What causes "Cookie name cannot be empty" in SeleniumHQ/selenium?

Validate the name is non-empty and not whitespace before calling get_cookie.

SeleniumHQ/selenium · warning · ValueError

Cookie name cannot be empty

Error message

Cookie name cannot be empty

What it means

Raised by `get_cookie` when `name` is falsy (empty string) or is all whitespace (`name.isspace()`). The guard rejects these before issuing the GET_COOKIE command, because an empty name is ambiguous and some backends misbehave. It is a ValueError; the docstring documents this contract.

Source

Thrown at py/selenium/webdriver/remote/webdriver.py:754

            A list of dictionaries, corresponding to cookies visible in the
            current session.
        """
        return self.execute(Command.GET_ALL_COOKIES)["value"]

    def get_cookie(self, name) -> dict | None:
        """Get a single cookie by name (case-sensitive,).

        Returns:
             A cookie dictionary or None if not found.

        Raises:
            ValueError if the name is empty or whitespace.

        Example:
            `cookie = driver.get_cookie("my_cookie")`
        """
        if not name or name.isspace():
            raise ValueError("Cookie name cannot be empty")

        with contextlib.suppress(NoSuchCookieException):
            return self.execute(Command.GET_COOKIE, {"name": name})["value"]

        return None

    def delete_cookie(self, name) -> None:
        """Delete a single cookie with the given name (case-sensitive).

        Raises:
            ValueError if the name is empty or whitespace.

        Example:
            `driver.delete_cookie("my_cookie")`
        """
        # Firefox deletes all cookies when "" is passed as name
        if not name or name.isspace():
            raise ValueError("Cookie name cannot be empty")

View on GitHub (pinned to aa36b38e69)

Solutions

Validate the name is non-empty and not whitespace before calling get_cookie.
Default to None semantics: if name is blank, skip the lookup and return None yourself.
Strip and assert the name in a helper used by all cookie calls.

Example fix

# before
c = driver.get_cookie(name)  # name may be ''

# after
name = (name or '').strip()
cookie = driver.get_cookie(name) if name else None

Defensive patterns

Strategy: validation

Validate before calling

if not name or name.isspace():
    raise ValueError('cookie name required')
driver.get_cookie(name)

Type guard

def is_valid_cookie_name(name) -> bool:
    return isinstance(name, str) and bool(name) and not name.isspace()

Prevention

Normalize/strip cookie names from external sources before any cookie API.
Centralize cookie name validation in a helper shared by get/delete.

When it happens

Trigger: Calling driver.get_cookie(''), driver.get_cookie(' '), or passing a name variable that resolved to an empty string (e.g. parsed from a header/config that was missing).

Common situations: Dynamically building the name from a config/CSV that has blanks; forgetting to validate user input before lookup; off-by-one slicing that yields ''.

Related errors

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/e3bb0107d54d7dae. Report an issue: GitHub.