IPv6 Address Compressor / Expander

Introduction:

Internet Protocol version 6 (IPv6) replaces the limited 32-bit address space of IPv4 with 128 bits, preventing exhaustion while supporting hierarchical routing, multicast, and autoconfiguration. Each address is written as eight 16-bit hexadecimal groups separated by colons, balancing human readability with immense numerical scale that complicates everyday inspection and error avoidance.

This client-side tool accepts a single IPv6 string, verifies structural correctness under RFC 5952 guidelines, expands suppressed zeros, recompresses the longest contiguous zero block, detects standard prefix categories, separates network and interface identifiers, and renders a 128-bit binary view, all through an in-browser reactive engine that never stores or transmits data.

During outage triage you can paste an address captured from packet traces, instantly verify validity, copy the uniformly compressed value into automation playbooks, or document loopback and link-local scopes in tickets. Typos spread rapidly through configuration management systems; always validate every quartet before committing device or firewall changes to shared repositories.

Technical Details:

IPv6 encodes host and network information in 128-bit unsigned integers expressed as hexadecimal quartets. Leading zeros within each quartet may be omitted, and a single contiguous run of zero quartets may be compressed to a double colon. These conventions drastically shorten everyday addresses but make textual variants non-unique, so reliable tooling must consistently expand, validate, recompress, and classify values to compare prefixes, generate reverse-DNS records, or derive interface identifiers reliably.

Core Process

1. Trim whitespace, convert to lowercase, and reject multiple :: tokens.
2. Split on ::; pad the missing quartets with zero strings until eight groups exist.
3. Left-pad individual quartets with zeros to four digits, producing the fully expanded canonical form.
4. Identify the longest consecutive zero sequence, replace it with ::, and remove redundant leading zeros to create the compressed form.
5. Evaluate the first quartet to label the address as loopback, link-local, unique-local, multicast, documentation, or global.
6. Translate each quartet from hexadecimal to binary, concatenating all 128 bits for bit-level inspection.

Address-Type Prefixes

The first quartet quickly signals routing behavior. For instance, multicast addresses beginning with ff never identify single hosts, whereas link-local addresses cannot traverse routers.

Key Variable

• ipv6 – raw user-supplied IPv6 string; accepts upper- or lowercase hexadecimal, optional shorthand.

Assumptions & Limitations

• Input must be a single IPv6 address, not a CIDR range.
• Parsing follows RFC 5952 textual representation rules.
• Tool ignores zone identifiers (for example, %eth0).
• Address-type classification relies solely on leading bits, not on registries.

Edge Cases & Error Sources

• Multiple :: tokens invalidate the address.
• More than eight quartets trigger rejection.
• Non-hexadecimal characters cause failure.
• Leading or trailing colons outside compression syntax are treated as errors.

Scientific Validity & References

The procedure conforms to RFC 4291 (IPv6 Addressing Architecture) and RFC 5952 (Preferred IPv6 Text Representation) and aligns with examples in IETF BCP 198.

Privacy & Compliance

Address strings are processed wholly within the browser; no personal data is transmitted, ensuring GDPR compliance.

Step-by-Step Guide:

Follow these steps to validate and normalize an IPv6 address.

1. Paste or type the address into the IPv6 address field.
2. Observe the immediate Valid/Invalid badge in the summary.
3. If valid, review the compressed and expanded forms and copy whichever version you need.
4. Select the Info, Groups, or Binary tab to inspect additional details.
5. Use the Copy buttons to transfer results into documentation or configuration files.

FAQ:

Glossary:

Quartet

Four hexadecimal digits representing 16 bits.

Compression

Technique of shortening the longest zero run to ::.

Network ID

Top 64 bits identifying the network segment.

Interface ID

Lower 64 bits uniquely identifying a host on the segment.

RFC 5952

IETF document describing preferred IPv6 text representation.