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# Error Handling

## Overview

Fallible Viem functions expose an `ErrorType` from the same namespace as their options and return
type. Concrete error classes let applications narrow those declared failures at runtime without
parsing messages.

Every Viem error inherits from [`Errors.BaseError`](/docs/errors/base-error) and preserves its
underlying failure as `cause`.

```ts twoslash
import { Actions, ContractError } from 'viem'

function getMessage(error: Actions.contract.read.ErrorType) {
  if (error instanceof ContractError.ContractFunctionExecutionError)
    return `Could not read ${error.functionName}.`
  if (error instanceof Error) return error.message
  return 'Unknown error.'
}
```

<Cards>
  <Card title="Typed Errors" description="Use function ErrorType namespaces and narrow runtime failures." icon="lucide:braces" to="/docs/errors/typed-errors" />

  <Card title="Contract Errors" description="Handle contract failures and decoded revert reasons." icon="lucide:file-warning" to="/docs/errors/contract" />

  <Card title="RPC Errors" description="Match node failures across reverts, fees, nonces, and gas." icon="lucide:server-crash" to="/docs/errors/rpc" />

  <Card title="Base Error" description="The base error class inherited by all errors thrown by Viem." icon="lucide:circle-alert" to="/docs/errors/base-error" />

  <Card title="Configuration" description="Set Viem-scoped defaults (docs origin, version) applied to every error." icon="lucide:settings" to="/docs/errors/configuration" />
</Cards>