zap

Overview

Zap is a Go logging library developed by Uber, specifically engineered for high-performance, structured logging in critical applications. It addresses common performance bottlenecks found in traditional logging solutions by minimizing memory allocations and CPU overhead, making it well-suited for production systems where every millisecond and byte counts. The library offers two distinct APIs: a "Sugared Logger" for convenience during development or in less performance-sensitive parts of an application, and a "Logger" API that prioritizes zero-allocation logging for maximum throughput and minimal garbage collection pressure. This dual approach allows developers to choose the appropriate level of performance and verbosity for different contexts within their codebase.

Structured logging, a core tenet of Zap, involves logging data in a machine-readable format, typically JSON. This approach significantly enhances the utility of logs for analysis, monitoring, and debugging by enabling automated parsing and querying of log entries. Rather than relying on human-readable strings that require complex regex patterns to extract information, structured logs provide key-value pairs that can be easily indexed and searched by log management systems. This capability is particularly valuable in microservices architectures or distributed systems, where correlating events across multiple services is crucial for effective troubleshooting.

Zap is designed for Go developers building applications that demand high throughput and low latency, such as API servers, real-time data processing pipelines, or high-volume background services. Its focus on performance means it can handle large volumes of log events without significantly impacting application performance. The library achieves this through techniques like pre-allocating buffers, avoiding reflection where possible, and providing efficient ways to add contextual fields to log entries. Developers can integrate Zap into their Go projects to gain detailed insights into application behavior, diagnose issues quickly, and maintain operational stability in demanding environments.

While Zap is highly optimized for performance, it also maintains a clear and intuitive API. The Sugared Logger provides a familiar interface similar to standard library loggers, allowing for quick adoption. For performance-critical sections, the explicit Logger API requires a slightly more verbose style but guarantees minimal overhead. This flexibility ensures that developers can achieve the desired balance between development speed and runtime efficiency. For example, a web server might use the Sugared Logger for request-level logging where context is added once per request, and the explicit Logger for hot paths within business logic that are executed many times per second.

The library's design also emphasizes extensibility, allowing developers to configure various output destinations (e.g., console, file, network) and custom encoders (e.g., JSON, console encoding). This modularity ensures that Zap can adapt to diverse logging infrastructure requirements, from simple local file logging to complex centralized log aggregation systems. Its robust feature set and performance characteristics have made it a popular choice within the Go ecosystem for applications requiring advanced logging capabilities.

Key features

• Structured Logging: Emits logs as machine-readable JSON by default, facilitating easier parsing, indexing, and analysis by log management systems. This improves debugging and monitoring workflows, especially in distributed systems, as detailed in the Zap structured logging documentation.
• High Performance: Optimized for minimal allocations and CPU overhead, making it suitable for high-throughput applications. It achieves this through techniques like zero-allocation logging and efficient field handling.
• Dual API: Offers both a convenient "Sugared Logger" for development and a "Logger" for zero-allocation, performance-critical logging. This allows developers to balance developer experience with runtime efficiency.
• Contextual Logging: Supports adding dynamic, typed fields to log entries, allowing for rich context to be associated with each log message. Fields can be added at the logger level or per log call.
• Configurable Output: Allows customization of log output destinations (e.g., standard output, files, network targets) and encoding formats (e.g., JSON, console).
• Sampling: Provides built-in sampling capabilities to reduce log volume during peak load, preventing log floods without losing critical error information.
• Level-Based Logging: Supports standard logging levels (Debug, Info, Warn, Error, DPanic, Panic, Fatal) with configurable thresholds, enabling fine-grained control over which messages are emitted.
• Extensibility: Designed with an extensible core, allowing for custom encoders, sinks, and hooks to integrate with various logging infrastructures and monitoring tools.

Pricing

Zap is an open-source Go library and is distributed free of charge under the MIT License. There are no licensing fees or commercial editions associated with its use. As of May 6, 2026, all features and ongoing development are publicly accessible on its official GitHub repository.

Common integrations

• Go Applications: Zap is a native Go library, integrating directly into any Go project for structured logging. Developers can consult the Zap Godoc documentation for API usage.
• Log Management Systems: Outputs logs in JSON format, which is directly consumable by popular log aggregation and analysis tools like Elasticsearch, Splunk, Datadog, and Sumo Logic. These systems can then parse, index, and visualize the structured log data.
• Monitoring and Alerting Tools: Integrated logs provide valuable data for monitoring application health and setting up alerts based on specific log patterns or error rates.
• Web Frameworks (e.g., Gin, Echo): Can be easily integrated into Go web frameworks to provide structured request logging, error logging, and contextual information for HTTP requests.
• Cloud Logging Services (e.g., Google Cloud Logging, AWS CloudWatch Logs): Zap's structured output is compatible with cloud-native logging services, allowing for centralized log collection and analysis in cloud environments.

Alternatives

• Logrus: A popular Go logging library offering a familiar API, customizable formatters, and various hooks for integration with external services. It provides structured logging but is generally less performant than Zap.
• Zerolog: Another high-performance, zero-allocation JSON logger for Go, often compared directly with Zap. Zerolog aims for extreme performance and ease of use, providing a concise API for structured logging.
• Standard library log: Go's built-in logging package provides basic logging functionality, suitable for simpler applications or initial development phases. It lacks structured logging capabilities and advanced performance optimizations.

Getting started

To begin using Zap in a Go project, first ensure you have a Go development environment set up. You can then install the Zap library using the go get command. The following example demonstrates how to set up a basic Zap logger, log an informational message with structured fields, and log an error.

First, install the package:

go get go.uber.org/zap

Next, create a Go file (e.g., main.go) and add the following code:

package main

import (
	"go.uber.org/zap"
)

func main() {
	// Create a new development logger. For production, use zap.NewProduction()
	// or zap.Config to customize.
	logger, _ := zap.NewDevelopment()
	defer logger.Sync() // Flushes buffer, if any

	// Use the sugared logger for convenience (less performant, but easier to use)
	sugar := logger.Sugar()
	sugar.Infow("Failed to fetch URL.",
		"url", "http://example.com",
		"attempt", 3,
		"error", "network timeout",
	)

	// Use the explicit logger for high-performance, zero-allocation logging
	logger.Info("User logged in",
		zap.String("user_id", "12345"),
		zap.Int("session_duration_seconds", 300),
	)

	// Log an error with context
	err := &MyCustomError{Code: 500, Message: "Database connection failed"}
	logger.Error("Application error occurred",
		zap.Error(err),
		zap.String("component", "database"),
		zap.Int("retry_count", 1),
	)
}

// MyCustomError represents a custom error type for demonstration.
type MyCustomError struct {
	Code    int
	Message string
}

func (e *MyCustomError) Error() string {
	return e.Message
}

Run the program:

go run main.go

The output will demonstrate structured log messages, typically in JSON format, written to the console. The Sugared Logger will produce more human-readable output by default in development mode, while the explicit Logger will output structured JSON. In a production environment, zap.NewProduction() would typically be used, which defaults to JSON output and higher performance settings.