logpretty

Pretty-print JSON logs in the terminal. Supports pino, winston, and bunyan formats out of the box.

If you use structured logging, your raw logs look like this:

{"level":30,"time":1700000000000,"pid":12345,"hostname":"server1","msg":"User signed in","userId":"u_8fk2","latency":42}
{"level":50,"time":1700000001000,"pid":12345,"hostname":"server1","msg":"Database connection failed","error":"ECONNREFUSED","retries":3}
{"level":40,"time":1700000002000,"pid":12345,"hostname":"server1","msg":"Rate limit approaching","current":980,"max":1000}

Pipe them through logpretty and get this:

2023-11-14 22:13:20.000 INFO  User signed in
    userId: u_8fk2
    latency: 42
2023-11-14 22:13:21.000 ERROR Database connection failed
    error: ECONNREFUSED
    retries: 3
2023-11-14 22:13:22.000 WARN  Rate limit approaching
    current: 980
    max: 1000

Timestamps in gray, levels color-coded (ERROR = red, WARN = yellow, INFO = green, DEBUG = blue), messages in bold white, and extra fields neatly indented below.

Installation

# npm
npm install -g logpretty-cli

# yarn
yarn global add logpretty-cli

# pnpm
pnpm add -g logpretty-cli

Usage

Pipe any JSON log stream through logpretty:

# From a log file
cat app.log | logpretty

# From a running process
node server.js 2>&1 | logpretty

# Docker logs
docker logs -f myapp | logpretty

# PM2 logs
pm2 logs --raw | logpretty

Non-JSON lines pass through unchanged, so mixed output works fine.

Options

--no-color          Disable colored output
--level-key <key>   Custom field name for log level  (default: "level")
--msg-key <key>     Custom field name for message    (default: "msg", "message")
--time-key <key>    Custom field name for timestamp  (default: "time", "timestamp", "@timestamp")
-h, --help          Show help

Supported Log Formats

pino

{"level":30,"time":1700000000000,"pid":42,"hostname":"app","msg":"Request completed","responseTime":12}

winston (JSON transport)

{"level":"info","message":"Server started","timestamp":"2023-11-14T22:13:20.000Z","port":3000}

bunyan

{"name":"myapp","hostname":"server","pid":1234,"level":30,"msg":"Listening","time":"2023-11-14T22:13:20.000Z","v":0,"port":8080}

Custom formats

Use the --level-key, --msg-key, and --time-key flags for any format:

cat custom.log | logpretty --level-key severity --msg-key text --time-key ts

How It Works

1. Reads stdin line by line
2. Attempts to parse each line as JSON
3. If valid JSON object: extracts timestamp, level, and message fields, then pretty-prints with ANSI colors. Extra fields are displayed indented below the main line.
4. If not JSON: prints the line unchanged

Zero Dependencies

This tool has no dependencies. It uses only Node.js built-in modules (readline). Install it and it just works.

License

MIT -- Tate Lyman