IPv4 in IPv6

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IPv4 in IPv6

The four ways a v4 address is written inside a v6 one, both directions.

It runs entirely in this browser tab: the addresses, names and passwords you type are never uploaded, and the tool makes no network request while it works. Open your browser's network panel and try it — nothing leaves the page.

Settings

Which mechanism
Which of the four ways to write a v4 address inside a v6 one. Reading back the other way recognises all four. Choices: Mapped, Compatible (deprecated), 6to4, NAT64.

How to use it

  1. Paste your text into the box above, or open a file.
  2. Adjust the settings beside it until the result is what you wanted.
  3. Copy the result, or save it as a file. The result updates as you type.

Questions

Does this look anything up?
No, and that is the point of the group. Nothing here resolves a name, queries a registry or opens a connection. Three tools would want a table bigger than the whole application — the vendor prefixes, the routing table, the full port register — and each of them takes the table from you and says so rather than answering "unknown" about something that exists.
Why does the subnet calculator show the bits?
Because a prefix stops being a mystery the moment you see it written out. It is also where the two lengths everybody gets wrong become obvious: a /31 is a point-to-point link with two usable addresses and no broadcast, and a /32 is one host rather than minus one.
Can I paste something confidential in?
Yes, and that is why the group is built this way. An internal addressing plan, a DKIM private key's public half, a Wi-Fi password and an authorisation header are all things you would think twice about typing into a website. None of them is sent anywhere, and the request builder hides credentials by default so that what you paste into a ticket is safe to.
Is what I type uploaded anywhere?
No. This page carries the whole tool as WebAssembly and runs it on your own device. You can watch your browser's network panel while you use one.

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