IPv4 Range Expander

Takes CIDR, hyphen ranges, or plain addresses — mix them in one paste

The common use case is generating an input list for a scanner or firewall rule. You paste in whatever you have — a /28 here, a start-to-end range like 10.0.0.5–10.0.0.37 there, maybe a handful of individual IPs — and click Expand. It processes everything in one go and builds the full list in address order. A /24 gives you 256 lines, a /16 gives you 65,536. The preview shows up to 1,000 lines so it doesn't lock the page, but when you download the file — plain TXT or CSV — you get the entire set, not just the preview portion.

Why there's a 16 million address cap and how to work around it

Trying to expand a /8 in a browser tab is a bad idea. Over 16 million addresses would take long enough to freeze the page and produce a file most tools can't easily load anyway. The cap is there to stop that from happening accidentally — you'll see an error message telling you the range is too large. The practical fix is to split it: expand individual /24 blocks and either concatenate the files afterward or feed them to your tool one at a time. For nmap that means -iL with each file in sequence, which is actually more controllable than one giant list.