IPv4 vs IPv6: Why Both Exist and Which One You're Using

IPv4 ran out — IPv6 is the replacement. Learn the difference, how to see which you have, and why some sites behave differently on each.

Why two versions exist

IPv4 (e.g. 203.0.113.8) has ~4 billion addresses — exhausted years ago. IPv6 (e.g. 2001:db8::1) has effectively unlimited space and is the long-term replacement. Both run side by side today (dual-stack).

Which one are you using?

Check our IP tool: four dot-separated numbers means IPv4; longer colon groups mean IPv6. Most homes still browse over IPv4 with IPv6 available underneath.

Why it matters for troubleshooting

Some outages hit only one stack — a site loads on IPv4 but stalls on broken IPv6 (or vice versa). If a site fails on one network but works on mobile data, suspect a v6/v4 path issue and test both.

Test it now: run a live check → then re-read your result with this guide. Each check + guide read is another pageview that funds the free tool.

FAQ

Should I disable IPv6 to fix a site?

As a 2-minute test, acceptable; as a permanent fix, no — report it to your ISP instead.

Is IPv6 faster?

Slightly, sometimes (no NAT, shorter paths) — but rarely the reason anything feels slow.