Why does an image look blurry after compressing it?

What changes when you compress an image

Lossy compression of JPG and WebP reduces the file by discarding some of the visual information. At moderate levels, many changes go unnoticed. When the quality drops too low, soft edges, spots around text, blocks in gradients, and loss of texture in hair, leaves, or fabric appear.

Compression is not always the only cause. A photo that is 600 pixels wide will look blurry if a page enlarges it to 1200 pixels, even if it was saved at high quality. That's why it's important to separate two questions: did the file lose detail when encoding or does it simply not have enough pixels for the display size?

How to identify the cause

1. Opens the original and compressed file at the same zoom level.
2. Compare areas with text, diagonal edges, soft shadows, and fine details.
3. Check the pixel dimensions of both files.
4. View the result at its final size, not just as a thumbnail.
5. If the original is also blurry, compression cannot recover detail that was never present.

Signs of too strong compression

• Square blocks: are usually noticeable on ceilings, walls and gradients.
• Halos: appear around letters, dark objects, or lines with high contrast.
• Pasted textures: hair, grass and fabrics lose separation.
• Colors in bands: a smooth gradient turns into visible stripes.

If you see these defects, open the original again in the image compressor and gradually increase the quality. Avoid recompressing the previous output, because each new lossy export can accumulate damage.

Recommended quality based on content

There is no universal percentage. A natural photograph tolerates more compression than a screenshot with small print. As a starting point, use a medium-high quality for photos and a high quality for interfaces, diagrams, or images that contain text. Then compare the weight and appearance in the preview.

If a screenshot must retain perfectly defined edges, try PNG. For stills, JPG or WebP usually offer a more reasonable balance. The guide of JPG, PNG and WebP explains when each format is appropriate.

Resolution may also be the problem

Downsizing permanently removes pixels. This is useful when the original image is much larger than the space in which it will be displayed, but can cause lack of sharpness if the result is below the necessary size. An image that will be 800 pixels wide should retain at least that width; On high density screens it may be useful to prepare a larger version.

Avoid enlarging a small image with CSS, a slideshow, or an editor. The browser can interpolate pixels to fill the space, but it doesn't invent the lost detail.

How to fix a blurry image

1. Recover the original version or the higher resolution copy.
2. Choose the format according to the content: JPG or WebP for photos; PNG for transparency, fine text, or simple graphics.
3. Compress at a softer level and keep the dimensions if they are already suitable.
4. Review the result at 100% and also within the final design.
5. Download only when the weight savings justifies the visual difference.

Frequently Asked Questions

Can I sharpen an already compressed image?

A filter can increase edge contrast, but it does not recover discarded information. The most reliable solution is to go back to the original and export again with better settings.

Why does the thumbnail look good and the large image doesn't?

By reducing it, defects take up less space and are difficult to distinguish. Zoom in on important details and check the actual post size.

Is smaller file always better?

No. The goal is to achieve a weight appropriate for the end use without introducing noticeable defects. Saving a few kilobytes is not worth losing readability.