I have had my MacBook Air for about a year and a few weeks ago the internet has been lagging, I have tested 3 different routers from different homes and the internet was extremely slow with all 3 different networks everything else seems to be working fine, besides the App Store, it won't load and just says there is no internet connection, even though the the laptop says there an internet connection.
MacBook Air
Are you trying to connect using WiFi? If so check out this Apple article for troubleshooting WiFi issues.
https://support.apple.com/en-us/HT202663
How does the laptop behave if you connect the MBAir directly to the router with an Ethernet cable and Thunderbolt to Ethernet adapter?
Try booting into Safe Mode which will disable any unnecessary drivers, Startup and Login items.
Edit: You may want to run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper.
Are you trying to connect using WiFi? If so check out this Apple article for troubleshooting WiFi issues.
https://support.apple.com/en-us/HT202663
How does the laptop behave if you connect the MBAir directly to the router with an Ethernet cable and Thunderbolt to Ethernet adapter?
Try booting into Safe Mode which will disable any unnecessary drivers, Startup and Login items.
Edit: You may want to run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper.
Slow internet on MacBook Air
