Best Free remote desktop software for windows?

Rust desk
- This. I left TeamViewer after they flagged me as commercial. I've been using them for my home computers and 3d printers for ever. Now I do rust desk
  
  They flagged me too, but i just contacted them and said I'm not. Got unflagged pretty fast.
  I only use it to support family members though
- FOSS or freeware?
  
  Well the first thing it says on their website is „the open source alternative to teamviewer“
- +1

Moonlight and sunshine. Best desktop streaming experience
- I set this up initially for gaming, but slowly am ending up using it more for remote than gaming...

VNC is the kind of the baseline remote desktop that works on pretty much any operating system. You can start there & then decide if you need specific features that the others have.
You didn't mention your own OS but it too probably already has support for its own remote desktop solution.
- Windows has its default Remote Desktop Connection that uses RDP (Remote Desktop Protocol), once enabled it will listen on port 3389. It is pretty solid and has a few features beyond VNC. Just be careful, you probably don't want to open that port onto the internet since every port scanner is scanning that port & looking for unpatched Windows vulnerabilities or insecure user/password logins.
  I use RDP myself for my Windows system but I need to SSH into my network before using it, so it's really RDP over SSH. If you're not going to go through all that at the very least change the port to something else so it doesn't get port scanned to death.
  .. TBH if you're not too sure about how to secure this stuff maybe Chrome Remote Desktop is the best option, at least it's secured behind your own Google account (hopefully that itself is secure and you have 2FA enabled).

I'm not sure if they are the best, but two good ones I know of.
Nomachine
RustDesk
And if some reason your using windows. Just use RDP.
- RDP is kind of limited because it's a virtual session. It's useful if you only need to do stuff while you're actively connected but you can't, for example, remote in and start an app or process going and then disconnect and have that app continue. When you d/c your profile is essentially logged out. Your activity also can't be viewed by a user on the remote system, if you needed to collaborate or assist somehow.
  UltraVNC has worked ok for me for windows systems. It has some of that open-source clunk to the UI, but is pretty straight forward and does what I need.
  
  What do you mean by logged out if you disconnect? I disconnect and leave sessions logged in all the time.
  
  RDP is kind of limited
  It’s useful if you only need to do stuff while you’re actively connected but you can’t, for example, remote in and start an app or process going and then disconnect and have that app continue.
  Sure you can, I do this all the time on the work RDP server. Maybe you need to tweak your group policy so it doesn't kick you out right away.
  When you d/c your profile is essentially logged out.
  Nope, depends on what group policy you configured. If you've never configured that before as a starter launch gpedit.msc (with admin privileges) and head to Administrative Templates / Windows Components / Remote Desktop Services / Remote Desktop Session Host / Session Time Limits. The other settings in there are also useful for other things you may want to configure.
  Your activity also can’t be viewed by a user on the remote system, if you needed to collaborate or assist somehow.
  Yes this is true, the only way to do that is to have admin privileges on the host and then take over that user session. But of course that's not collaboration, that's just you taking a user's current session without them being able to see what you're doing.
  On Windows the official way to do that is via Quick Assist (on Windows 10, not sure if it got renamed on Windows 11), it's sort of a shared RDP session where both the user and the remote user can share the same session. I've never needed to use it myself - with the work system users are pretty content with just having me "fix" whatever they needed without them watching, they usually don't care how to fix the problem themselves LOL.
  
  What? This just isn't true? I RDP into work all time and it picks up my user session with all open apps from the last time I was physically at the machine. Then next time I'm at the machine, it picks up the session from last time I remoted in. In other words, as long as you always use the same account, it's always the same session.
  Your activity also can't be viewed by a user on the remote system
  You are right this, but this is actually a benefit in my opinion. The last thing I want is for someone to turn on my monitor and see everything I'm doing. I like that it's a private session of sorts.
  Also RDP is better at adapting resolutions (I want my session to use my local monitors' resolution, not the remote one) and forwarding system key shortcuts than any other remote solution I've used.
- RustDesk says that it's compatible with Windows. Is RDP better still?
  
  Depends on use case. If your trying to remoting to a friends PC to help them do something. Rustdesk.
  If your remoting to your own PC. Say connecting to a windows machine at home from your work computer. RDP.
  Also as others have mentioned. Best to use RDP through something like tailscale or zerotier. So you don't have to open a port for it.

rdp over tailscale

If yoy need rdp, ssh, and vnc, i really like apache guacamole. If you want remote assistance software, i like rust desk.

Parsec if you're using it for windows

I like Tailscale and regular RDP.

I switched over to anydesk when TeamViewer started enshitifying itself, haven't looked back it works great on all my devices, even my phone (as in I can control my PC from my phone I use it a ton)
Setup is super easy, just make sure to set up proper passwords for it, specially if you use public wifi
- I remeber it used to be free for personal use, but it seems it's paid plan only?
  
  Maybe the Windows clients are paid now? But I use it currently for free on many Linux boxes. I haven't logged into one of the Windows boxes like my mother's office computer to fix something in a while.
  
  I use it for free in android Linux and windows sooo no, I'm not sure we're you're getting that info from
- AnyDesk has started enshitifying too but it's still better than TeamViewer.
- And it also supports port forwarding. Android client included.

RustDesk is good and open source too

TeamViewer, not a fan of the new interface, but it functions well.
I use it to help multiple family members.

I have had nothing but great experience from Parsec. It's gaming intended, but works perfectly for simple remote desktop use as well. Very low latency. Can start when windows boots, so you can even sign in remotely if you need to restart. Free

I use TeamViewer for occasional IT support and it does it fine.