log-tail

Cross-platform tail -f replacement with regex filtering, JSON log parsing, level-based colorization, and multi-file watching. Zero dependencies.

Windows has no tail -f. PowerShell's Get-Content -Wait is clunky and doesn't filter. log-tail runs anywhere Node.js does.

Install

npm install -g log-tail

Or without installing:

npx log-tail server.log

Usage

log-tail server.log                        # tail -f equivalent
log-tail app.log error.log                 # Multiple files, labeled output
log-tail server.log --grep "ERROR|WARN"    # Filter lines
log-tail access.log --highlight "404"      # Highlight matches in red
log-tail app.json --json                   # Pretty-print JSON log lines
log-tail server.log -n 100 --no-follow     # Like `tail -100`, no follow
log-tail server.log --exclude "/health"    # Skip noisy lines

Auto-Colorization

Lines containing standard log levels are colored automatically:

| Pattern | Color | |---|---| | ERROR, FATAL, CRITICAL | red | | WARN, WARNING | yellow | | INFO, NOTICE | cyan | | DEBUG, TRACE | dim |

HTTP status codes (4xx, 5xx, etc.) are also highlighted.

Disable with --no-color.

JSON Log Mode

Given lines like:

{"level":"error","msg":"DB query timed out","timestamp":"2024-08-01T12:00:00Z","duration_ms":4012}

Run log-tail app.log --json:

2024-08-01T12:00:00Z ERROR DB query timed out  duration_ms=4012

Recognized fields:

• Message: message, msg, text
• Level: level, severity, lvl
• Timestamp: timestamp, time, ts

All other fields are shown as key=value extras.

Multi-File

When watching multiple files, each line is labeled with the filename in its own color:

server.log │ GET /api/users 200 12ms
worker.log │ Processing job #12345
server.log │ POST /api/login 401 4ms

Options

| Flag | Default | Description | |---|---|---| | -n, --lines <N> | 10 | Show last N lines before following | | --follow / --no-follow | follow | Keep watching for new lines | | --grep <pattern> | — | Only show lines matching regex | | --exclude <pattern> | — | Skip lines matching regex | | --highlight <pattern> | — | Highlight matches in bold red | | --interval <ms> | 250 | Poll interval | | --json | off | Pretty-print JSON log lines | | --no-color | off | Disable colorization |

License

MIT

Keywords

tail -f windows · tail follow · log viewer · follow logs · tail logs · log tail · live logs · json logs · cross-platform · zero dependencies

Built to solve, shared to help — Rushabh Shah 🛠️✨

One of 40+ zero-dependency developer CLI tools — no node_modules, ever.