Somewhere you are utilizing the next/link component, Router#push, or Router#replace with a relative route in your href that has an external as value. The as value must be relative also or only href should be used with an external URL.

Note: this error will only show when the next/link component is clicked not when only rendered.

Incompatible href and as

import Link from 'next/link'

export default function Page(props) {
  return (
    <>
      <Link href="/invalid" as="mailto:john@example.com">
        <a>Invalid link</a>
      </Link>
    </>
  )
}

Compatible href and as

import Link from 'next/link'

export default function Page(props) {
  return (
    <>
      <Link href="mailto:john@example.com">
        <a>Invalid link</a>
      </Link>
    </>
  )
}

Look for any usage of the next/link component, Router#push, or Router#replace and make sure that the provided href and as values are compatible

• Routing section in Documentation