Best train app for Intercity, regional, and intercountry trains?

no matter which app you use it will be the same trains on the same tracks, mostly operated by different branches of DB.

Use the DB app - it is very good.

For the Austrian trains use the Oebb (Öbb) or if you are in the right place at the right time have a look at Westbahn. They have a most excellent webpage but no app that I know of.

I rely almost exclusively on DB for travel within Germany... but OEBB is useful as well whenever Austria is involved. I have no issue with schedules at either. Route maps appear with any DB itinerary you pull up. As for detailed railway maps for all of Germany... The network is incredibly dense. I don't know of a good one online. It's probably best to hunt down maps by individual "Land" (state.) Here are some covering southern Germany which I keep links for:

Bavaria

Baden-Württemberg

Rheinland-Pfalz u. Saarland

Hessen

And here's one I have for Austria, which I know to be incomplete.

DB Navigator app is a good aggregator of offers - not only offers from DB. It allows also to filter results by "consider only D-ticket". Some comfortable functions are in as well, e. g. self-check-in to a booked long-distance train when you found your reserved seat.

A look into Flixtrain offers are sometimes a good idea. They increase offering and market share in German market. Flixbus has also a wide range of destinations and connections offered.

The Omio app has good ratings. The Berlin located team learned a lot and is also able to compare different means of transport between two destinations.

One to " The DB trains are notoriously unreliable": there is a big difference between long-distance and regional trains. Also on long-distance some connections are more affected than others. So, do not let your hope die before taking then train - without or with delay.

Just to give you an impression on how much work and traffic is done on the rail network in Germany:
"We have the planning and financing security we need for 2026 to continue driving forward the renovation work at full speed. The key challenge remains reconciling train operations and construction work. We anticipate 28,000 construction sites and at least the same level of operational performance, amounting to over one billion train-kilometers. By the end of 2025, 530 railway companies, operators, and shippers will be active on the German network."
Source and more details: DB press release from Dec 28, 2025; translated with DeepL.com (free version)

Have a good journey.

Mark, does tge DB website show/sell tickets for the RegioJet and Westbahn trains?

Also on long-distance some connections are more affected than others.

And do you have a list of the reliable routes?

does tge DB website show/sell tickets for the RegioJet and Westbahn trains?

RegioJet is not active in Germany despite repeated declarations of intent. As far as Westbahn and Flixtrains are concerned, the DB website shows their trains but does not sell tickets for them.

And do you have a list of the reliable routes?

This would be pointless, because the railways are like the Hydra of Lerna: as soon as one construction site is closed, two new ones open elsewhere, often on very short notice by the network operator InfraGo. This makes life difficult not only for passengers but also for carriers. InfraGo claims that construction capacity is often only available at short notice, but its critics say that they simply wait until prices are at their lowest and don't care about the consequences of their actions. The only thing you can do is find out about the construction site situation before you travel.

And do you have a list of the reliable routes?

Fritz, that was in response to Mark’s comments above. It doesn’t matter if some of the routes are reliable if you don’t know which routes those are; you just have to assume they will all be unreliable.

RegioJet is not active in Germany despite repeated declarations of
intent. As far as Westbahn and Flixtrains are concerned, the DB
website shows their trains but does not sell tickets for them.

I asked because DB does list and sell tickets outside of Germany (I can buy a Vienna to Budapest ticket on DB for instance) and the OP was looking for something like The Trainline to be able to see all of the options in one place. Or that was my perception of the question.

And do you have a list of the reliable routes?

Better: with Zugfinder travelers can have all historical delay data for long-distance trains available for retrospective viewing, as well as delay forecasts to help travelers plan your next train journey: the train search function allows users to view data from the last 30 days (and up to 2 years).

There you can also lookup the top 100 delays of a day.

There are also additional sources which show / list the most affected connections (example) but I doubt that this has any relevance for the future expectations because the influencing factors and dependencies in the system are changing on a daily or weekly base. Very often only parts of a long-distance connection are affected, not the connection in total.

Mark, for all that information, dont you have to pay for a membership?