- URLs must always be lower case (to avoid incompatibility between Unix and Windows, respectively case-sensitive and case-insensitive)
- URLs must always be in English, even when they contain a page in another language (see also Language indicator)
- multiple words contained in a URL must be separated by a dash/hyphen (-), though the underscore (_) is also accepted
- URLs must not contain chained multiple words (e. g. europeancommission is wrong, european-commission is correct)
- URLs must not contain acronyms, as they are not understood by a broader audience. Exceptions can only be granted for existing URLs already approved in the past.
4th level domains in ec.europa.eu