chilled tofu and smashed cucumber salad.
But don’t be fooled by the labeling. For example, the all-purpose Japanese koikuchi shoyu is described as “dark” in color relative to the other regularly used Japanese variety usukuchi, but its usage is more similar to Chinese light soy sauce, an everyday type.
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What Are Some Other Types of Light Soy Sauce?
Usukuchi shoyu, also known as Japanese light soy sauce, is amber-hued and thin and is the preferred sauce in the Kansai region of Japan. It’s used for seasoning food rather than coloring it. It’s saltier than koikuchi shoyu with less funk. Usukuchi is used in Kansai cuisine, where popular dishes include takoyaki (battered and grilled octopus balls), okonomiyaki (Osaka-style savory pancakes), and yakiniku (grilled meat).
You can use usukuchi in Japanese dishes when your goal is to add a bit of seasoning while preserving the dish’s own flavor, color, and aroma, such as in dashi and dipping sauce.
What Is Dark Soy Sauce?
Dark soy sauce is often thicker and more viscous than light soy sauce, and it can add more coloring to dishes.
It is typically added toward the end of cooking in red-braised pork belly and other “red-braised” proteins. This is a technique called “shang se,” employed because the soy sauce can overly darken the food if cooked too long. Because it’s so viscous and dark, most dishes only need a teaspoon (or less).
Lao chou (Chinese dark soy sauce) translates to “old extraction,” as the liquid comes from soybeans that have been fermented longer than those used to make light soy sauce. Sugar is sometimes used to give it a viscous texture and dark coloring, says Taylor Holliday, proprietor of Sichuan specialty shop The Mala Market.
It’s also a bit sweet, roasty, and winelike. In addition to traditional dark soy sauce, you can find a flavored variety infused with straw mushrooms or shiitake mushrooms—the mushrooms add umami and richness. Both styles of soy sauce are dark brown and more viscous in texture, but less salty, than Chinese light soy sauce.
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What Are Some Other Types of Dark Soy Sauce?
Koikuchi shoyu—which can be translated as “dark,” “heavy,” “dark-colored,” or “thick” soy sauce—accounts for about 80 percent of the Japanese market. If you pick up a bottle of Japanese soy sauce from the grocery store, it’s probably a koikuchi shoyu. It’s dark brown and a bit sweeter than usukuchi (Japanese light soy sauce), thanks to the addition of wheat.
Koikuchi is the Japanese everyday soy sauce, good for most applications, such as stir-fries, marinades, and braising.
Is Light Soy Sauce the Same As “Low-Sodium” Soy Sauce?
No. When you come across a soy sauce labeled as “light,” it most likely means it’s a sheng chou, the all-purpose soy sauce. Ironically, it’s saltier than its dark counterpart, lao chou, a more aged, viscous version of the light soy sauce that’s used for braising and adding color to a dish.
As with all soy sauce shopping, it depends on how you’re planning on using the ingredient and the cuisine which it’s from. In Japanese cuisine, usukuchi shoyu also has a higher sodium content than Japanese dark soy sauce.
Low-sodium soy sauce is made the same way as traditional soy sauces but has its sodium level reduced, making it less salty.