Best Free Online Developer Tools to Use in 2026
A practical, opinionated list of the best free online developer tools worth using in 2026, organized by category so you can find what you need fast.
Aug 08, 2026
IPv6 Calculator
Calculate IPv6 network addresses, prefix lengths, subnets, and expand/compress IPv6 notation
- Home
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- IPv6 Calculator
Expanded
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Compressed
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Network
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Prefix
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Total /64 Subnets
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Total Addresses
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First Address
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Last Address
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Global ID
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Subnet ID
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Interface ID
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Scope
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Binary Representation
What Is an IPv6 Calculator?
An IPv6 calculator is a network utility that helps network administrators, engineers, and students calculate and analyze IPv6 addresses and subnets. Unlike IPv4, IPv6 uses 128-bit addresses represented in hexadecimal notation, making manual calculations complex and error-prone. This tool automates the expansion and compression of IPv6 addresses, computes network prefixes, identifies subnet IDs, interface IDs, and global routing prefixes, and determines the total number of addresses and /64 subnets available within a given prefix.
Common use cases include planning IPv6 address allocations, verifying subnet boundaries during network design, teaching IPv6 addressing concepts, and troubleshooting connectivity issues. By providing immediate visual feedback for expanded, compressed, and binary representations, this calculator makes IPv6 subnetting accessible to both beginners and experienced professionals.
How to Use This Tool
- Enter an IPv6 address or prefix — Type a valid IPv6 address with an optional CIDR prefix length (e.g.,
2001:db8::/32) into the input field. - Click Calculate — Press the Calculate button or use an example button to quickly load a sample address.
- Review the results — Examine the expanded and compressed forms, network address, prefix length, total /64 subnets, total addresses, first and last addresses, global ID, subnet ID, and interface ID.
- Check the scope — The tool identifies the address scope (Global, Link-Local, Unique Local, Multicast, etc.) and shows the binary representation for educational purposes.
Frequently Asked Questions
What is the difference between IPv4 and IPv6 subnetting?
IPv6 subnetting works similarly to IPv4 but uses 128-bit addresses instead of 32-bit. IPv6 standard practice recommends using /64 subnets for most networks, providing 2^64 addresses per subnet. IPv6 subnetting focuses more on prefix allocation than address conservation, which was a primary concern in IPv4.
What does the prefix length mean?
The prefix length (e.g., /32, /48, /64) indicates the number of bits that define the network portion of the address. A /32 prefix typically identifies a provider allocation, /48 identifies a site, and /64 identifies a standard subnet. The remaining bits identify interfaces within that network.
What is the difference between global ID, subnet ID, and interface ID?
The global ID identifies the organization or site (typically bits after the provider prefix). The subnet ID identifies individual subnets within the site. The interface ID identifies the specific network interface, usually the last 64 bits of the address and often derived from the MAC address via EUI-64.
Why are there 2^64 addresses in a /64 subnet?
A /64 prefix leaves 64 bits for the interface identifier (128 - 64 = 64). With 64 bits, the total number of unique addresses is 2^64, which is approximately 18.4 quintillion addresses — enough for every device to have a unique global address.
Is my data sent to a server?
No. All calculations are performed locally in your browser. Your IPv6 addresses and prefixes never leave your device.
Last updated: 17 Aug 2026
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