How to Reduce Image Size on Mac

A photo can look fine on your Mac and still be too large to attach to an email. If you need to know how to reduce image size on Mac, make a smaller copy and check that copy before you send it. You can use a browser, or you can use Preview, the app that comes with the Mac. They are separate tools.

How to reduce image file size on Mac in a browser

The browser path is Quick Image Compress. It runs in Safari or Chrome on your Mac. The picture is handled in the browser. It is not sent to a server.

1. Open the image compressor and choose a JPG, PNG, or WebP. Each file can be up to 20 MB.
2. Leave Keep original format on unless you want a different type.
3. Start with Balanced, which is 75% quality. Open Advanced Settings for Low at 90%, High at 50%, or a target size.
4. Leave resizing off when the width and height should stay the same.
5. Click Compress Image and read the new size on the card.
6. Download the file. The name ends with “-compressed”. The original file in Finder is not replaced.

Use this path when you want WebP, a side-by-side comparison, or a goal such as 100 KB.

Resize or export in Preview

Preview is built into the Mac. It does not use this website. Choose it when you are already viewing the photo and you want a JPEG or PNG from Apple’s own menus.

1. Open the image in Preview.
2. Choose Tools, then Adjust Size.
3. Turn on Resample image when you want fewer pixels. Leave Scale proportionally on so the shape stays the same.
4. Choose pixels next to the width, then type a smaller number. The height should change with it.
5. Click OK.
6. Choose File, then Export.
7. Set Format to JPEG for a photo. Drag the Quality slider toward Least for a smaller file, or toward Best to keep more detail.
8. Save with a new name. Export writes a copy, so the first file can stay untouched.

Apple’s normal format list includes JPEG and PNG. WebP is not in that usual list. Hold Option while you open the Format menu only if you are looking for older extra formats. For WebP, come back to this site and choose WebP under Advanced Settings.

JPG, PNG, and WebP on a Mac

JPG is usually the simplest photo to shrink. Lower quality drops some detail, and the file often gets smaller. JPG cannot keep a clear background. Those areas become white.

PNG fits logos, screenshots, and flat graphics. At full quality it keeps its colors, so a PNG that is already compact may hardly change. A photograph saved as PNG is often heavier than the same photograph saved as JPG.

WebP can be a photo or a graphic, and on this site it can keep a clear background. Preview is the Mac path for a JPEG export. This site is the path when the file you need is WebP. The format comparison is in JPG vs PNG vs WebP.

See the real file size

In Finder, click the file you plan to send. Press Command and I together, or choose File, then Get Info. Read the Size line. That number belongs to the selected file. Select the export or the download, not the original, when the original is the one that was too big.

On this site, the card shows the compressed size directly. A label of 100.0 KB means 102,400 bytes, because 1 KB is 1,024 bytes.

Email, websites, and upload forms

An email often fails when one photo is several MB. Make a JPEG in Preview, or compress in the browser, then attach the new file. If Mail warns you, check Get Info on that attachment.

A page on a website should use a picture close to the size visitors will see. The steps for width and height are in how to reduce pixel size of an image.

A form that says 100 KB or 200 KB is asking about file size. Open compress an image toward 100KB or compress an image toward 200KB. After you compress, read Target Achieved or Target Not Achieved. Attach the file when the status matches the form.

Browser tool or Preview

When the copy is still too large

In Preview, export again with a lower JPEG quality, or set a smaller width while Resample image is on. Give each try a new name so you can compare them in Get Info.

On this site, change one setting and compress again. High is 50% quality. If the photo is still over the limit, turn on Enable Image Resizing, keep Maintain Aspect Ratio on, and type the width you need. A small PNG may barely move. A transparent PNG keeps all its colors here, so the quality slider does not shrink it.

Questions

Will Preview overwrite my only copy?

Export saves a new file when you choose a new name. Adjust Size changes the picture that is open, so export that result instead of replacing the only original.

Can I make a WebP file in Preview?

The usual Format menu offers JPEG and PNG, not WebP. Choose WebP on this site when that is the type you need.

Which tool should I open first?

Open Preview if you only need a JPEG and you are already in that app. Open the browser if you want a target file size, WebP, or a comparison slider.

Get Info shows a bigger size than the tool. Why?

The selected file may be the original. Click the exported or downloaded file and press Command and I again.

Both copies are still over the form’s limit. What next?

Lower the JPEG quality or the pixel width, then read the size of that new copy. A detailed photo can stay large until the picture itself is smaller.

Keep the first file until the new one is right

Use Preview for a Mac-only JPEG export. Use the browser when the result has to be WebP or has to meet a size you can read on the card. Either way, keep the file you started with until the smaller one is ready to send.