Why your photos are HEIC in the first place
Since iOS 11, iPhones have saved photos as HEIC because it stores roughly the same picture in about half the space of a JPEG. macOS reads it natively, so nothing looks broken on your Mac. The friction shows up everywhere else: older Windows machines, upload forms, print shops, and plenty of older software still expect a JPEG.
Option 1 — Finder Quick Actions
Select the photos in Finder, right-click, and choose Quick Actions → Convert Image. Pick JPEG or PNG, choose an image size, and macOS writes new files next to the originals. It is built in, handles many files at once, and is the fastest route for a one-off batch.
What you give up is control. You choose Small, Medium, Large, or Actual Size rather than a real quality setting or exact pixel dimensions, and your only destinations are JPEG, PNG, and HEIF.
Option 2 — Preview
Open the photo in Preview, then File → Export, set Format to JPEG, and drag the Quality slider. Preview shows the resulting file size as you drag, which Quick Actions will not. For several photos, select them in Finder, open them together in one Preview window, select every thumbnail in the sidebar, and use File → Export Selected Images.
Preview gives you genuine quality control and a few more output formats. The batch flow is fiddly, and it will not resize on the way out.
Option 3 — a dedicated converter
Worth it once you are converting regularly, need an exact pixel size, care what happens to metadata, or want to see the encoded result before it is written. SnappyEdit converts a whole batch in one pass with a real quality setting, resizes during export, and previews the actual encoded output. It stages every file and only commits it after the encode validates, so your originals are never modified.
A word on online converters
Every free “HEIC to JPG” website works by uploading your photos to someone else’s server. For a landscape shot that may not matter. For photos of your family, your documents, or your passport, you are handing a copy to a company whose retention policy you have not read. Everything above happens without a single byte leaving your Mac.
JPEG or PNG?
Choose JPEG for photographs headed to people, print shops, or upload forms: universally supported and small. Choose PNG for screenshots, logos, and anything with sharp edges, text, or transparency. Avoid PNG for camera photos — it produces much larger files with no visible benefit.
If the file you are wrestling with came from a website rather than a phone, see converting WebP to PNG on a Mac.