Can I use
?

:placeholder-shown CSS pseudo-class

- WD

Input elements can sometimes show placeholder text as a hint to the user on what to type in. See, for example, the placeholder attribute in HTML5. The :placeholder-shown pseudo-class matches an input element that is showing such placeholder text.

Chrome

  1. ❌ 4 - 46: Not supported
  2. ✅ 47 - 141: Supported
  3. ✅ 142: Supported
  4. ✅ 143 - 145: Supported

Edge

  1. ❌ 12 - 18: Not supported
  2. ✅ 79 - 141: Supported
  3. ✅ 142: Supported

Safari

  1. ❌ 3.1 - 8: Not supported
  2. ✅ 9 - 26.0: Supported
  3. ✅ 26.1: Supported
  4. ✅ 26.2 - TP: Supported

Firefox

  1. ❌ 2 - 3.6: Not supported
  2. ◐ 4 - 50: Partial support
  3. ✅ 51 - 143: Supported
  4. ✅ 144: Supported
  5. ✅ 145 - 147: Supported

Opera

  1. ❌ 9 - 33: Not supported
  2. ✅ 34 - 121: Supported
  3. ✅ 122: Supported

IE

  1. ❌ 5.5 - 9: Not supported
  2. ◐ 10: Partial support
  3. ◐ 11: Partial support

Chrome for Android

  1. ✅ 142: Supported

Safari on iOS

  1. ❌ 3.2 - 8.4: Not supported
  2. ✅ 9 - 18.6: Supported
  3. ✅ 26.0: Supported
  4. ✅ 26.1: Supported

Samsung Internet

  1. ❌ 4: Not supported
  2. ✅ 5 - 28: Supported
  3. ✅ 29: Supported

Opera Mini

  1. ❌ all: Not supported

Opera Mobile

  1. ❌ 10 - 12.1: Not supported
  2. ✅ 80: Supported

UC Browser for Android

  1. ✅ 15.5: Supported

Android Browser

  1. ❌ 2.1 - 4.4.4: Not supported
  2. ✅ 142: Supported

Firefox for Android

  1. ✅ 144: Supported

QQ Browser

  1. ✅ 14.9: Supported

Baidu Browser

  1. ✅ 13.52: Supported

KaiOS Browser

  1. ◐ 2.5: Partial support
  2. ✅ 3: Supported

For support of styling the actual placeholder text itself, see CSS ::placeholder

Resources:
Firefox bug
WebKit commit