Dev
Log Format Generator
Unstructured log lines that mix timestamps, levels, and messages in a bespoke format are unindexable. This tool generates a structured log format specification and a realistic sample line so you have a concrete template to copy into your logger or web-server config. Pick the format — JSON (structured), logfmt, nginx access log, or Apache combined — and enter your service name. The JSON output specifies one JSON object per line (NDJSON) with fields `ts`, `level`, `service`, `msg`, `trace_id`, `duration_ms`, and `status`, plus a sample. The logfmt output produces the same fields as `key=value` pairs. The nginx output shows the `log_format` directive for the `http` block. The Apache output shows the `LogFormat` directive and a sample combined line. Keep field names identical across services — consistency makes cross-service log queries reliable.
How to use
- Choose your options above
- Click Generate
- Copy your result
Detailed instructions
- Pick the log format you want.
- Enter your service name.
- Click Generate to see the spec and a sample line.
- Copy it into your logger or web-server config.
Use Cases
- •Standardising application logs as structured JSON
- •Configuring an nginx or Apache access log format
- •Choosing between JSON and logfmt for readability
- •Including a trace id and duration in every log line
- •Giving a parser a known sample line to test against
Tips
- →Prefer structured logs so tools can index and search them.
- →Always include a trace id to correlate logs across services.
- →Log durations in milliseconds to spot slow requests.
- →Keep the field set identical across services for clean queries.
FAQ
should I use JSON or logfmt
JSON is the better choice when a log pipeline like Datadog, Loki, or Elasticsearch ingests your logs — every tool parses it natively. Logfmt is more readable when tailing a terminal because `key=value` pairs scan faster for human eyes. Both are structured and superior to unformatted text.
why include a trace_id in the log format
A trace ID ties together every log line from a single request across services. Without it, correlating the logs for one failing checkout means guessing which lines belong together. With it, you filter on one ID and see the entire request path.
where do the nginx and Apache format directives go
The nginx `log_format` directive goes in the `http {}` block and is referenced by `access_log` in a `server` block. The Apache `LogFormat` line defines a nickname used in a `CustomLog` directive. The sample line confirms the layout for testing your log parser.
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