Are the Wii U eshop and the 3DS eshop cross compatible?

On steam, I have a single ID. No matter which system I'm on, my games follow me. I get the game on my Windows Desktop and I can then download it and play it on my SteamPC (assuming it's compatible with both systems). Or on my Mac (likewise).

If I own a Wii U and a 3DS, are the consoles joined by a single Nintendo ID? If I buy Super Mario Bros 3 on the Wii U, can I play it on my 3DS?

I know you can pay to upgrade a Wii Console game to a Wii U for a "nominal" fee. But I don't see any mentions about Wii U and 3DS cross compatibility and account inter-twinings.

Solution 1:

You can link a single ID to your 3DS and Wii U (this is a fairly recent change). But the games are not "cross buy" in any way similar to the Playstation ecosystem. You can upgrade Wii VC games to Wii U (only if they physically reside on the Wii U console), but buying [GAME] on Wii U, much less Wii, doesn't entitle you to [GAME] on 3DS even if [GAME] is on both. There's also no way to move save data between either system, with case-by-case exceptions (you can do this in Monster Hunter 3 U, but only because of a companion app, it's not built-in functionality like it is on Playstation 3/4/V)

The consoles are joined by ID, but really only for Miiverse, Club Nintendo and eShop balance purposes. This has been a common complaint about Nintendo's ecosystem but there have been no announced plans to change this on the current consoles.

Solution 2:

While you can share one Nintendo ID between your consoles (and one Club Nintendo ID as well, if you so wish to link one to your account), there is no cross-compatibility of games. Any funds you use attached to that ID, though, will be available on both systems.

As far as the actual shop content goes, the WiiU eshop and the 3DS eshop are considered separate entities - games you buy on one will not appear on the other (even if they are available on both shops). So if you want to play Super Mario Bros 3 on both the Wii U (if available) and on your 3DS, you are going to have to buy it twice, and the save files will not be the same.

Solution 3:

Additionally to what has been said already, if you own multiple of the same console, such as 2 3DS or 2 Wii U, buying a game on one system does not entitle you to downloading or playing the game on the other. The only way to make sure you get to play your previously purchased content on a new device is through a system transfer.

Transferring purchased games from a broken or bricked console to a new, working one can be quite a hassle and will almost certainly involve contacting Nintendo support.