psf/requests · error · MissingSchema

Invalid URL : No scheme supplied. Perhaps you meant…

Error message

Invalid URL {url!r}: No scheme supplied. Perhaps you meant https://{url}?

What it means

Raised by PreparedRequest.prepare_url when parse_url succeeded but returned an empty scheme. Every HTTP(S) request needs a scheme to route through the correct adapter; a URL like 'example.com/path' parses but has no scheme, so requests raises MissingSchema and suggests the most likely fix (prepending 'https://'). This catches the common 'forgot the protocol' mistake.

Solutions

1. Prefix the URL with a scheme: requests.get('https://' + url) if you know it should be HTTPS, or normalize inputs upstream.
2. Validate with urllib.parse.urlparse and require a non-empty .scheme before issuing the request.
3. For 'localhost'-style shortcuts, use the full form 'http://localhost:8000'.

Example fix

// before
requests.get('example.com/api')

// after
requests.get('https://example.com/api')

from urllib.parse import urlparse

def ensure_scheme(url: str, default: str = 'https') -> str:
    if '://' not in url:
        url = f'{default}://{url}'
    return url

from urllib.parse import urlparse

def has_scheme(url: str) -> bool:
    return bool(urlparse(url).scheme)

from requests.exceptions import MissingSchema

try:
    resp = requests.get(url)
except MissingSchema:
    resp = requests.get('https://' + url)

When it happens

Trigger: Calling requests.get('example.com/api') (no scheme); building URLs by concatenating a host without a protocol prefix; receiving a bare hostname from config and passing it straight to requests.

Common situations: User-supplied 'domains' instead of full URLs; configs that store hosts separately from schemes; copy-pasting a URL that lost its 'https://' when the browser stripped it.

Related errors

• {e.args}
• Invalid URL : No host supplied
• {e}
• Auth hooks must be callable.
• Cookie headers should be added with…

AI-assisted analysis of psf/requests@8068356288 (2026-08-11). Data as JSON: /api/errors/11675c841b2d515d. Report an issue: GitHub.

Appendix: source

Thrown at src/requests/models.py:516

        # Remove leading whitespaces from url
        url = url.lstrip()

        # Don't do any URL preparation for non-HTTP schemes like `mailto`,
        # `data` etc to work around exceptions from `url_parse`, which
        # handles RFC 3986 only.
        if ":" in url and not url.lower().startswith("http"):
            self.url = url
            return

        # Support for unicode domain names and paths.
        try:
            scheme, auth, host, port, path, query, fragment = parse_url(url)
        except LocationParseError as e:
            raise InvalidURL(*e.args)

        if not scheme:
            raise MissingSchema(
                f"Invalid URL {url!r}: No scheme supplied. "
                f"Perhaps you meant https://{url}?"
            )

        if not host:
            raise InvalidURL(f"Invalid URL {url!r}: No host supplied")

        # In general, we want to try IDNA encoding the hostname if the string contains
        # non-ASCII characters. This allows users to automatically get the correct IDNA
        # behaviour. For strings containing only ASCII characters, we need to also verify
        # it doesn't start with a wildcard (*), before allowing the unencoded hostname.
        if not unicode_is_ascii(host):
            try:
                host = self._get_idna_encoded_host(host)
            except UnicodeError:
                raise InvalidURL("URL has an invalid label.")
        elif host.startswith(("*", ".")):
            raise InvalidURL("URL has an invalid label.")

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