Manatee

How to convert a JPEG to PNG on a Mac

· 6 min read

Converting a JPEG to PNG rewraps a photo in a lossless format, which is useful when an app or workflow requires PNG, or when you want a copy that will not lose more quality as you edit it. It will not recover detail the JPEG already discarded, and for photographs the PNG is usually larger, not smaller. The fastest way on a Mac is to drop the file on a converter, choose PNG, and save; Preview can do it too.

What JPEG and PNG actually are

JPEG is a lossy format built for photographs. It compresses hard by throwing away detail the eye tends not to miss, which is why a JPEG photo is small, and why every extra save degrades it a little more. It has no transparency and it is not designed to survive repeated editing.

PNG is lossless. It stores every pixel exactly, so nothing is discarded when you save, and it supports transparency. That precision makes it the right format for screenshots, logos, diagrams, and any image with sharp text or hard edges. The cost is size: for a continuous-tone photograph, a PNG can be several times larger than the JPEG it came from, because lossless compression cannot squeeze a photo the way JPEG does.

The key thing to hold onto is that converting from JPEG to PNG changes the container and the compression method, not the picture. Whatever the JPEG already lost stays lost.

Why convert JPEG to PNG, and what it cannot do

There are good reasons to make the switch:

  • A program, template, or upload form accepts only PNG.
  • You are about to edit the image and want to avoid stacking more JPEG compression on top with each save. PNG is a safe working format because it never degrades.
  • You need to place the image on a canvas that can hold transparency, or you plan to cut out a background in an editor and want a format that can store the result.

It is just as important to know what the conversion will not do. It will not sharpen or clean up a blurry or blocky JPEG; the artifacts baked into the JPEG are copied faithfully into the PNG. It will not add transparency by itself; a JPEG has a solid background, so the PNG starts with that same solid background until you edit it. And it will not make the file smaller; for a photo, expect the PNG to be noticeably larger.

Convert a JPEG to PNG on a Mac

Manatee handles the conversion in seconds and can take a batch of files at once:

  1. Open Manatee and choose Convert, or drag the JPEG onto its menu bar icon.
  2. Pick PNG as the target.
  3. Drop in the file, or a folder of them. Each appears in the job list with progress.
  4. The new PNG is written next to the original. The JPEG is untouched, so nothing is lost from your source.

It all runs on your Mac, with no upload and no account, and because Manatee always writes a new copy, your original JPEG stays exactly as it was.

The built-in option is Preview:

  1. Open the JPEG in Preview.
  2. Choose File, then Export.
  3. Set the Format to PNG.
  4. Click Save.

Preview is fine for a single image. The trade-off is that it converts one file at a time, so a large batch is tedious. QuickLook, the space-bar preview, will show the JPEG but cannot convert it.

Size and quality: setting expectations

The most common surprise is that the PNG comes out bigger than the JPEG, sometimes much bigger. That is not a mistake. JPEG achieved its small size by discarding data; PNG refuses to discard anything, so it needs more room to store the same photograph exactly as the JPEG now looks, artifacts and all. For a screenshot or a flat graphic the sizes can be closer, because those images have the large areas of uniform color that PNG compresses well.

On quality, the honest summary is that the PNG will look identical to the JPEG and no better. Converting is a way to freeze an image at its current quality and stop further loss, which is genuinely valuable in an editing pipeline, but it is not a repair or an upgrade. If your real problem is a low-quality JPEG, no format change will fix it.

This is also why the direction of conversion matters. Going JPEG to PNG once, before you start editing, is sensible. Bouncing an image back and forth between the two formats gains you nothing and wastes space; each JPEG step still degrades the picture even though each PNG step does not.

Questions

Will converting to PNG improve the image quality?

No. PNG stores the JPEG exactly as it already looks, including any compression artifacts. It stops future quality loss but cannot recover detail the JPEG threw away.

Why is my PNG larger than the JPEG?

Because PNG is lossless. JPEG got small by discarding data; PNG keeps everything, so a photograph needs more space. That is expected, and it is the price of not losing any more quality.

Does converting to PNG give the image a transparent background?

Not on its own. The JPEG has a solid background, and the PNG keeps it. PNG can hold transparency, but you would have to remove the background in an image editor after converting.

When is it actually worth converting JPEG to PNG?

When a tool requires PNG, or when you are about to edit and re-save an image several times and want to avoid compounding JPEG compression. For simply sending or storing a photo, the JPEG is usually the better choice.