On June 30, Apple released OS X 10.10.4 update to fix the widespread networking issues that was plugged since 10.10. Apple replaced the home grown Discoveryd process with good old industry tested mDNSResponder. The troubled Discoveryd was introduced in OS X 10.10 back in October 2014.

The OS X Yosemite 10.10.4 update improves the stability, compatibility, and security of your Mac, and is recommended for all users.
This update:
- Improves networking reliability
- Improves Migration Assistant reliability
- Addresses an issue that prevented certain external monitors from functioning properly
- Improves the reliability of upgrading iPhoto and Aperture libraries to Photos
- Improves reliability when syncing photos and videos to iCloud Photo Library
- Addresses an issue that caused Photos to quit unexpectedly after importing some Leica DNG files
- Resolves an issue that could delay outgoing email messages in Mail
- Fixes an issue where a website could prevent the user from navigating away by presenting repeated JavaScript alerts in Safari

This 10.10.4 update primarily focuses on stability improvements and bug fixing.