Which countries can use the flag of united kingdom?

Only the United Kingdom is permitted to use the Union Jack as a national flag. Other countries, including those that were once part of the British Empire, are not allowed to use it as their own national flag.

However, there are some exceptions to this rule. For example, the Union Jack is included in the flags of some British Overseas Territories, such as Bermuda and Gibraltar, and is also included in the flags of some Crown dependencies, such as Guernsey and Jersey. Additionally, the Union Jack is used as part of the flags of some countries that have historical ties to the United Kingdom, such as Australia, New Zealand, and Canada. In these cases, the Union Jack is typically used as a canton, or upper-left quadrant, of the flag, and is combined with other elements to create a unique national flag.