Similar to the Netherlands, Denmark is a very Interrail friendly country. Denmark has many trains and reservations are (domestically) never needed, allowing for easy travelling by Interrail. The country is also discussed by both Seat 61 and Interrail.
Domestic travel
Validity
The Interrail pass is usually accepted within Denmark. Nationwide, the Interrail pass is accepted by state-owned DSB (Danske Statsbaner) and Öresundtåg. For local carriers, the Interrail pass is accepted by Lokaltog, Arriva and Nordjyske Jernbaner. The S-Tog operating in the Copenhagen area also accepts the Interrail pass.
The Interrail pass is not accepted by Midtjyske Jernbaner. Also, the Interrail pass is usually not accepted by Danish metro (e.g. Copenhagen metros) or tram/light rail services (e.g. Aarhus Letbane, the Aarhus-region tram network).
Reservations
Domestic trains throughout Denmark don’t require a reservation. It is however optional for the longer distance InterCity (IC) and InterCityLyn (ICL) trains. A reservation costs 30 DKK (~€4) per journey. Reservations can be booked at the DSB site. As the ticket for the train itself is already covered by the Interrail ticket, select 0 travellers and the required number of seats to only buy seat reservations.
International connections
SJ High-speed
Between Copenhagen and Stockholm, SJ operates a high-speed service with X2000 trains. For this service, seat reservations are required. The reservations can be booked at the SJ website. When entering the journey, Interrail passes can be added when selecting “Travellers” and then “Add SJ Prio/period ticket” where “Interrail or EUrailpass” is at the bottom of the list. It is recommended to book these trains in advance as these trains sell out frequently in advance.
When travelling from Copenhagen to Stockholm with SJ, keep in mind the train usually departs from platform 26. While this platform is not as far as the 15-minute walk signs in the station may make you believe, it still takes around 5 minutes to get to the platform. Especially when travelling with luggage, pay attention to the departure screens and be on time. Platform 26 can be reached by walking along platform 5/6, up the stairs, crossing the road and back down the stairs again. Seat 61 has provided pictures to visualise the walk to platform 26.
Öresundtåg
A regular and frequent service between Copenhagen – Malmö – Gothenburg. This train does not support reservations and are typically not needed either due to the frequent service operated with high capacity trains.
Germany
DSB and DB operate trains between Copenhagen – Hamburg and Aarhus – Hamburg. These trains accept the Interrail pass. For these trains, a reservation is required in the summer months (June/July/August, exact dates may vary) and highly recommended outside these months. Seat reservations for this service can be booked at DB, where “Seat Only” should be clicked at the bottom of the site when planned the trip.
Snälltåget
Snälltåget, the night train between Berlin/Hamburg and Stockholm, calls at Copenhagen. The Interrail pass is valid for this train, a reservation is required and can be made at the Snälltåget website where the box “I have an Interrail or Eurail Pass” should be ticked.
Ferries
When Interrailing, Stena Line offers up to a 30% discount of fare prices. In Denmark, this offer can be used when using the Stena Line ferry between Frederikshavn (Denmark) and Gothenburg (Sweden).