# Infer types

> This document is the Markdown version of [valibot.dev/guides/infer-types/](https://valibot.dev/guides/infer-types/). For the complete documentation index, see [llms.txt](https://valibot.dev/llms.txt).

Another cool feature of schemas is the ability to infer input and output types. This makes your work even easier because you don't have to write the type definition yourself.

## Infer input types

The input type of a schema corresponds to the TypeScript type that the incoming data of a schema must match to be valid. To extract this type you use the utility type [`InferInput`](/api/InferInput.md).

> You are probably interested in the input type only in special cases. In most cases, the output type should be sufficient.

```ts
import * as v from 'valibot';

const LoginSchema = v.object({
  email: v.string(),
  password: v.string(),
});

type LoginInput = v.InferInput<typeof LoginSchema>; // { email: string; password: string }
```

## Infer output types

The output type differs from the input type only if you use [`optional`](/api/optional.md), [`nullable`](/api/nullable.md), [`nullish`](/api/nullish.md) or [`undefinedable`](/api/undefinedable.md) with a default value or [`brand`](/api/brand.md), [`readonly`](/api/readonly.md) or [`transform`](/api/transform.md) to transform the input or data type of a schema after validation. The output type corresponds to the output of [`parse`](/api/parse.md) and [`safeParse`](/api/safeParse.md). To infer it, you use the utility type [`InferOutput`](/api/InferOutput.md).

```ts
import * as v from 'valibot';
import { hashPassword } from '~/utils';

const LoginSchema = v.pipe(
  v.object({
    email: v.string(),
    password: v.pipe(v.string(), v.transform(hashPassword)),
  }),
  v.transform((input) => {
    return {
      ...input,
      timestamp: new Date().toISOString(),
    };
  })
);

type LoginOutput = v.InferOutput<typeof LoginSchema>; // { email: string; password: string; timestamp: string }
```

## Infer issue types

You can also infer the possible issues of a schema. This can be useful if you want to handle the issues in a particular way. To extract this information from a schema you use the utility type [`InferIssue`](/api/InferIssue.md).

```ts
import * as v from 'valibot';

const LoginSchema = v.object({
  email: v.pipe(v.string(), v.email()),
  password: v.pipe(v.string(), v.minLength(8)),
});

type Issue = v.InferIssue<typeof LoginSchema>; // v.ObjectIssue | v.StringIssue | v.EmailIssue<string> | v.MinLengthIssue<string, 8>
```