Can I use
?

navigator.hardwareConcurrency

- LS

Returns the number of logical cores of the user's CPU. The value may be reduced to prevent device fingerprinting or because it exceeds the allowed number of simultaneous web workers.

Chrome

  1. 4 - 36: Not supported
  2. 37 - 105: Supported
  3. 106: Supported
  4. 107 - 109: Supported

Edge

  1. 12 - 14: Not supported
  2. 15 - 105: Supported
  3. 106: Supported

Safari

  1. 3.1 - 7.1: Not supported
  2. 8 - 10: Disabled by default
  3. 10.1 - 15.6: Supported
  4. 16.0: Supported
  5. 16.1 - TP: Supported

Firefox

  1. 2 - 47: Not supported
  2. 48 - 104: Supported
  3. 105: Supported
  4. 106 - 107: Supported

Opera

  1. 9 - 23: Not supported
  2. 24 - 90: Supported
  3. 91: Supported

IE

  1. 5.5 - 10: Not supported
  2. 11: Not supported

Chrome for Android

  1. 106: Supported

Safari on iOS

  1. 3.2 - 7.1: Not supported
  2. 8 - 10.2: Disabled by default
  3. 10.3 - 15.6: Supported
  4. 16.0: Supported
  5. 16.1: Supported

Samsung Internet

  1. 4 - 17.0: Supported
  2. 18.0: Supported

Opera Mini

  1. all: Not supported

Opera Mobile

  1. 10 - 12.1: Not supported
  2. 64: Supported

UC Browser for Android

  1. 13.4: Supported

Android Browser

  1. 2.1 - 4.4.4: Not supported
  2. 106: Supported

Firefox for Android

  1. 105: Supported

QQ Browser

  1. 13.1: Supported

Baidu Browser

  1. 13.18: Supported

KaiOS Browser

  1. 2.5: Supported
Resources:
WebKit implementation bug
MDN Web Docs - navigator.hardwareConcurrency
Original Proposal