top iPhone 8 internet speed?

The iPhone 8 supports 4G/LTE, so the limit will be the network, not the phone. I have gotten up to 90 mbps (rarely), but generally 20 - 40 mbps.

My iPhone 14 on T-Mobile 5Guc has been as high as 650 mbps, but even on plain vanilla 5G I’ve gotten over 100 mbps.

iPhone 8 supports 802.11ac, which at the time of the 8 introduction could be up to 1,300 Mbps or 1.3 Gbps.

Of course, your ISP would have to be delivering those speeds and the Wi-Fi router would have to be capable of handling those speeds. The iPhone 8 would have to be very close to the router as well.

Most routers that claimed 1,300 Mpbs speeds typically checked out at about 700-800 Mbps.

Real world, the iPhone 8 might check out at 500-600 Mbps on a great day.

Cellular data, best the iPhone could do on an LTE or 4G connection....I don't know, but I would be surprised if it was much over 50 Mbps if that.

Theoretically, in the best circumstances, with no interference or blockages of any kind, and appropriate wwi-fi router, 1.3Gbps on 802.11ac Wi-Fi.