Recipes

t3-env supports the full power of Zod meaning you can use transforms, default values etc. to create a set of powerful and flexible validation schemas for your environment variables. Below we'll look at a few example recipes for

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All environment variables are strings, so make sure that the first ZodType is a z.string(). This will be enforced on type-level in the future.

Booleans

Coercing booleans from strings is a common use case. Below are 2 examples of how to do this, but you can choose any coercian logic you want.

export const env = createEnv({
  server: {
    COERCED_BOOLEAN: z
      .string()
      // transform to boolean using preferred coercion logic
      .transform((s) => s !== "false" && s !== "0"),
 
    ONLY_BOOLEAN: z
      .string()
      // only allow "true" or "false"
      .refine((s) => s === "true" || s === "false")
      // transform to boolean
      .transform((s) => s === "true"),
  },
  // ...
});

export const env = createEnv({
  server: {
    COERCED_BOOLEAN: z
      .string()
      // transform to boolean using preferred coercion logic
      .transform((s) => s !== "false" && s !== "0"),
 
    ONLY_BOOLEAN: z
      .string()
      // only allow "true" or "false"
      .refine((s) => s === "true" || s === "false")
      // transform to boolean
      .transform((s) => s === "true"),
  },
  // ...
});

Numbers

Coercing numbers from strings is another common use case.

export const env = createEnv({
  server: {
    SOME_NUMBER: z
      .string()
      // transform to number
      .transform((s) => parseInt(s, 10))
      // make sure transform worked
      .pipe(z.number()),
  },
  // ...
});

export const env = createEnv({
  server: {
    SOME_NUMBER: z
      .string()
      // transform to number
      .transform((s) => parseInt(s, 10))
      // make sure transform worked
      .pipe(z.number()),
  },
  // ...
});