Quite a few channels broadcast programmes in high definition, with the balance of their schedules up-converted from standard definition.  

Look for the HD icon in the Freeview TV Guide.

The HD channels you get depend on how you watch Freeview.

If you watch Freeview via UHF aerial (the Terrestrial service), you can watch in HD on the following channels:

TVNZ 1, TVNZ 2, Three, Whakaata Māori, DUKE, Sky Open, Rush, Eden, Trackside 1 and Trackside 2.

If you watch Freeview via satellite, you can watch in HD on the following channels:

TVNZ 1, TVNZ 2, Three, Whakaata Māori, DUKE and Sky Open.

If you watch on the Freeview Streaming TV app, many channels are in HD or near-HD (1080p or 720p), so you can expect great picture quality, though the specific setup and bandwidth of your home broadband or WIFI connection can also affect the quality of the stream you ultimately get.

Tip! There's less bandwidth or space for free-to-air TV over satellite, so if you don't want to stream the channels and prefer to tune in through a TV antenna, you will get more HD channels if you tune in with a UHF aerial. To do that, first check to make sure you have UHF coverage (check your coverage here).