Best free IPv6 address tools (expand, compress, split, EUI-64)

AdminKit is built by Netbase JSC. AdminKit is listed below; ipaddressguide.com, subnetonline.com, subnetcalculator.dev and ipbittools.com are independent and not affiliated with AdminKit.

What each tool’s own page confirms

ipaddressguide.com’s IPv6 tool, read 2026-11-07, states plainly that “this tool compress IPv6 address and vice versa” — a free, no-login page with two options, compress or expand, and nothing else stated on the page itself. It’s part of a much wider ipaddressguide.com suite of unrelated IPv4/IPv6 utilities, but this specific page does one job.

subnetonline.com’s IPv6 Subnet Calculator, also read 2026-11-07, is described on its own page as “an IPv6 Subnet Calculator for mapping your own hierarchical subnets,” useful for “converting complex, multi subnet networks from IPv4 to IPv6” — a free, no-login tool for planning subnets across a network, not for expanding, compressing or converting a single address’s interface id.

subnetcalculator.dev’s MAC to IPv6 Converter, read 2026-11-07, states it will “turn any MAC address into its EUI-64 interface ID and fe80:: link-local address — with every step shown,” and also offers the reverse direction on the same page (“Reverse: EUI-64 IPv6 address → MAC”). Its own page states it runs client-side with no signup, and the site hosts a separate IPv6 compression calculator for pasting an address directly rather than deriving one from a MAC.

ipbittools.com’s IPv6 EUI-64 Calculator, read 2026-11-07, converts a MAC address into its 64-bit interface identifier, showing the ff:fe insertion and the flipped universal/local bit, and its own page states it is “100% browser-based.” Its page is explicit that going the other way — pulling a MAC back out of an existing EUI-64 address — needs a separate “IPv6 address analyzer” tool on the same site, not this calculator.

AdminKit’s IPv6 info tool does all four of the above on one page: it expands a pasted address to its full 8-group form and compresses it to its RFC 5952 canonical form, splits it at a /64 or custom prefix into its network and interface-id parts, classifies its RFC 4291 address category (loopback, unique local, link-local, multicast, the documentation range, or global unicast), and converts a MAC to or from the modified EUI-64 interface id it would produce — entirely offline, with no DNS lookup, geolocation or ownership claim made about the result.

Does AdminKit’s IPv6 info tool replace all of these?

Not exactly, and that’s the honest framing this page uses. If you specifically need to plan multiple hierarchical subnets across a whole network, subnetonline.com’s calculator is built for that scope in a way AdminKit’s single-address tool is not. If you want a MAC-to-EUI-64 conversion with the reverse direction also available on the very same page, subnetcalculator.dev already offers that pairing. What AdminKit’s page adds is breadth in one place: a single paste box that handles expand, compress, split, category and EUI-64 (both directions) together, so you don’t need to know in advance which of these four narrower tools to open.

The honest angle

This isn’t a best-to-worst ranking. ipaddressguide.com is the fastest option if a quick compress or expand is genuinely all you need. subnetonline.com is the stronger pick for subnetting a whole network, not just reading one address. subnetcalculator.dev and ipbittools.com both convert MAC to EUI-64, with subnetcalculator.dev the only one of the four whose own page also reverses an EUI-64 id back to a MAC. AdminKit’s IPv6 info tool trades that per-tool depth for single-page breadth, covering expand/compress, split, category and EUI-64 conversion both ways without an account or API.

For a whole CIDR block’s network/broadcast/host-range math rather than one address, see best free subnet calculators and AdminKit’s own subnet calculator. For a MAC’s registered manufacturer rather than its derived IPv6 interface id, see MAC vendor lookup. The EUI-64 and link-local address glossary entries cover two of the concepts every tool in this comparison touches. AdminKit’s IPv6 info tool is part of AdminKit’s IP & network cluster, alongside the IP, subnet and MAC tools used in the same kind of address investigation.

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Trademarks belong to their respective owners; AdminKit is not affiliated with ipaddressguide.com, subnetonline.com, subnetcalculator.dev or ipbittools.com.