slog-pretty

Pretty-printer for Go's slog JSON logs — inspired by pino-pretty.

• Zero dependencies — standard library only
• Two ways to use: CLI pipe or slog.Handler
• Color-coded log levels, source locations, nested object expansion
• Respects NO_COLOR and auto-detects TTY

Install

CLI

# Homebrew
brew install mickamy/tap/spretty

# Go
go install github.com/mickamy/slog-pretty/cmd/spretty@latest

Build from source

git clone https://github.com/mickamy/slog-pretty.git
cd slog-pretty
make install

Docker

ARG SPRETTY_VERSION=0.1.0
ADD https://github.com/mickamy/slog-pretty/releases/download/v${SPRETTY_VERSION}/slog-pretty_${SPRETTY_VERSION}_linux_${TARGETARCH}.tar.gz /tmp/spretty.tar.gz
RUN tar -xzf /tmp/spretty.tar.gz -C /usr/local/bin spretty && rm /tmp/spretty.tar.gz

Usage with air or go run:

air | spretty
go run ./cmd/server | spretty

Library

go get github.com/mickamy/slog-pretty

Quick Start

As a CLI pipe

Pipe any JSON log output through spretty:

go run ./your-app | spretty

Output:

10:15:30.123 INFO  server started
  port=8080
  host=localhost
10:15:31.456 ERROR connection failed (main.connect /app/main.go:42)
  host=db.local
  retry=3

Non-JSON lines are passed through unchanged.

As a slog.Handler

package main

import (
	"log/slog"
	"os"

	spretty "github.com/mickamy/slog-pretty"
)

func main() {
	logger := slog.New(spretty.NewHandler(os.Stdout, &spretty.HandlerOptions{
		Level:     slog.LevelDebug,
		AddSource: true,
	}))

	logger.Info("server started", "port", 8080)
	logger.With("request_id", "abc-123").Error("timeout", "host", "db.local")
}

CLI Flags

Flag	Default	Description
--time-format	15:04:05.000	Go time format
--no-color	false	Disable colored output
--ignore		Comma-separated keys to omit
--version, -V		Show version and exit

Colors are automatically disabled when stdout is not a TTY or when NO_COLOR is set.

Handler Options

NewHandler accepts HandlerOptions and formatting Options:

spretty.NewHandler(w, hopts, opts...)

HandlerOptions

Field	Type	Default	Description
Level	slog.Leveler	slog.LevelInfo	Minimum log level
AddSource	bool	false	Include source file and line

Formatting Options

Function	Description
WithTimeFormat(format)	Set time format (Go layout string)
WithNoColor()	Disable ANSI colors
WithIgnoreKeys(keys...)	Omit specified keys from output

Output Format

<time> <level> <message> (<source>)
  <key>=<value>
  <key>=
    <nested_key>=<value>

• Time: gray
• Level: DEBUG=blue, INFO=green, WARN=yellow, ERROR=red
• Message: bold
• Source: dim
• Keys: cyan
• Nested objects are indented; arrays are inline JSON

License

MIT