If your app handles tags, categories, or multi-select fields, you’re likely validating string arrays. Zod makes it easy to define schemas that enforce exactly what your input should look like.

To define a Zod schema that validates an array where every item must be a string, use the following:

const schema = z.array(z.string());

This ensures that every item in the array is a string — no numbers, booleans, or nulls. Whether you’re handling tags, interests, roles, or checkbox options, this pattern is your starting point.

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How to Validate Lists of Strings with Zod

You can validate user input that is expected to be an array of strings using Zod’s built-in schema methods. This is particularly useful when working with dynamic form fields, multi-select dropdowns, or query parameters where the input is a list of strings.

const inputSchema = z.array(z.string());

inputSchema.parse(['tecktol', 'founder', 'sharukhan']); // Valid
inputSchema.parse(['tecktol', 123]);  // Invalid number found

In this example, the Zod schema strictly validates that every element in the array must be a string. If any value — like a number, boolean, or null — appears, the validation will fail. This pattern is foundational when validating things like user-defined tags, categories, selected roles, or checkbox group values.

Adding Constraints to String Arrays

Need more control over the input structure? Zod allows you to define constraints not only on the array itself, but also on each individual string inside it.

const schema = z.array(z.string().min(2).max(10)).min(1).max(5);

This enhanced schema applies layered validation rules:

• Each string must be between 2 and 10 characters
• The entire array must contain at least 1 and no more than 5 items

Such a setup is ideal for validating user-submitted lists like interests, tags, roles, or even feature flags — where both the content and quantity of items matter. You ensure the array isn’t too large, and that each string is meaningful (e.g., not empty or overly long).

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Real-World Example: Validating Form Tags with a Zod Array of Strings

In real-world applications, especially in content management systems or user-generated platforms, it’s common to allow users to submit multiple tags through a form. These tags are typically represented as a list of strings, which must be validated to prevent issues like blank values or invalid characters.

Let’s say you’re building a blog post form where users can add tags such as "react", "typescript", or "zod".

Here’s how you can define a Zod schema to validate an array of strings representing these tags:

const tagSchema = z.array(z.string().min(1));

tagSchema.parse(['react', 'typescript', 'zod']); // Valid

In this example, z.string().min(1) ensures that each tag is a non-empty string, and z.array(...) wraps the string validation to enforce that the input is an array. So you’re validating both the structure of the input (it must be an array) and the content of each item (each must be a non-empty string).

This is critical in form validation because users may:

• Accidentally submit empty values (e.g., hitting enter without typing)
• Include invalid types (e.g., numbers, booleans)
• Send poorly formatted data through APIs or frontends

By using z.array(z.string().min(1)), you avoid all of those risks with a type-safe, scalable solution. This pattern can be reused across form fields like:

• Tags and categories
• Roles and permissions
• Filter selections (checkbox groups, multi-select dropdowns)
• Keyword lists and dynamic labels

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Restricting Strings to Specific Values Using Enum Support

When you want to restrict each string in an array to a known set of options—like article statuses or roles—combine z.array() with z.enum(). This approach strictly validates each item in the array against the enum values.

For a complete guide on defining and working with enums, check our full Zod enum guide.

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Creating Enum-Based String Arrays from Constants in Zod

const categories = ['dev', 'design', 'marketing'] as const;
const categoryEnum = z.enum(categories);

When validating arrays of strings, and you already have a list of allowed values (e.g., categories, tags), Zod lets you dynamically convert that list into an enum. This ensures every string in the array strictly matches one of your predefined options.

By casting your array to a string literal type using as const, and passing it to z.enum, you create a reusable schema for consistent validation across your forms or APIs. This approach avoids manual repetition and works well in projects that share constants between frontend and backend.

This pattern is especially helpful when:

• You need to validate an array of categories or tags against a constant list
• You’re aiming to reuse string arrays from shared config files or enums
• You want strict type safety with minimal duplication

Want to learn more about working with Zod enums in different contexts? Explore this complete guide on z.enum usage.

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Handling Both Single and Multiple Strings

In many API designs or form submissions, it’s common to accept either a single string or an array of strings. For example, URL query parameters might look like this:

?tags=react
?tags=react&tags=node

Here, the value of tags can be a single string ("react") or a list of strings (["react", "node"]). This situation often arises in filters, category selectors, or search parameters in REST APIs or Next.js route handlers.

To handle this dual-input format in Zod, you can create a schema that accepts both:

In the below schema, we use z.union() to define a validation rule that accepts either a single string or an array of strings:

const flexibleSchema = z.union([z.string(), z.array(z.string())]);

flexibleSchema.parse('react');            // ✅
flexibleSchema.parse(['react', 'node']);  // ✅

In the above schema:

• z.string() accepts a single tag like "react"
• z.array(z.string()) allows a full list like ["react", "node", "zod"]

By combining both with z.union(), you cover both use cases without writing separate handlers — improving validation accuracy, developer experience, and code maintainability.

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Converting a Comma-Separated String into an Array of Strings

In some scenarios, especially when dealing with form submissions or query parameters, the input may arrive as a comma-separated string instead of an actual array. For example:

?skills=html,css,javascript

In this case, the input is technically a single string ("html,css,javascript"), but the expected format is a Zod-valid array of strings. This pattern is common in filters, CSV-style input fields, or APIs that serialize list data into strings.

const csvSchema = z
  .string()
  .transform((value) => value.split(',').map((s) => s.trim()));

csvSchema.parse('a,b,c'); // ['a', 'b', 'c']

In the below schema, we enhance the previous transformation by chaining .pipe() to apply further validation on the resulting array:

const validCsvArray = csvSchema.pipe(z.array(z.string().min(1)));

This is especially useful when handling:

• CSV uploads with optional columns
• Comma-delimited form fields that users might accidentally leave blank
• URL query parameters passed as a string but expected as a Zod-validated array of non-empty strings

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Working with Object Schemas that Contain Arrays of Strings

In real-world applications, it’s common to structure your data as objects containing multiple fields — and sometimes those fields include an array of strings. This pattern often appears in user profiles, form submissions, or API payloads.

For example, you might receive an object like this:

const userSchema = z.object({
  username: z.string(),
  tags: z.array(z.string()),
});

userSchema.parse({
  username: 'sharukhan',
  tags: ['founder', 'creator'],
}); // ✅

This approach is ideal when you’re working with:

• Form data submitted by users (e.g., selected tags or interests)
• Nested objects in JSON APIs where a key holds a list of labels, roles, or filters
• Profile schemas with dynamic or optional string arrays

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Literal String Matching in Zod Arrays

In the below schema, we define an array of strings where only 'yes', 'no', or 'maybe' are accepted:

const literalSchema = z.array(
  z.union([
    z.literal('yes'),
    z.literal('no'),
    z.literal('maybe'),
  ])
);

literalSchema.parse(['yes', 'no']);   // ✅
literalSchema.parse(['sure']);        // ❌ not allowed

This technique is ideal when:

• You need tight control over accepted values
• The list of valid strings is very short and unlikely to change
• You want to avoid creating a separate enum when it’s unnecessary

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Summary Table

Use Case	Schema
Simple list of strings	z.array(z.string())
Length constraints	.min(x).max(y) on strings/arrays
Allowed values only	z.enum([...]) inside array
Allow single string or list	z.union([z.string(), z.array(z.string())])
From comma-separated string	z.string().transform(...).pipe(...)
Unique items only	.refine(...Set logic...)
Exact string matches	z.literal('...') inside array

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Wrap-Up

Zod makes working with arrays of strings effortless — from basic validations to strict matching and dynamic transformations. Whether you’re validating form data, query strings, or JSON payloads, these techniques cover every real-world use case.

If you’re just starting, begin with z.array(z.string()) and layer in more constraints as your app grows. It keeps your codebase type-safe, clean, and robust.