Regex for Logs: Filter INFO, WARN, ERROR, Dates, and IDs

Filter log levels

Alternation can accept several levels at the beginning of a line.

Regex: ^(INFO|WARN|ERROR)\s+

Add a date

Combine the level group with a structural ISO-like date.

Regex: ^(INFO|WARN|ERROR)\s+\d{4}-\d{2}-\d{2}

Capture useful fields

Capturing groups can separate the level, date, and identifier for later processing. Named groups are useful when your engine supports them and they improve readability.

Avoid brittle patterns

If your log format changes frequently, a very strict Regex may break often. Structured JSON logs and observability tools can be better for production parsing.

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.

Keep learning