Window.devicePixelRatio

- WD

Read-only property that returns the ratio of the (vertical) size of one physical pixel on the current display device to the size of one CSS pixel.

IE

  1. 5.5 - 10
  2. 11

Edge

  1. 12 - 81
  2. 83

Firefox

  1. 2 - 17
  2. 18 - 75
  3. 76
  4. 77 - 78

Chrome

  1. 4 - 81
  2. 83
  3. 84 - 86

Safari

  1. 3.1 - 13
  2. 13.1
  3. TP

Opera

  1. 9 - 11.5
  2. 11.6 - 67
  3. 68

iOS Safari

  1. 3.2 - 13.3
  2. 13.4

Opera Mini

  1. all

Android Browser

  1. 2.1 - 4.4.4
  2. 81

Blackberry Browser

  1. 7
  2. 10

Opera Mobile

  1. 10 - 11.5
  2. 12 - 12.1
  3. 46

Chrome for Android

  1. 81

Firefox for Android

  1. 68

IE Mobile

  1. 10
  2. 11

UC Browser for Android

  1. 12.12

Samsung Internet

  1. 4 - 10.1
  2. 11.1

QQ Browser

  1. 10.4

Baidu Browser

  1. 7.12

KaiOS Browser

  1. 2.5

As the page is zoomed in the number of device pixels that one CSS pixel covers increases, and therefore the value of devicePixelRatio will also increase.

Resources:
MDN Web Docs - devicePixelRatio