How to Compress an Image With Squoosh and Check the Quality

A photo that looks fine on your screen can be a pain to upload or send when its file is huge. Squoosh gives you a visual comparison and an estimated output size so you can make a smaller copy without guessing blind.

Quick answer: Open Squoosh, choose an image, select an output format on the right, and adjust the quality if that format offers it. Compare the image and file sizes, download the right-hand result, and open the new file to check it. Keep your original.

We tested this with a disposable, original illustration in a desktop browser. The example below shows one image and one set of settings, not a guaranteed reduction for your files.

1. Open an image and choose a format

1. Go to squoosh.app and use the image picker, or drag a file onto the page. You can also try one of the provided examples first.
2. Wait for the comparison view. The left side starts with the original image; the right side offers an output format and compression settings.
3. Choose an output format that the destination accepts. For a photo where JPEG is accepted and transparency isn’t needed, MozJPEG is one option. If the destination requires PNG or a transparent background, don’t assume a JPEG will work: JPEG does not preserve transparency.

Squoosh is a web app from Google Chrome Labs. Its privacy statement says image compression happens locally and the image is not sent to a server. It also says the app uses Google Analytics to collect visitor data and before-and-after image sizes; local processing does not mean zero analytics.

2. Compare quality with file size

With MozJPEG selected, adjust Quality and wait for the output size to update. Lower quality can reduce file size but can also introduce visible artifacts. Inspect fine text, edges and gradients at a useful zoom level. Drag the center divider to compare the original and compressed versions.

In our test, a 50.2 kB PNG illustration produced a 13.5 kB MozJPEG at quality 75. Changing quality to 60 produced a 10.4 kB estimate. A photo, a different format, or different settings can produce a very different result. Don’t pick a number just because it worked on this example.

If the recipient specifies pixel dimensions as well as a file-size limit, those are separate requirements. Squoosh has a Resize control; changing dimensions removes or alters pixels, so keep your full-size original. We did not test resizing for this guide.

3. Download and verify the copy

1. When the right-hand result looks acceptable, select its blue download button.
2. Find the downloaded file and open it. Check the picture at its intended display size, especially text, fine detail and edges.
3. Check the file type, dimensions and file size against the destination’s requirements. If the result looks rough or is still too big, return to the original and try another setting.

We downloaded the sample result and verified that it was a 1,200 × 800 JPEG. We did not test every format, browser, phone or image type. A smaller file is useful only if it still looks good enough for its job.

Need a Mac-only option? Our Preview conversion and resizing guide covers the built-in app. Squoosh’s side-by-side preview and output-size comparison are useful when you want to judge a compression tradeoff before downloading.

How we checked: We opened Squoosh, loaded a purpose-made sample, adjusted MozJPEG quality, compared the reported sizes, and downloaded and inspected the output file. Squoosh interface by Google Chrome Labs; screenshot captured by TRT.