Zod
TypeScript-first schema validation with static type inference
by @colinhacks
Featured sponsor: Jazz
### [Read the docs →](https://zod.dev/api)
## What is Zod?
Zod is a TypeScript-first validation library. Define a schema and parse some data with it. You'll get back a strongly typed, validated result.
```ts
import * as z from "zod";
const User = z.object({
name: z.string(),
});
// some untrusted data...
const input = {
/* stuff */
};
// the parsed result is validated and type safe!
const data = User.parse(input);
// so you can use it with confidence :)
console.log(data.name);
```
## Features
- Zero external dependencies
- Works in Node.js and all modern browsers
- Tiny: `2kb` core bundle (gzipped)
- Immutable API: methods return a new instance
- Concise interface
- Works with TypeScript and plain JS
- Built-in JSON Schema conversion
- Extensive ecosystem
## Installation
```sh
npm install zod
```
## Basic usage
Before you can do anything else, you need to define a schema. For the purposes of this guide, we'll use a simple object schema.
```ts
import * as z from "zod";
const Player = z.object({
username: z.string(),
xp: z.number(),
});
```
### Parsing data
Given any Zod schema, use `.parse` to validate an input. If it's valid, Zod returns a strongly-typed _deep clone_ of the input.
```ts
Player.parse({ username: "billie", xp: 100 });
// => returns { username: "billie", xp: 100 }
```
**Note** — If your schema uses certain asynchronous APIs like `async` [refinements](#refine) or [transforms](#transform), you'll need to use the `.parseAsync()` method instead.
```ts
const schema = z.string().refine(async (val) => val.length <= 8);
await schema.parseAsync("hello");
// => "hello"
```
### Handling errors
When validation fails, the `.parse()` method will throw a `ZodError` instance with granular information about the validation issues.
```ts
try {
Player.parse({ username: 42, xp: "100" });
} catch (err) {
if (err instanceof z.ZodError) {
err.issues;
/* [
{
expected: 'string',
code: 'invalid_type',
path: [ 'username' ],
message: 'Invalid input: expected string'
},
{
expected: 'number',
code: 'invalid_type',
path: [ 'xp' ],
message: 'Invalid input: expected number'
}
] */
}
}
```
To avoid a `try/catch` block, you can use the `.safeParse()` method to get back a plain result object containing either the successfully parsed data or a `ZodError`. The result type is a [discriminated union](https://www.typescriptlang.org/docs/handbook/2/narrowing.html#discriminated-unions), so you can handle both cases conveniently.
```ts
const result = Player.safeParse({ username: 42, xp: "100" });
if (!result.success) {
result.error; // ZodError instance
} else {
result.data; // { username: string; xp: number }
}
```
**Note** — If your schema uses certain asynchronous APIs like `async` [refinements](#refine) or [transforms](#transform), you'll need to use the `.safeParseAsync()` method instead.
```ts
const schema = z.string().refine(async (val) => val.length <= 8);
await schema.safeParseAsync("hello");
// => { success: true; data: "hello" }
```
### Inferring types
Zod infers a static type from your schema definitions. You can extract this type with the `z.infer<>` utility and use it however you like.
```ts
const Player = z.object({
username: z.string(),
xp: z.number(),
});
// extract the inferred type
type Player = z.infer;
// use it in your code
const player: Player = { username: "billie", xp: 100 };
```
In some cases, the input & output types of a schema can diverge. For instance, the `.transform()` API can convert the input from one type to another. In these cases, you can extract the input and output types independently:
```ts
const mySchema = z.string().transform((val) => val.length);
type MySchemaIn = z.input;
// => string
type MySchemaOut = z.output; // equivalent to z.infer
// number
```
