To convert a PNG and keep its transparent areas, save it in another format that supports transparency, such as TIFF or HEIC, and confirm the exported file still looks transparent in a suitable viewer. On macOS, Preview offers these formats through File > Export. JPEG cannot retain transparency, so exporting to JPEG will replace transparent pixels with a solid background. Apple’s Preview guide lists its export formats; MDN’s image format guide explains PNG’s alpha transparency and JPEG’s lack of an alpha channel.

Choose a format that can preserve transparency

Transparency is image data: PNG can store varying transparency for pixels, commonly called alpha transparency. A format that does not support that data cannot carry it through a conversion. For a Mac conversion in Preview, TIFF and HEIC are among the formats Apple lists alongside PNG; JPEG is also listed, but it does not support transparency. Do not use JPEG when the see-through background is part of the result you need. Apple Support · MDN

A file extension alone does not establish that an image contains transparency: an opaque PNG stays opaque when converted, and a checkerboard shown by an editor may be only its display for transparent areas. The goal is to preserve transparency that exists in the source, not to create it during conversion.

Convert one PNG with Preview

  1. In Finder, locate the PNG and open it in Preview. If another app opens it by default, Control-click the file, choose Open With, then select Preview.
  2. In Preview, choose File > Export.
  3. In the Format menu, choose a transparency-capable destination such as TIFF or HEIC. Apple documents these options, and notes that holding Option while opening the menu can reveal specialized or older formats if the format you need is not shown. The visible list can depend on macOS and the available export options.
  4. Enter a distinct filename or choose another folder so the original PNG remains available. Click Save.
  5. Reopen the exported file and inspect a transparent edge or area. If possible, place or view it against contrasting backgrounds in an application that displays transparency. A white-looking background in Preview or another viewer does not by itself prove the image was flattened; display behavior varies by app.

Apple documents the Export menu, supported formats, saving under a new name or location, and batch export from files selected in one Preview window’s sidebar. It does not document a macOS Preview checkbox named “preserve transparency” in this workflow, so do not rely on an invented toggle. Apple: Convert image file types using Preview on Mac

Convert multiple files in one Preview window

For a small group of images, open them in one Preview window, select the files in the sidebar, then use File > Export and choose the output format. Apple documents this batch workflow. Before converting a large set, try one representative PNG first: verify that the chosen format works in the app or service where you plan to use it, and inspect the exported file for the transparency you need. Apple Support

When transparency disappears

If the converted image has a solid background, first check the destination format. A JPEG export cannot preserve alpha transparency; the image must be composited against a color when converted to that format. If transparency is essential, export to a suitable format instead and retain a copy of the source PNG. MDN

If you do not see the destination format in Preview, hold Option while clicking the Format menu to check Apple’s documented additional formats. If the file still cannot be saved in the needed format, Preview may not offer a compatible export path for that particular task or version. Use an image editor or converter that explicitly documents alpha-channel export for the destination, then verify the result in a transparency-aware app. Apple documents Shortcuts as capable of format conversion, but its general guide does not specify that a particular conversion preserves alpha; treat it as an option to investigate, not a guarantee. Apple: Shortcuts transform actions

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