Change an image's file format on Mac

You’ve got an image in one format and you need it in another. Maybe a HEIC that needs to be JPG, a PNG that needs to be WebP, or a TIFF that needs to be anything smaller. The mechanics are the same regardless of the formats involved — only the tradeoffs change.

The native way: Preview

The universal answer for one file at a time:

1. Open the image in Preview.
2. File → Export.
3. Pick the target format from the Format dropdown.
4. If JPEG, set quality.
5. Save.

Preview supports exporting to: JPEG, JPEG-2000, OpenEXR, PDF, PNG, TIFF, and HEIC. It reads even more (GIF, BMP, WebP on Ventura+, etc.).

The native way: sips

sips is faster for batches and supports the same formats:

sips -s format <target> input.ext --out output.ext

Examples:

sips -s format jpeg photo.png --out photo.jpg
sips -s format png photo.jpg --out photo.png
sips -s format heic photo.png --out photo.heic
sips -s format tiff photo.jpg --out photo.tiff

Set JPEG quality with -s formatOptions 85 before the input.

The faster way

Drag any image (or folder) into Melt, pick the target format from the dropdown, set quality if relevant, click Compress. Handles batches, lets you also resize or strip metadata in the same pass. Download Melt.

Change format in Melt

1. Open Melt.
2. Drag your image(s) in.
3. Pick the target format.
4. Adjust quality if it's a lossy format (JPEG, WebP, AVIF).
5. Click Compress.

Pick the right target

• JPEG — photos, broadest compatibility, smaller files, lossy.
• PNG — graphics, screenshots, transparency, lossless, larger files.
• HEIC — Apple ecosystem, very small files, lossy, limited compatibility outside Apple.
• WebP — modern web, ~30% smaller than JPEG, broad browser support.
• AVIF — newest, smallest, but app support still patchy outside browsers.
• TIFF — print, archival, multi-page, big.

If the destination is the web, pick WebP or JPEG. If it’s another Apple device, HEIC. If it’s general sharing, JPEG. If it’s print, TIFF.

When format conversion isn’t lossless

Going from any lossy format (JPEG, HEIC, WebP, AVIF) to anything else doesn’t recover the data that’s already been lost. Going from a lossless format (PNG, TIFF, BMP) to a lossy one loses data. Going lossless-to-lossless (PNG ↔ TIFF) is bit-perfect.

What you lose, what you keep

Lossy-to-lossy conversion is doubly lossy. Lossless-to-lossy throws away data permanently. Lossless-to-lossless preserves everything. EXIF metadata is preserved by all the tools above unless you ask otherwise (Melt strips by default). Keep originals when going lossy; the conversions can be regenerated, the originals cannot.