What Is a Log Format?

Not all logs are created equal. Here are the heavy hitters:

Syslog (RFC 5424)

This granddaddy of log formats is the backbone of network device logging. Syslog is widely supported and relies on a standardized schema, but it doesn’t define the content. Translation? You still have to choose how to structure your log message. Despite its age, Syslog remains a go-to for routers, firewalls, and switches.

JSON-Based Logs

The cool kid of the logging world, JSON logs are highly readable and packed with context. Their nested structure makes it easy to add operational metadata while staying lightweight. JSON is a favorite for analytics-heavy tools and cloud platforms, thanks to its universal format.

Example:

```

{

"timestamp": "2024-01-15T08:45:12.345Z",

"severity": "ERROR",

"service": "web-application",

"message": "Unable to connect to database"

}

```

CSV and Tab-Delimited Logs

Simple and easy to generate, CSV (Comma-Separated Values) logs are great for short-term use or smaller systems. However, their lack of flexibility often makes them unsuitable for advanced security tools.

Key-Value Pair Logs

Straightforward and balanced, key-value pair logs are great for quick parsing and human readability. Example:

```

timestamp=2024-01-15T08:45:12Z severity=ERROR service=database message="Connection lost"

```

Apache and Nginx Combined Format

Web server logs often follow the Common Log Format (CLF) or its extended versions for tracking HTTP requests and responses. Despite being simple, they lack flexibility compared to options like JSON.