Before you start: test every pattern with examples that should match and examples that should fail.
Basic IPv4 structure
This pattern verifies four groups of one to three digits. It is useful for teaching and extracting candidates, but it accepts out-of-range values.
Regex: ^(?:\d{1,3}\.){3}\d{1,3}$The range problem
999.999.999.999 has the right shape but is not a valid IPv4 address. Encoding 0-255 directly in Regex is possible, but much less readable.
When to use a parser or library
For production validation, networking utilities from your language are often clearer and more reliable, especially once IPv6 is involved.
Match the solution to the task
Extracting IP-looking values from logs may only need the structural pattern. Validating a network configuration needs semantic validation.
Next step: test it for real
Use the Playground to experiment with the pattern, then practice in the game with feedback on false positives and false negatives.