Errors

By default (throwOnError: true) failed HTTP calls throw a FetchError.

import { createFetch, isFetchError } from 'tanstack-fetch'

const api = createFetch({ baseUrl: 'https://api.example.com' })

try {
  await api.get('/missing')
} catch (error) {
  if (isFetchError(error)) {
    console.log(error.status) // 404
    console.log(error.code) // e.g. from body
    console.log(error.message)
    console.log(error.body)
  }
}

With TanStack Query

const { error } = useQuery({
  queryKey: ['users'],
  queryFn: ({ signal }) => api.get('/users', { signal }),
})

if (isFetchError(error) && error.status === 404) {
  return <p>Not found</p>
}

Opt into FetchResult

const result = await api.get<User>('/users/1', { throwOnError: false })
if (!result.ok) {
  console.log(result.error)
} else {
  console.log(result.data)
}

Helpers

Helper	Purpose
isFetchError(error)	Narrow to FetchError
isAbortError(error)	Abort / timeout — usually not an HTTP failure
createFetchError(result)	Build a FetchError from a failed result