Can I use
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SPDY protocol

- UNOFF

Networking protocol for low-latency transport of content over the web. Superseded by HTTP version 2.

IE

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

Edge

  1. 12 - 93: Not supported
  2. 94: Not supported

Firefox

  1. 2 - 12: Not supported
  2. 13 - 50: Supported
  3. 51 - 92: Not supported
  4. 93: Not supported
  5. 94 - 95: Not supported

Chrome

  1. 4 - 50: Supported
  2. 51 - 94: Not supported
  3. 95: Not supported
  4. 96 - 98: Not supported

Safari

  1. 3.1 - 7.1: Not supported
  2. 8 - 12: Supported
  3. 12.1 - 14.1: Supported
  4. 15: Supported
  5. TP: Supported

Opera

  1. 9 - 12: Not supported
  2. 12.1 - 39: Supported
  3. 40 - 41: Not supported
  4. 42: Supported
  5. 43: Not supported
  6. 44: Supported
  7. 45 - 79: Not supported
  8. 80: Not supported

Safari on iOS

  1. 3.2 - 7.1: Not supported
  2. 8 - 12.1: Supported
  3. 12.2 - 14.8: Supported
  4. 15: Supported

Opera Mini

  1. all: Not supported

Android Browser

  1. 2.1 - 2.3: Not supported
  2. 3 - 4.4.4: Supported
  3. 94: Not supported

Opera Mobile

  1. 10 - 12: Not supported
  2. 12.1: Supported
  3. 64: Not supported

Chrome for Android

  1. 94: Not supported

Firefox for Android

  1. 92: Not supported

UC Browser for Android

  1. 12.12: Not supported

Samsung Internet

  1. 4: Supported
  2. 5 - 14.0: Not supported
  3. 15.0: Not supported

QQ Browser

  1. 10.4: Not supported

Baidu Browser

  1. 7.12: Support unknown

KaiOS Browser

  1. 2.5: Supported

See also support for HTTP2, successor of SPDY.

Chrome will be removing support in 2016 (in favor of HTTP2), other browsers likely to follow.

Resources:
SPDY whitepaper
Wikipedia