How to Compress Images Without Visibly Losing Quality

What compression actually does

Image compression reduces file size in two main ways. Lossless methods rearrange the data more efficiently and can be reversed exactly. Lossy methods, like most JPEG compression, throw away detail the eye is least likely to notice, which saves much more space but cannot be undone.

For web and email use, lossy compression at a sensible level is usually the right trade-off. The key is stopping before the damage becomes visible.

Resize first

The single most effective step is making the image the right size. A photo straight from a modern phone can be thousands of pixels wide, yet it may be displayed in a column a few hundred pixels across. Serving the full-size file wastes bandwidth and storage.

Decide the largest size at which the image will be displayed, allow for sharper high-density screens, and resize to that. Only then apply compression.

Choose the right format

Photographs generally belong in JPEG. Screenshots, logos and graphics with sharp edges and text usually look cleaner and are sometimes smaller as PNG. Transparent backgrounds require PNG or another format that supports transparency.

Newer formats can reduce size further, but older software, forms and email clients may not accept them. When the destination is unknown, JPEG and PNG are the safe choices.

• Photos: JPEG.
• Logos, line art, screenshots: PNG.
• Transparency needed: PNG.
• Strict upload forms: JPEG.

Compress step by step

Using the Image Compressor:

• Add your image from your device.
• Choose a quality level or target size.
• Compare the preview with the original.
• Download the compressed copy and keep the original.

How to compare before and after

Open both versions side by side and zoom to 100 percent. Look at areas with smooth gradients, such as skies and skin, which show blocky artefacts first, and at sharp edges around text, which can look fuzzy or surrounded by speckles.

If you can see damage at normal viewing size, increase the quality setting a notch. If you cannot see any difference, you may be able to compress further.

Targets for forms and uploads

Some uploads demand an exact limit rather than a quality level. For those, use a tool built around a target size such as Resize Image to 100 KB or 50 KB. It will adjust quality automatically until the file fits.

If you are putting images into a document, a combined file can be made with Image to PDF after compressing the individual pages.

Compressing for websites and social media

Websites benefit most from careful image handling, because images are often the heaviest part of a page. Resize to the maximum display width, compress, and give each image a descriptive file name and alt text. Large hero images deserve extra attention, since visitors see them first and a slow load is noticeable.

Social platforms re-compress what you upload, so starting with a clean, correctly sized file helps. Uploading a huge image does not guarantee a sharper result; it often just means the platform's own compression is applied to a larger source. Check the recommended dimensions for each platform, which change from time to time.

For email, a handful of images at moderate size is usually fine, but a dozen full-resolution photos can push a message over the attachment limit. Compress first, or share a link to an album instead. Keep the originals safe so you can always produce a different size later.

Habits that keep quality high

Always compress from the original, never from an already compressed copy, because repeated lossy compression stacks damage. Keep a folder of untouched originals, and save web copies under different names. Avoid screenshots of screenshots, which add compression twice.

When in doubt, aim for the smallest file that you cannot tell apart from the original on your actual screen. That standard is more useful than any specific number.