Can you use an 8-string guitar string set on a standard 6-string guitar?

An 8-string set is not automatically incompatible: what matters is which six strings you choose. Check their individual gauges and lengths rather than relying on the number of strings on the packet.

The extra heavy strings may not fit your guitar’s nut slots, bridge or tuning posts. Tension depends on gauge, scale length and tuning, so using strings from an 8-string pack does not automatically cause excessive tension; attempting to tune very heavy strings to standard pitches could, however, be unsafe.

For straightforward replacement, choose a six-string set suited to your current setup. The Stringjoy Signatures Balanced Light Plus Gauge (10.5–50) set is one option to compare with your existing gauges, while the electric guitar components and strings guide offers broader selection advice.