Why do exported photos from my Mac have different sizes or formats?

They may be different because an export is not always a copy of the imported file. In Photos on Mac, the standard Export command lets you choose an output type and, for supported types, options such as JPEG quality, image size, and color profile. Those choices can change the exported file’s format, dimensions, or size. Apple describes JPEG as suitable for smaller files and sharing, HEIC as efficient for Apple devices, and TIFF and PNG as lossless options. [S1]

A separate command, “Export Unmodified Original,” exports the imported file in its original format. If you choose different formats or settings in separate exports, differences are expected; the exact file size cannot be predicted from the format name alone. [S1]

Photos distinguishes the edited presentation from the original. Its editing tools include cropping, rotation, and exposure or color adjustments. In Edit view, you can compare the edited item with its original; “Image > Revert to Original” removes edits and restores the original image. [S2]

To investigate, compare the same photo in Edit view, then note whether you used standard Export or Export Unmodified Original. The export guide documents format and size controls, but does not establish a universal file-size change caused by edits. So treat edits as one possible difference to inspect, not a guaranteed explanation for a larger or smaller file. [S1][S2]

For a shareable copy, use standard Export and choose the output type and available settings that suit the recipient or destination. JPEG is described as suitable for sharing and smaller files; HEIC is described as efficient for Apple devices. If a recipient or service requires a particular type, check that requirement before exporting rather than assuming it accepts every format. [S1]

For the imported file in its original format, choose “Export Unmodified Original.” This is distinct from exporting the edited presentation. If you need to retain an edited version too, export it separately with the standard command; label the files clearly so you can tell which is which. [S1][S2]

Use one photo and change one choice at a time. For example, assume you are comparing an edited photo with its imported original; this is an illustrative setup, not a claim about what your Mac will produce:

1. Export the edited presentation using standard Export. Record the selected format and any available quality, image-size, or color-profile choices.
2. Export the same item using “Export Unmodified Original.” Record its file type and dimensions.
3. Compare the resulting files’ format, dimensions, and file size. If you make another standard export, change only one setting so you can see which choices differ.

Keep in mind that the export controls explain which choices are available, not what exact file size any setting will produce. [S1]