zerolog (Go)
Zero-allocation JSON logger for Go with a fluent builder API. Zerolog achieves extremely low-latency logging by avoiding memory allocations in the hot path — logs are written directly to the underlying writer without intermediate allocations. Uses a chained API (log.Info().Str("key", "val").Msg("message")) for structured JSON output. Alternative to zap with a different ergonomic style.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Developers must avoid logging sensitive fields (passwords, tokens) — zerolog has no built-in redaction. Consider adding a custom hook to filter sensitive keys before writing to external sinks.
⚡ Reliability
Best When
You're building high-performance Go services where logging overhead matters and you want zero-allocation structured JSON output.
Avoid When
Your team prefers zap's API style or you need maximum compatibility with the standard library log package.
Use Cases
- • Add high-throughput structured JSON logging to Go microservices where logging overhead impacts performance
- • Build observability pipelines that emit structured logs consumable by ELK, Datadog, or Loki without parsing
- • Use context-aware logging by storing loggers in context.Context for request-scoped log fields
- • Log at multiple levels (Trace, Debug, Info, Warn, Error, Fatal) with level filtering for production tuning
- • Integrate with slog (Go 1.21+) via zerolog's slog bridge for standard library compatibility
Not For
- • Human-readable console logs in development — zerolog outputs JSON by default; add zerolog.ConsoleWriter for pretty output
- • Teams that prefer zap's sugar API — zerolog and zap are stylistically different; zap's SugaredLogger is more familiar coming from other languages
- • Applications using Go's standard log package everywhere — migration requires replacing log calls with zerolog's API
Interface
Authentication
Library with no auth requirement.
Pricing
Free and open source.
Agent Metadata
Known Gotchas
- ⚠ Zerolog's fluent chain MUST end with Msg(), Send(), or Msgf() — a chain without terminal call silently discards the log entry
- ⚠ log.Fatal() calls os.Exit(1) after logging — agents must understand this is not a panic and cannot be recovered from
- ⚠ Global logger (log.Logger) is a zerolog.Logger value, not a pointer — assigning it doesn't update the global; use log.Logger = newLogger
- ⚠ zerolog.SetGlobalLevel() affects ALL loggers including those passed in context — be careful with global level changes in libraries
- ⚠ JSON output by default means console logs are unreadable without zerolog.ConsoleWriter wrapper — always configure ConsoleWriter for local development
- ⚠ Zerolog disabled TRACE level by default at compile time via build tags — to enable trace logging, build with -tags trace flag; otherwise Trace() calls are no-ops
Alternatives
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Scores are editorial opinions as of 2026-03-06.