What is image compression?
Image compression changes how image data is stored so that the resulting file takes up less space. Two common approaches are lossless and lossy compression.
- Lossless compression: Reduces file size without discarding image information. The amount of reduction depends on the file and format.
- Lossy compression: Reduces file size by removing some image information. Stronger compression can make artifacts or loss of detail more noticeable.
How to compress an image
Follow these general steps to reduce an image's file size with an online compression tool.
- Choose your original image. Keep a copy of the original file in case you want to try different settings later.
- Open the image compressor. Visit the MARBPixel Image Compressor.
- Select a suitable quality setting. If a quality slider is available, begin with a moderate setting and adjust it based on your needs.
- Compress the image. Run the compression and wait for the output file to be generated.
- Compare the result. Check the new file size and inspect the image before using or sharing it.
Practical tip: Do not judge a compressed image only by its file size. Compare its appearance at the size people will actually view it.
Choose the right quality setting
For formats that use lossy compression, quality settings often involve a trade-off: a smaller file may show more compression artifacts, while a larger file may retain more visible detail.
There is no universal quality value that works for every image. A photograph, a product image, and a graphic containing small text may respond differently to the same setting.
- For website photographs: Try moderate compression and check that faces, textures, and fine details still look natural.
- For product images: Pay attention to edges, colors, and small details that customers may need to inspect.
- For graphics and text: Check for halos, blurring, or other artifacts around sharp edges.
Choose an appropriate image format
JPG
JPG is commonly used for photographs. It supports lossy compression and can produce relatively small files, although repeated lossy saving may reduce quality.
PNG
PNG supports lossless compression and transparency. It can be a good fit for graphics, screenshots, and images that need transparent backgrounds. Lossless compression may not substantially reduce every PNG file.
WebP
WebP supports both lossy and lossless compression, along with transparency. It can be an efficient option for many web images, but the best format depends on compatibility requirements and the image itself.
Learn more in our guide to JPG vs PNG vs WebP.
Compression and resizing are different
Compression reduces the amount of data needed to store an image. Resizing changes its pixel dimensions, such as reducing a 3000 × 2000 image to 1500 × 1000 pixels.
If an image is much larger than its intended display size, resizing it may reduce file size as well. However, resizing too far can remove detail needed for larger displays or future uses.
If you need specific dimensions, try the MARBPixel Image Resizer.
How to check image quality after compression
- Compare the compressed image with the original.
- View it at its intended display size.
- Zoom in on important details, text, and sharp edges.
- Check whether colors, gradients, or textures look noticeably different.
- Confirm that the final file meets the size and format requirements of your website or application.
Frequently asked questions
Can you compress an image without losing quality?
Sometimes. Lossless compression can reduce file size without discarding image information, but the amount of reduction depends on the file. Lossy compression can reduce file size further, but it may reduce visual quality.
What image quality setting should I use?
There is no single ideal setting for every image. Start with a moderate-to-high quality setting, compare the result with the original, and adjust it according to the image's intended use.
Does compressing an image reduce its dimensions?
Not necessarily. Compression changes how image data is stored. Resizing changes the image's pixel dimensions. You can use both techniques if you need to reduce file size substantially.
Which image formats can be compressed?
Common formats include JPG, PNG, and WebP. The results vary by format, image content, and compression method. Some formats and tools offer more control over lossy or lossless compression than others.
How can I tell whether an image is still good quality?
Compare the compressed image with the original at the size it will actually be displayed. Look closely at text, edges, gradients, faces, and other details that matter for your image.