Zap
Blazing-fast structured logging library for Go, created by Uber. Provides two loggers — zap.NewProduction() for JSON structured logs with field typing, and zap.NewExample() / zap.NewDevelopment() for development. Fields are typed (zap.String, zap.Int, zap.Duration) avoiding reflection overhead. 10-100x faster than standard Go log package for high-throughput services.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
MIT licensed. Uber-maintained with strong security practices. Avoid logging sensitive data — typed fields make it explicit what's being logged.
⚡ Reliability
Best When
You're building a high-throughput Go service (API gateway, event processor) where logging overhead is measurable and structured JSON logging is required.
Avoid When
You need a simple logging setup for low-throughput services — zerolog or stdlib log is simpler. Zap's typed field API adds verbosity.
Use Cases
- • High-performance structured JSON logging in Go agent services where logging overhead must be minimal
- • Add typed field logging to Go agent services: logger.Info('request', zap.String('method', 'GET'), zap.Duration('latency', d))
- • Replace Go's standard log package in production agent services with structured, leveled logging
- • Integrate with OpenTelemetry for trace context injection into Go agent service logs
- • Build custom Zap encoders and cores for specialized log output formats in agent services
Not For
- • Applications where log performance is not critical — zerolog or even stdlib log work fine for low-throughput services
- • Simple scripts — stdlib log or fmt.Println is sufficient; Zap's setup is heavy for simple use cases
- • Applications requiring dynamic log level changes at runtime without restart — use zerolog with atomic level
Interface
Authentication
Local library — no authentication required. MIT licensed.
Pricing
MIT licensed. Zero cost.
Agent Metadata
Known Gotchas
- ⚠ Two loggers: zap.Logger (typed fields, fastest) and zap.SugaredLogger (printf-style, slightly slower) — use Sugar() to convert: slogger := logger.Sugar(); slogger.Infow('msg', 'key', val)
- ⚠ Fields are typed: zap.String('key', val), zap.Int('count', n), zap.Error(err) — mixing up types causes compile errors (good!) but requires verbose field declarations
- ⚠ Logger must be 'built' from Config: zap.NewProduction() or zap.NewDevelopment() — not a constructor; production config outputs JSON, development outputs console format
- ⚠ Named loggers: logger.Named('component') adds a name field to all log entries — useful for identifying which subsystem logged a message
- ⚠ Core composition: zapcore.NewTee(core1, core2) for multiple outputs simultaneously — e.g., JSON to file AND console — without creating separate loggers
- ⚠ Defer logger.Sync() at app start to flush buffered log entries before process exit: defer logger.Sync() // flushes buffered log entries
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Zap.
Scores are editorial opinions as of 2026-03-06.