---
tag: m0123
title: Fan Tachometers
brief: Report fan speeds from tachometers
author: thinkyhead

group: control

codes: [ M123 ]

examples:
- pre: Report current fan speeds
  code: M123

- pre: Report fan speeds every 5 seconds
  code: M123 S5

---

If your machine has fans with tachometers this command will report their current speed readings in RPM. Marlin can also auto-report the fan speeds at regular intervals, as set by `M123 S`.
