If WW3 breaks out, what countries are going to be on which side?

Canada, Europe, Ukraine vs Russia and Belarus

America, Japan, Taiwan vs China and North Korea.

Israel will use the opportunity to fully genocide Palestine, expand into Lebanon and Syria sparking a regional conflict there.

India vs. Pakistan

In practice, some countries will lose rapidly once the nukes fly and a lot of people will die.

It'll be a cold war against the US. Europe and Latin America vs China, Middle East, Africa.

The US will probably just dissolve into civil war

I call vice president I'm freaky enough to do it

It will not be a war between the major super powers but a break up of the globe along those lines.

The US will continue its war on South American, mainly Venezuela right now. Russia will continue to chip away at the EU and push into their territory. China will take Taiwan, but mainly just focus on making money off both fronts. Africa will continue to be exploited by US/Russia/China.

We'll all be on the losing side, that's for sure.

Unfortunately spot on.

I’m on the side of the poor, weak, disabled and oppressed.

That is everyone in my orbit. F yeah 🙌!
- Well, the cool thing about life is that despite humans making up stories that declare themselves the pinnacle of it, when every human is wiped out, life won't care and will flourish without them mucking up the works.
Uh... So, you're on the side of Russians? Wut?
- redacted
- Why don't presidents fight the war? Why do they always send the poor?
Edited title to reflect the question is about countries, the groups that actually control the militaries, vs demographic groups.

If WWIII breaks out we're all gonna fucking die. Will there be any countries left after 24 hours?

new Zealand
- Isn’t there a movie with that premise? They survive but have to watch over a few months as radiation in the northern hemisphere works its way south. They’re already dead but have to wait months for it to happen
Good chance yes non-aligned nations.

It is possible that WW3 has already broken out, but is not called that way yet. WW2 was not immediately called WW2 either. It took some time for it to grow to the dimensions that enabled it to be called a World War.

As in the previous two world wars, some countries will be switching sides. Just like USA has been doing now, hopping between the side of the Russia and the side of humanity about once per week, depending on how their president is feeling about things each morning.

If we are currently in WW3, then the sides are very confusing:
USA is against China but on the side of the Russia.
China is on the side of the Russia but not really against anyone. Except its own minorities?
EU and UK are against the Russia but not against USA or China.

Yeah I think it’s reasonable to assume that it could have started but we don’t know about it yet.
Some people argue that WW2 actually started in the early 1930s with Japan’s incursions into China which ultimately resulted in the second Sino-Japanese war. In 1932 that probably felt a lot like Russia and Ukraine felt to us in 2022. I think the real deciding factor on whether it spirals into a global conflict is the extent to which a bunch of regional conflicts combine into to a global clusterfuck. US shit in South America is not helping. Neither did Israeli shit in Palestine.
We have always been at war with them
- I love how they claim Antarctica, like those penguins are defending the beachheads.

WWI started with the assassination of a national leader that most people had never heard of, but it dominoed throughout the world into a conflagration that killed millions.

A nuclear war is more likely to start like that. Some dumb country gets their hands on a nuke or two, and what fun is a shiny new toy of you can't play with it? Once one goes off somewhere, it could spread fast, as nations either defend themselves, or seek revenge.

Basically the movie House of dynamite

That depends on when it will break out. If it's tomorrow, China and Russia will be buddies or at the very least will be in a non-aggression pact situation. Most of Europe will side against Russia but might be more mealy mouthed towards China (even if they decide to start it by going after Taiwan and that escalates from there). The US will, as it is tradition in a world war, not enter until much later or unless attacked first. And on whose side? Depends on one person's bowel movement on that day an no longer on treaties and commitments. One of the many crucial areas to watch will be if the US honors the security alliance with Japan.

I say it depends on when because if we give it another 25-50 years, attitudes may shift. The US could try going for a more sane leadership and affirm its NATO membership. Sentiments towards Russia may shift in Europe, especially if the US is progressing further towards Idiocracy.

The US will be bankrolling Russia. Russia is weak and poor. The only reason they're still in Ukraine is China. And once they've conquered that, the US will happily help them invade the rest of Europe.

The empire-ambitious Axis of convenience: US, Israel, India, China, Russia, various Islamic kingdoms etc vs. whoever is willing to get in their way.

I'm from New Zealand. We've traditionally been a US ally but the situation being what it is at the moment, I think there's a good chance we'd try to stay neutral.

New Zealand will go where its billionaire expat refugee community tells it to go.
Sorry bro. Not gonna happen.
Australia and NZ really have to stand together just because of the geography. Australia is critical to NZ's security. If a superior force conquers Australia, then NZ wouldn't be able to resist in isolation. Logically then it will always be in NZ's interest to stand along side Australia.
Similarly, Australia needs a bigger more powerful friend to stare down our neighbors like Indonesia and bullies like China. That friend has been the US for the last 70 odd years, and with AUKUS that alliance will be greatly strengthened.
In any conflict since the dawn of time people have wistfully hoped that their own clan or tribe or city or country could stay neutral, but the reality is that to maintain your neutrality you need to be strong enough to defend yourself without assistance.
- Australia's biggest trading partner is China. It's absolutely against their interest to have any kind of conflict with China. But being a puppet state of the US, they're probably gonna do that anyway.

If the U.S. started the Great War Part III, it would probably be due to an invasion/takeover of a Russian-aligned country (e.g. Iran)

If Russia began the third big one, it would probably be due to either a) invasion of another European country (e.g. Finland, the Baltics) or b) some huge scandal that may or may not be truthful where American/European/NATO/whatever spies are found in Russian soil, prompting a justification to declare war.

If China were to start the war, it would almost certainly begin with either the hot topics of Taiwan or the South China Sea. I doubt the Chinese would risk a war for either though, and would only go in when the U.S. are distracted in some other war (e.g. if Trump goes in on Venezuela)

edit: or it could be over natural resources. Again.

China would go to war to protect their energy supply. If the US and Russia+Saudi team up its game on. Looks what's happening now...
- Wars over natural resources have unfortunately always been a thing with humans. Especially troubling given that we have created all sorts of fun ways to destroy entire populations...

I'm on the side of the Vietnamese

Pho around and find out.

I'm not sure about country alliances, but I do know that both the US and PRC will declare me as an enemy and "traitor".

I'm gonna go through what Japanese Americans experienced during WW2

Ever been to Vietnam? It's quite nice, and they're going to remain neutral in any coming conflict.
Come up north.
- They'll happily take my nursing degree but I'm not leaving without hubs and he has an old weed-related charge that would probably impair immigration to another country.
- I doubt they'll let me stay long term outside of the visa free X number of days
  Not enough proof

The "sides" that the countries take is of secondary importance. Capital will benefit from any conflict, no matter what the stated sides are, and suffer minimally. That's the true enemy

See, that's the thing. We had WW3 in the 1970s. Hitler came back, and he was riding a dinosaur, and Ghengis Khan was disco dancing the night away!

But you never heard about it because we have time travel, and decided that was a stupid timeline.

Oh, also, none of this timeline exists either. We deleted from existence in 2012.

The real timeline? Bernie Sanders won the 2016 and 2020 elections. Covid was a much easier thing to stop, because people got vaccinated.

And Dorritos bought Taco Bell, and IMMEDIATELY went bankrupt.

See? Everything is actually better now. You just never got to experience it.

Doritos did actually buy Taco Bell, in a sense.
Edit: that link still makes you do some digging, but here’s the Taco Bell part

Russia and China being allies is a given. Iran and the DPRK will be on their side too.

Israel, the USA, Japan, and parts of Europe will no doubt be on the opposite side, with the more sensible parts of Europe staying out of it.

India I have no idea, they're nominally a USA ally, but I could also see them trying to stay neutral.

China world no doubt take the opportunity to reclaim the island of Taiwan.

I imagine a lot of Arab states would try to remain neutral at first, but Israel would probably take the opportunity to invade the rest of Syria, at which point some may be dragged into the conflict.

India US relations have gone cold since Trump. Particularly with the +25% tariff for buying Russian oil which they perceive as unfair since
India followed the US in sanctioning Iran in 2019 which is why they increased purchases of Russian oil.
The West had set a price cap on Russian oil after the Ukraine war as everyone understood that completely banning its purchase would drive oil prices up undesirably.
The Biden administration was explicit in acknowledging and accepting that India buy Russian oil. It was seen as necessary to stabilize the market.
China buys more oil than India from Russia and faces no specific additional tariff.
The EU continues to buy gas and the US buys uranium from Russia (which also allows them to continue to finance the war).
The IMF (which is seen as an American/Western institution) continues to bail out Pakistan and the peception in India is that some of those funds will reach non-state actors who will perpetuate violence in India.
There are actually more reasons but India recently hosted Putin for a state visit and rolled out the red carpet for him. India and Russia have historically had good relations (the Soviet Union used its UN security council position to support India against postcolonial Western interference on several occasions) but this was friendlier than many were expecting and it is in large part due to the current US administration being inconsistent on trade policy and incompetent at diplomacy.
India's official stance is 'strategic autonomy' or multialignment but at least right now it seems to have more friends in the East than in the West.
No, the US will not be on the side of Europe.

Russia attacks EU, US stay neutral, US stay neutral, China leverage on Russia being busy to invade Eastern Russia, the conflict spread to former colonies where Russia, China, France, UK are already in cold war. Meanwhile, Turkey finally attack Greece, and Iran takes the opportunity gain influence most likely with their spy network.

As usual, America stays neutral, until US get dragged in the war (Taiwan or Israel) while Argentina wait for the last day to formally declare war. Not sure whether Japan would invade China or take back the Sakhaline island

TL/DR : Russia/Turkey/Israel versus EU/China/Iran.

As you see I am absolutely not an expert

To borrow the terminology from WWII, I imagine the Allies might include most of Europe, Japan, South Korea, Israel, Canada, Australia, and New Zealand

I'm betting the Axis countries might include Russia, China, and Iran, possibly Belarus, Hungary, and North Korea, along with partial or total support from other BRICS countries.

The US is kind of a wildcard right now. My first instinct is that they'd align with their closest long-time allies such as those listed above, but with Trump's affection for Putin and alienation of such allies over the last year, I'm uncertain. Trump could also simply choose to remain neutral, so as not to oppose Putin.

The US was neutral during WWI and WWII until they were attacked directly, so while it's easy to assume the US would be involved in the next world war, it might not be until it's forced to be, if at all. It's probably safe to say the US would at least be sending its allies military aid during the war. As long as no one messes with their shipping or attacks its land, the US might choose to get no more involved than that.

Honestly my money is kind of on the US starting the next one.
- Well, if history tells us anything, it'll probably be Germany again /s
  In the case where the US really does start WWIII, it would definitely throw a wrench in where countries fall in alignment. If the US were to invade one of its neighbors like it's threatened to do, that could be all it takes. It could be all the countries I listed against the US, for all I know. The only country that I think would support the US no matter what is Israel. I think the US would certainly have a hard time taking them all on. Then again, a world war has never involved a world superpower on the scale we have today, so it's hard to say what the outcome would be, but I'd expect the US would still probably lose if it was them against the world. Although, taking the fight inside the US would present some significant challenges to overcome owing to geography, besides military obstacles.