How to Compress an Image on Mac (4 Easy Ways)

Way 1: Compress an image with Preview

• Step 1: Open the picture. Double click the image. It opens in Preview, the built in viewer on every Mac.
• Step 2: Open Export. Click File in the menu bar, then choose Export.
• Step 3: Choose JPEG. Set the Format to JPEG. The Quality slider appears below it.
• Step 4: Lower the quality. Drag the Quality slider to the left. Preview shows the estimated file size under the slider.
• Step 5: Save. Click Save. The original stays untouched and you get a smaller copy.

Way 2: Resize the picture in Preview

Reducing the number of pixels is the most effective way to make a file smaller. A photo of 4000 pixels wide is far bigger than most forms or websites need.

• Step 1: Open Adjust Size. In Preview, click Tools in the menu bar, then Adjust Size.
• Step 2: Set a smaller width. Change the unit to pixels and enter a smaller width, for example 1000. Keep Scale proportionally ticked so the height follows.
• Step 3: Save. Click OK, then File and Export to save a copy with the lower quality setting if needed.

Way 3: Use a free online image compressor

An online compressor is the fastest way when you need a specific size, because it shows the file size of the result before you download it.

• Step 1: Add your pictures. Open the Image Compressor in Safari or Chrome and drag your pictures into the box.
• Step 2: Set a width and a quality. Start with a maximum width of about 1000 pixels and a quality of about 75 percent.
• Step 3: Check the size. Look at the size shown for each picture and lower the quality a little if it is still too large.
• Step 4: Download. Download the compressed pictures. Everything happens in your browser, so your photos are not uploaded to a server.

Way 4: Convert HEIC photos to JPG

iPhone photos are often saved as HEIC. Many websites do not accept this format, so converting to JPG helps with both compatibility and size.

• Step 1: Open the HEIC picture in Preview. Double click the file.
• Step 2: Export as JPEG. Choose File, then Export, set the format to JPEG and adjust the quality.

Which method should you choose?

• One or two pictures. Preview is quick and needs nothing extra.
• A target size such as 100 KB. Use the online compressor, because it shows the size as you change the settings.
• Many pictures at once. Use the online compressor, which handles several images in one go.
• iPhone HEIC files. Export them as JPG first, then compress.

Tips for a clean result

• Resize first, compress second. A smaller width keeps the picture sharper at the same file size.
• Use JPG for photos. PNG files are much larger. Use PNG only for logos and transparent backgrounds.
• Start from the original. Compressing a compressed picture again lowers the quality further.
• Keep your originals. Store the original photos somewhere safe, because compression cannot be undone.

Common problems and fixes

• The Quality slider is missing. The Quality slider only appears for JPEG and HEIC. Choose JPEG in the Format menu.
• The file is still too large. Lower the width first, then the quality. Fewer pixels save more space.
• The picture looks blurry. The quality or the width is too low. Raise one of them a little.
• My PNG does not get small. PNG is lossless. Export it as JPEG if it has no transparency.

Compress your image now

Add your picture in the Image Compressor, set a width and a quality and watch the size until it fits your limit. It is free, adds no watermark and needs no signup.

Frequently asked questions