Can we cover both Disneyland parks in Paris in one day?

No. Not if you're the least bit serious about it (sure, you can run through).

I did Euro Disneyland shortly after it was opened (there was only one park at that time, and it was about half the size) when it was mostly devoid of visitors and the parking lot looked like the backside of the moon.

It was a rainy, cold day, there were maybe three dozen people altogether in the entire park besides my poor freezing girlfriend and me (read as: no standing in queue, zero waits). We didn't do the whole park in one day. I can't imagine doing a park twice the size in a day, let alone two of them.

It depends very much on your attitude and how thorough you need to be.

Yes, you can decently cover both parks on lower crowd days provided you're willing to forgo some attractions if necessary.

• Be sure to get familiar with the FastPass system.
• If you stay at a Disney hotel, you get Extra Magic Hours where they let hotel guests in ~2 hours before regular opening.
• Walt Disney Studios is much smaller so if you do go for both, go there first, see what matters to you, then spend the rest of the day at Disneyland.

You can't nearly cover all the good rides in 1 park (for anyone on any given day) in 2 days, so doing all of that in 1 day, would be a stretch. However, it does depend on your attitude, and what you're trying to get out of the experience.

You will get phenomenal Disney thrills within 1 day and 2 parks, but of course, be prepared to give up a few solid attractions.

Tip: Learn about the Fast Pass prior to heading over, and make full use of it.

You most defiantly can!

BUT it depends on the time of year (We went mid September) and on what you are willing to miss. I went with my partner, we got there an hour before opening and as soon as the gates opened we immediately ran to the most popular ride at the time (Finding Nemo) which meant we got on it straight away.

After that we got on every other large coaster a couple (or even three or four) times throughout the day just watching the boards for which had the lowest wait. The only thing you may have to miss is some of the shows like the stunt shows but we weren't interested in that anyway. We managed to see the character parades throughout the day though and we just hit the roller coasters until the final fireworks at around 10-11pm.

My partner being a massive Disney fan meant we weren't there just for the roller coasters and saw pretty much every corner of the parks in the one day.

It is definitely a long day if you want to get around everything but it is totally worth it! Have fun :)

You'll miss out on some stuff, and the overall experience, but it can be done. It's harder on a first visit because you won't have time to get your bearings.

A few more suggestions to speed through the parks:

• Don't eat at peak times. We term this a two-lunch strategy, having something at about 11 and again at 3. Just when the queues for food get long, the queues for rides stop growing or even shrink.
• Alternatively bring food you can eat in the ride queues. This saves you having to queue up to buy it (and is cheaper). There's not much available in the park that's portable enough to eat standing in queues. A minor downside is longer at the bag searches on the way in (this can become a bigger difference if you can skip the bag search by not having a bag, dpeending on how they're running those gates).
• Of the roller coasters, Indiana Jones has the shortest queues late in the day, and is a bit of a walk from the other big rides so you don't want to be rushing to and from it.
• Go midweek, checking the opening hours carefully, and avoid school holidays, (check the French term dates).
• Check the wait-time boards (last time we went to Studios, but not the main park there was an app with wait times, but it wasn't working very well, so look in to that too).
• Do your souvenir shopping on the way out or in the Village after chucking out time.

Yes, with careful planning.

I should mention that Disneyland Paris does frequently have closures when rides are closed for refurbishment. You should look up what will be open when you go and plan accordingly. I believe dlprmagic (or whatever it's called) lists closures, alongside Disneyland Paris' main site.

We went back in 2014. At the time, Crush's Coaster, Indiana Jones, and Captain EO were closed, and Ratatouille hadn't opened yet.

We arrived at 4pm and managed to do all that we wanted to do in Disney Studios by closing at 6pm. This included Aerosmith, Tower Of Terror, RC Racer, and the Studio Tram Tour.

We then moved to Disneyland Paris itself for the last two hours, and managed to get on Space Mountain Mission 2, Big Thunder Mountain, and Pirates Of The Caribbean before the Disney Wishes firework show and closing at 8pm.

The next day we went back and managed a fair few more rides, solely at Disneyland Paris. This included several re-rides on Space Mountain and Big Thunder Mountain, Phantom Mansion, Buzz Lightyear, and just about everything else (even the sedate little rides in Fantasy Land). There's also a lot of places to explore in Disneyland Paris (caves under the castle, the Aladdin alleyway in Adventure Land, Captain Hook's galleon and that area, Alice's maze, the fort in Frontier Land, Captain Nemo's submarine - there's loads to explore there that you won't find in the US parks). Eventually we gave up at about 5pm, shortly after Disneyland Paris' tiny parade (nowhere near the size of the Magic Kingdom one).

However, this was in March, and outside of a lot of school holidays. It wasn't that crowded - Space Mountain was a 5-10 minute wait, and most rides were about the same except for RC Racer and Big Thunder Mountain (25-30 minutes). Also, it was just myself and my wife, and we're pretty hardened park junkies. As others have suggested, use Disney's fastpass system (it's free! You can go to the small ticket machines near the more major rides and get a fastpass to come back at a particular time to skip a lot of the queue - though you can only have one of these at once!). Consider an early lunch, at 12 or a bit earlier if you can to avoid the lunch rush and keep riding whilst others eat. And for dinner, consider just waiting until you're done at the parks if you're able (there are a few dining options in the Disney Village).

It depends on your aims.

If you want to spend the most time on the rides and attractions, then there will be plenty to keep you busy in a single park (especially the main park).

If there are particular attractions that you're really interested in, then you will have time to visit both parks.

If you are short on time, then don't bother with Crush's Coaster because it always has long queues. You could queue up outside Studios before it opens, but you'll get more done if you use that time in the main park during their Extra Magic Hours instead (if staying at a Disney hotel).