ETA electronic travel authorization required
For Danish citizens traveling to Great Britain (England, Scotland, Wales and Northern Ireland), an electronic travel authorization (ETA) is now required.
This came into effect on April 2, 2025.
The ETA is a pre-authorisation that allows travelers who would not normally be required a visa to enter the UK for shorter stays (up to six months).
It is important to note that ETA is not a guarantee of entry, as the border control control must still be approved.
See more https://www.gov.uk/eta