What is the difference between IPv4 and IPv6?

IPv4 (Internet Protocol version 4):
Address Size:

IPv4 has 32-bit addresses.
It provides about 4.3 billion unique addresses (2^32).
Address Format:

IPv4 addresses are written in decimal and displayed as four numbers separated by dots.
Example: 192.168.1.1
Header Size:

The size of the header in IPv4 is 20-60 bytes.
Network Configuration:

Network configuration is done manually or via DHCP (Dynamic Host Configuration Protocol).
Security:

IPv4 does not have built-in security features, IPSec has to be added.
IPv6 (Internet Protocol version 6):
Address Size:

IPv6 has 128-bit addresses.
It provides about 3.4 x 10^38 unique addresses (2^128), which is much more than IPv4.
Address Format:

IPv6 addresses are written in hexadecimal and displayed as eight groups separated by colons.
Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Header Size:

The header size in IPv6 is 40 bytes.
Network Configuration:

IPv6 features auto-configuration, making it easy to setup. Security:

IPv6 has built-in IPSec support, which provides better security.

Other important differences:

Exhaustion:

The IPv4 address space is almost exhausted, while the IPv6 address space is very vast and will not be exhausted for a long time.

Routing:

Routing is more efficient and faster due to the simple header structure of IPv6.

Compatibility:

IPv4 and IPv6 are not directly compatible with each other. They require transition mechanisms to work together.