IPv6 Expander
Free IPv6 expander and compressor. Runs 100% in your browser.
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What is IPv6 Expander?
The IPv6 Expander is a free online tool that converts IPv6 addresses between their compressed shorthand and the full 8-group expanded form. IPv6 addresses are 128 bits long but are usually written in a shorter form that drops leading zeros and collapses a run of zero groups into a double colon. This tool expands those addresses back to the complete 8-group notation, re-compresses them into canonical RFC 5952 form, identifies the address type, and breaks every 16-bit group into hex, decimal, and binary.
Key Benefits
- Restores the complete 8-group form that firewalls, routers, and config files often require
- Normalizes addresses to canonical RFC 5952 for consistent logs, DNS, and comparisons
- Catches malformed input that could break network configuration
- Identifies address scope: loopback, link-local, unique local, multicast, or global
- Breaks each group into hex, decimal, and binary for learning and debugging
Common Use Cases
- •Expanding shortened IPv6 addresses before pasting them into router or firewall config
- •Normalizing IPv6 addresses in DNS records, logs, and inventory systems
- •Debugging connectivity by inspecting each 16-bit group
- •Teaching IPv6 notation, zero compression, and address types
How to Expand an IPv6 Address
- Enter an IPv6 address: Type or paste any IPv6 address, compressed (2001:db8::1), full (2001:0db8:...), IPv4-mapped (::ffff:192.0.2.128), or with a prefix and zone ID.
- Read the two output forms: The expanded form shows all 8 groups with leading zeros. The compressed form follows canonical RFC 5952 rules using lowercase hex and the longest zero run replaced with a double colon.
- Check the address type and breakdown: The tool labels the address type (loopback, link-local, unique local, multicast, IPv4-mapped, documentation, global unicast) and lists each 16-bit group in hex, decimal, and binary.
- Copy the result you need: Use Copy on either output to take the expanded or compressed form, including any prefix or zone suffix, straight to your clipboard.
Key Features
- Expand compressed IPv6 addresses to the full 8-group, zero-padded form
- Compress full addresses back to canonical RFC 5952 notation
- Strict validation with clear error messages for malformed input
- Address type detection: loopback, link-local, unique local, multicast, IPv4-mapped, and more
- Supports /prefix lengths, zone IDs, IPv4-mapped tails, and URL bracket notation
- Per-group hex, decimal, and binary breakdown table
Frequently Asked Questions
What is IPv6 expansion?
IPv6 addresses are 128 bits wide and normally written as 8 groups of 4 hex digits. In their compressed form, leading zeros are dropped and the longest run of zero groups is replaced with a double colon (::). Expansion restores the full 8 groups by re-adding the zeros.
What is canonical RFC 5952 notation?
RFC 5952 defines a single recommended text form for IPv6: lowercase hex, no leading zeros, and :: used only for the longest run of zero groups, choosing the leftmost run on ties. This tool applies those rules so two equal addresses always print identically.
Does the tool support IPv4-mapped addresses and prefixes?
Yes. IPv4-mapped forms like ::ffff:192.0.2.128 are converted to hex groups, /prefix lengths up to /128 are preserved, zone IDs (e.g. fe80::1%eth0) are kept, and URL bracket notation like [2001:db8::1]:443 is accepted.
Is my data sent anywhere?
No. All parsing and formatting happens locally in your browser with plain JavaScript. Nothing is uploaded, so the tool works fully offline once the page is loaded.