Note that you often don't really need a travel adapter. E.g. you can fit in EU plugs into UK, Swiss and Chinese plugs.

How would it "detect" what country it is in? And some countries have multiple sockets, so even knowing which country would not absolutely determine which pin to use. That is something you, the traveler, need to manually determine, then select pins. And the universal devices usually provide the most common pin configurations in the space allowed. To cover every possible pin config would make the device not so portable (especially if it does volatge as well like your fantasy mentioned).

@JonathanReez - plugging a power plug into an incorrect socket is not good advice. The pins and spring contacts do not make good contact leading to potential for sparking. Buy an adapter for a couple of dollars and decrease the risk to yourself and everyone else staying in the lodge you are trying to burn down.

@Tom if you keep an eye on the socket it's not a problem. Obviously an adapter is better, but personally I never bother carrying one for the UK.

@JonathanReez - Maybe you are contentious enough to keep an eye on things, but most people are not, so advising that course is not good.

@JonathanReez I would not recommend doing that at all. Keeping an eye on the socket is not even enough; as you might damage it in such a way that subsequent normal plugs plugged into it don't make contact properly and start a fire. Unless you're expecting all power sockets even with normal plugs in to be supervised at all times, this is very dangerous advice.

I used to think like you did, OP. But it turns out that most multi-country adaptors are beyond shonky; I've owned several with very dangerous features, most of them lacked earth continuity, most didn't have a fuse (necessary for safety for plugging non-UK appliances into the mains in the UK), and they're often by necessity of flimsy construction to allow all the different designs to be stored in a compact form. I would highly recommend buying a good solid single-purpose adaptor for each country you're visiting that is well-built and complies with relevant standards for both countries involved.

@Muzer a UK socket won't be damaged by an EU socket - the pins are the same. The only difference is that you push open the ground pin before inserting the plug.

@Muzer the EU pins are smaller, so they won't damage anything. I'm all for safety but this is too paranoid.

@Muzer let's continue in chat if you wish

The inside edges of the pins of UK plugs are 15.8mm apart; EU ones 13.5mm. The pins on EU plugs also bend inwards so you're pushing the contacts on the inside of the socket more than they're designed for. Add to this that many EU devices will still expect to be earthed and by this method you're just bypassing earthing. I'm sorry, just shoving a random plug into a socket it's not designed for is risky. BTW, can I copy my second comment (not part of this discussion) back to the post?

Oh, and I forgot to mention, it also leaves your plug without a fuse. Because of the way UK mains is wired up (different to almost every other country), there's much higher risks of faulty devices drawing enough current to set the plug or cord itself on fire, and so, plugs need fuses. EU plugs aren't going to have fuses.

My laptop adapter and USB charger have a fuse as well

Or at least would break gracefully without destroying my phone or my laptop

I don't carry other devices

the part about the UK plug is true. I was wrong

@Muzer I'm not sure what you want to copy or where. Feel free to add an answer jnstead