MacOS – Wifi hangs on early 2015 MacBook Pro

The wifi icon (click here to see how you could have found about it on your own) is the top bar, right between the carrier and the clock, and it replaces 3G or E. It looks like this:

Like Alvar said, best way to be sure is getting in Airplane mode and turning wifi on.

As for youtube not working while others do, it's probably blocked. This could be on the wifi or on the iPhone, if it's a company phone with a provisioning profiles blocking it or if it's jailbroken and got a firewall on it. Just check if youtube works on any other device on the same wifi and you'll know for sure where's the issue.

If youtube is just running slow, but it is running, it could also be your other heavy sites are cached. Without more info I can't think of more options for that issue.

I was having a similiar issue with 10.10.3 which was not corrected when I updated to 10.10.4. Many, many things were tried before I got it to stay connected to WiFi reliably, however deleting the networking PLIST files seems to be what finally did it.

The Fix:

• Disable WiFi
• Open Finder
• Press Cmd+Shft+G to go to the folder /Library/Preferences/SystemConfiguration/
• Delete (or move) the following files:
  • com.apple.airport.preferences.plist
  • NetworkInterfaces.plist
  • preferences.plist
• Restart your computer
• Re-enable WiFi

The Other Things I Tried:

• Reset PRAM
• Reset SMC
• Used Onyx to clear caches, run update scripts, etc.
• Disabled AirDrop by using Terminal to run sudo ifconfig awdl0 down
• Kext Utility to reset kext permissions, followed by...
• Disk Utility to verify/correct permissions.
  • In my case errors were found, and I had to...
  • Reboot in Recovery Mode (press Cmd+R as boot sound, hold until you see the Apple logo), use Disk Utility, however no errors were detected
  • Disabled FileVault, waited for decryption to complete
  • Reboot in Recovery Mode, use Disk Utility, some errors corrected then return value 8 and was told I had to backup, format, and restore to the drive.
  • Ran Disk Utility repair again and no errors were detected (then I ran it again for good measure)
  • Rebooted and Disk Utility found no errors.
  • Still had WiFi disconnects...
• Deleted the AirPort plist files (fix above) and WiFi has been stable.