Picasso Museum - Free Thursday

Others will probably have better information for you, but my anecdotal experience was when I went by the museum on the afternoon of a free day, I was told they had already given out all the free tickets for the day, and I was out of luck.

The Picasso museum is worth paying for. Don't miss it!

But don't assume you will necessarily avoid the crowds by going on a day when you have to pay. The place was a madhouse late in the afternoon when I went there in August 2016. Given that they obviously have capacity controls, I'm not sure the place would necessarily be any worse on the free day; you'd just need to get there early in the day to snag a ticket (for whatever time).

You need to really, really want to see that museum to put up with the conditions I faced. But it's obviously not that dreadful all day, every day, because occasionally someone posts on this forum that it wasn't all that bad. However, I think we can take it as a given that all the available tickets will be distributed on a free day, so I assume you would have the same sort of experience I did.

So: How much do you like Picasso?

If you go to the museums website you will find that you need to reserve a timed ticket for admission even on the free days. According to the site, you can only do this up to four days prior to the time you want to go. My guess is that they go fast. This won't help with the potential crowd problem, but you may at least be able to get in. I have been to the museum several times, and while always busy, there were times when I entered spontaneously just because I was walking by and there was little or no line. But I had the luxury of staying in a nearby apartment, and being in the neighborhood for over a month. If your time in Barcelona is short, you are taking a chance with no advance ticket.