The internet relies on two protocol versions for device addressing: IPv4 and IPv6. Understanding their differences matters for network planning, security, and choosing the right proxy infrastructure. This guide covers how both protocols work, where they differ, and what the transition means in practice.

What is IPv4?

IPv4 (Internet Protocol version 4) is the fourth version of the Internet Protocol and has been the foundation of internet communication since 1981. It uses 32-bit addresses written in dotted-decimal notation (e.g., 192.168.1.1), providing roughly 4.3 billion unique addresses.

That number seemed vast in the 1980s but is now exhausted. The last top-level IPv4 address blocks were allocated by IANA in 2011. Today, IPv4 addresses are managed through reuse, secondary markets, and Network Address Translation (NAT) — a technique where multiple devices on a private network share a single public IPv4 address.

What is IPv6?

IPv6 (Internet Protocol version 6) uses 128-bit addresses written in hexadecimal colon notation (e.g., 2001:0db8:85a3::8a2e:0370:7334). This provides approximately 340 undecillion (3.4 × 10³⁸) unique addresses — effectively unlimited for any foreseeable demand.

IPv6 was designed to solve IPv4’s address exhaustion while also improving security, routing efficiency, and device auto-configuration. It eliminates the need for NAT, giving every device a globally routable address.

IPv6 address types

IPv6 defines several address categories, each serving a different purpose:

Unicast: Identifies a single network interface. A packet sent to a unicast address is delivered to exactly one device. This is the most common type, equivalent to a standard IPv4 address.
Multicast: Identifies a group of interfaces. A packet sent to a multicast address is delivered to all members of the group simultaneously. IPv6 uses multicast as a replacement for IPv4’s broadcast (which does not exist in IPv6).
Anycast: Assigned to multiple interfaces, but a packet is delivered to the nearest one (by routing distance). Used for load balancing and redundancy — for example, DNS root servers use anycast addressing.
Link-local: Automatically assigned to every IPv6 interface (prefix fe80::/10). Used for communication within a single network segment — neighbor discovery, router solicitation, and other local operations. Link-local addresses are not routable beyond the local link.

Key differences: IPv4 vs IPv6

Feature	IPv4	IPv6
Address length	32 bits	128 bits
Address format	Dotted decimal (192.168.1.1)	Hexadecimal colon (2001:db8::1)
Address space	~4.3 billion	~3.4 × 10³⁸
Header size	20–60 bytes (variable)	40 bytes (fixed)
NAT required	Yes (in most deployments)	No
IPSec	Optional	Built-in
Auto-configuration	DHCP required	SLAAC (stateless)
Multicast	Optional	Native
Fragmentation	Routers and sender	Sender only

Security

IPv4 was designed in an era of trusted academic networks where the nodes on the network were known to each other. Security mechanisms were added later as optional extensions rather than built into the protocol itself. IPSec (Internet Protocol Security) exists for IPv4, providing authentication and encryption at the network layer, but it is rarely deployed because it requires explicit configuration on both endpoints.

IPv6 includes IPSec as a mandatory part of the protocol specification. Every IPv6 implementation must support AH (Authentication Header) for packet integrity verification and ESP (Encapsulating Security Payload) for encryption. In practice, this means any two IPv6-capable devices can negotiate encrypted communication without application-layer changes — though whether IPSec is actually activated depends on the operating system configuration and network policy.

Additionally, IPv6’s elimination of NAT means end-to-end connectivity is restored. While NAT in IPv4 provided an incidental layer of obscurity (devices behind NAT are not directly addressable), this was never a designed security feature. IPv6 replaces this with proper firewall rules and IPSec, which provide explicit, configurable security rather than relying on architectural side effects.

Performance and routing

IPv6 uses a simplified, fixed-size header (40 bytes) compared to IPv4’s variable-length header (20–60 bytes). This allows routers to process IPv6 packets more efficiently. The fixed size means routers do not need to parse variable-length option fields on every packet — they know exactly where the payload begins.

IPv6 also eliminates router-level fragmentation — only the sending device can fragment packets. This reduces router processing overhead and improves network reliability. In IPv4, any router along the path could fragment a packet, adding complexity and potential for packet loss during reassembly.

A feature unique to IPv6 is flow labels — a 20-bit field in the header that allows routers to identify packets belonging to the same traffic flow. This enables quality-of-service (QoS) handling without deep packet inspection. Routers can prioritize real-time traffic (video, VoIP) at the network layer without examining the payload, which is more efficient than application-layer QoS mechanisms.

Native multicast support in IPv6 enables efficient one-to-many data transmission without the workarounds required in IPv4. IPv6 also supports privacy extensions (RFC 4941), which generate temporary, randomized interface identifiers for outbound connections. This prevents long-term tracking of devices by their IPv6 address — a privacy feature with no IPv4 equivalent.

IPv6 adoption: where are we?

As of 2025, Google reports that approximately 45% of traffic to its services arrives over IPv6. Adoption varies significantly by country — India, the US, Germany, and France lead, while many regions in Africa and Asia still rely primarily on IPv4.

Most networks today run dual-stack configurations, where devices support both IPv4 and IPv6 simultaneously. This allows a gradual transition without breaking compatibility with IPv4-only services.

Full IPv4 replacement is unlikely in the near term. Legacy systems, enterprise infrastructure, and the sheer scale of deployed IPv4 equipment ensure both protocols will coexist for years.

IPv4 vs IPv6 for proxy users

For residential proxy users, IPv4 remains the practical default. The vast majority of websites and services are fully reachable over IPv4, and residential ISPs overwhelmingly assign IPv4 addresses to households.

IPv6 residential proxies are growing in availability but are less universally accepted — some target websites and APIs don’t yet handle IPv6 traffic correctly. If your workflow requires maximum compatibility, IPv4 is the safer choice.

LocalProxies supports both IPv4 and IPv6 residential IPs, with IPv4 as the default across all plans. Check our locations page for current coverage, or see the FAQ for protocol-specific questions.

Frequently asked questions

Is IPv6 faster than IPv4?

In theory, yes — IPv6’s simplified header and elimination of NAT can reduce latency. In practice, the difference is negligible for most applications. Routing paths and network quality matter more than protocol version.

Will IPv4 stop working?

No. IPv4 and IPv6 will coexist for the foreseeable future via dual-stack deployments. There is no planned “shutdown date” for IPv4.

Can IPv4 and IPv6 work together?

Yes. Dual-stack configurations allow devices to use both protocols simultaneously. Transition mechanisms like NAT64 and DNS64 also enable IPv6-only devices to reach IPv4 services.

Do residential proxies support IPv6?

Some providers do, including LocalProxies. However, IPv4 is more widely supported across target websites. We recommend IPv4 as the default unless your specific use case requires IPv6. Start a free trial to test both.

IPv4 and IPv6 in proxy-dependent workflows

Understanding the protocol version matters when setting up proxy-based workflows for specific industries:

Ad verification: Most ad networks serve content over IPv4. IPv4 residential proxies ensure you see the same ads as real users in each target market.
Travel fare aggregation: Airline and hotel booking systems are predominantly IPv4. Using IPv4 proxies from the booking origin country gives you accurate localized pricing.
SEO monitoring: Search engines serve results over both protocols, but IPv4 remains the safer choice for consistent, comparable SERP data across regions.
Brand protection: Marketplace monitoring typically requires IPv4 connections to access product listings as a normal consumer would.

LocalProxies defaults to IPv4 across all plans to maximize compatibility with target websites. IPv6 is available on request for specific use cases.

Transition mechanisms: how IPv4 and IPv6 coexist

The transition from IPv4 to IPv6 is not a hard cutover. Several mechanisms allow both protocols to work together during the migration period:

Dual-stack: Devices run both IPv4 and IPv6 simultaneously, choosing the appropriate protocol for each connection. This is the most common transition approach used by ISPs today.
NAT64 / DNS64: Allows IPv6-only networks to communicate with IPv4 servers. A NAT64 gateway translates between the two protocols, and DNS64 synthesizes IPv6 addresses for IPv4-only destinations.
6to4 and Teredo tunneling: Encapsulate IPv6 packets within IPv4 for transport across IPv4-only networks. These are less common now that native IPv6 deployment has grown, but remain in use for legacy network configurations.

For most residential proxy users, dual-stack is transparent — your proxy provider handles the protocol selection. If you want to understand more about how proxy protocols work at the network level, see our guide on SOCKS proxy servers.

Choosing between IPv4 and IPv6 proxies

When selecting a proxy plan, consider these factors:

Target website compatibility: If your target sites are IPv4-only (most are), use IPv4 proxies. Testing with IPv6 against an IPv4-only target will result in connection failures.
Pool size: IPv4 residential proxy pools are significantly larger than IPv6 pools at most providers, including LocalProxies. More IPs means better rotation and lower block rates.
Cost: IPv4 and IPv6 proxies are typically priced the same, but IPv4’s larger pool provides more value for rotation-heavy workflows.
Future-proofing: If your target ecosystem is moving toward IPv6 (common in mobile-first markets), testing with IPv6 proxies now can surface compatibility issues early.

Check our locations page for current IPv4 pool depth across all 195+ countries and territories, or visit the FAQ for protocol-specific questions.