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go get -u go.uber.org/zap

Note that zap only supports the two most recent minor versions of Go.

In contexts where performance is nice, but not critical, use theSugaredLogger. It's 4-10x faster than other structured loggingpackages and includes both structured andprintf-style APIs.

logger,_:=zap.NewProduction()deferlogger.Sync()// flushes buffer, if anysugar:=logger.Sugar()sugar.Infow("failed to fetch URL",// Structured context as loosely typed key-value pairs."url",url,"attempt",3,"backoff",time.Second,)sugar.Infof("Failed to fetch URL: %s",url)

When performance and type safety are critical, use theLogger. It's evenfaster than theSugaredLogger and allocates far less, but it only supportsstructured logging.

logger,_:=zap.NewProduction()deferlogger.Sync()logger.Info("failed to fetch URL",// Structured context as strongly typed Field values.zap.String("url",url),zap.Int("attempt",3),zap.Duration("backoff",time.Second),)

See thedocumentation andFAQ for more details.

For applications that log in the hot path, reflection-based serialization andstring formatting are prohibitively expensive — they're CPU-intensiveand make many small allocations. Put differently, usingencoding/json andfmt.Fprintf to log tons ofinterface{}s makes your application slow.

Zap takes a different approach. It includes a reflection-free, zero-allocationJSON encoder, and the baseLogger strives to avoid serialization overheadand allocations wherever possible. By building the high-levelSugaredLoggeron that foundation, zap lets userschoose when they need to count everyallocation and when they'd prefer a more familiar, loosely typed API.

As measured by its ownbenchmarking suite, not only is zap more performantthan comparable structured logging packages — it's also faster than thestandard library. Like all benchmarks, take these with a grain of salt.¹

Log a message and 10 fields:

Log a message with a logger that already has 10 fields of context:

Log a static string, without any context orprintf-style templating:

All APIs are finalized, and no breaking changes will be made in the 1.x seriesof releases. Users of semver-aware dependency management systems should pinzap to^1.

We encourage and support an active, healthy community of contributors —including you! Details are in thecontribution guide andthecode of conduct. The zap maintainers keep an eye onissues and pull requests, but you can also report any negative conduct tooss-conduct@uber.com. That email list is a private, safe space; even the zapmaintainers don't have access, so don't hesitate to hold us to a highstandard.

Released under theMIT License.

¹ In particular, keep in mind that we may bebenchmarking against slightly older versions of other packages. Versions arepinned in thebenchmarks/go.mod file.↩