How image compression works, and how to get the smallest file with the least visible loss
Large images slow down websites, fill up inboxes, and get rejected by upload forms. Compression is the process of storing the same picture in fewer bytes. Done well, you can cut a photo to a fraction of its original size and still struggle to see the difference on a normal screen.
This tool offers four ready-made compression levels, optional resizing, and a choice of output format, all processed privately in your browser. Below you will find what compression actually does to your picture, how to pick the right level, and why some files shrink dramatically while others barely change.
Lossy and lossless compression, explained simply
Every image format compresses the picture in one of two ways. Lossless compression packs the data more tightly but can rebuild every pixel exactly, like putting a file in a zip archive. Lossy compression permanently throws away information, concentrating on detail that human vision is least sensitive to, such as tiny color differences in busy areas.
JPG and WebP are normally lossy. They let you trade a little quality for a much smaller file, which is why they dominate photography on the web. PNG is lossless, so it preserves every pixel but produces large files for photographs. This difference explains most of what you will see when you compress different types of images.
Choosing a compression level
Instead of asking you to guess a quality number, the tool groups the settings into four levels. Each one maps to a quality value used when the image is re-encoded.
| Level | Quality used | What to expect | Best for |
|---|---|---|---|
| Low | About 92% | Very close to the original with a modest size saving. | Photography portfolios and images you may edit again. |
| Recommended | About 75% | A strong balance: much smaller files with differences that are hard to notice. | Most websites, blogs, emails, and social posts. |
| High | About 50% | Clearly smaller files; fine texture and gradients can start to look rough. | Thumbnails, previews, and pages where speed matters most. |
| Extreme | About 28% | The smallest file; visible blockiness and color banding are likely. | Tiny uploads, drafts, and situations with a hard size limit. |
If you are not sure where to begin, choose Recommended and compare the preview. If the picture looks fine, try High to see whether the extra saving is worth it. If you see blocky patches around edges or smooth gradients turning into visible steps, go back one level.
Why some images shrink a lot and others barely change
Results vary because file size depends on the content as well as the settings. A photograph straight from a phone, packed with fine detail and saved at high quality, usually shrinks by well over half at the Recommended level. An image that has already been compressed by a messaging app or social network has less left to remove, so the saving is smaller.
Picture content matters too. Smooth areas such as a clear sky compress very efficiently, while grass, hair, fabric, and anything with fine noise needs far more data to look right. Screenshots and graphics with flat colors behave differently again, which brings us to the question of format.
Picking the right output format
The Output format control has four options: Keep, JPG, PNG, and WebP. Keep (the default) retains your original type where it can: PNG files stay PNG and WebP files stay WebP, while other files such as JPG and HEIC are saved as JPG.
- JPG. The safest option for photographs. Small, universally supported, and very predictable. Transparent areas are filled with white because JPG cannot store transparency.
- WebP. Usually the smallest result for both photos and graphics at similar visual quality, and it supports transparency. If the file is going onto a modern website, WebP is often the best choice. Check that the place you are uploading to accepts it.
- PNG. Lossless, so the compression level has no effect on the pixels. Use it only when you need exact colors or transparency, such as for a logo or screenshot. To make a PNG smaller, reduce its resolution or convert it to WebP or JPG.
Combine compression with a smaller resolution
Compression and resolution are two separate levers, and using both gives the biggest saving without hurting quality as much as pushing a single lever to the limit. The Image resolution option lets you keep the original size or enter a new width and height with the aspect ratio locked.
A practical recipe for web images: reduce the width to the largest size the image will ever be displayed at (often 1200 to 2000 pixels), then use the Recommended level. This usually beats using Extreme on a full-size photo, because you remove pixels nobody can see instead of damaging the ones they can.
If you need to land on a particular number rather than a general reduction, use Resize Image to KB. It searches for the highest quality that fits inside your limit, so you do not have to guess.
Where smaller images make a real difference
- Website speed. Images are often the heaviest part of a page. Smaller files load faster on slow mobile connections, improve the loading time of the main visual on the page, and use less of your visitors' data.
- Email and messaging. Many email services limit the total size of attachments. Compressing a handful of photos can be the difference between a message that sends and one that bounces.
- Online forms and portals. Job applications, insurance claims, and government websites commonly set an upper limit per file. Compress first, then upload.
- Storage and backups. A library of thousands of photos can shrink dramatically with sensible compression, saving device storage and cloud costs.
How to compress an image in four steps
- Add your image. Drag a JPG, PNG, WebP, HEIC, or GIF onto the upload area, or click to browse. Files up to 50 MB are supported.
- Choose a compression level. Start with Recommended. Optionally change the output format or set a smaller resolution.
- Compress and compare. The preview shows the original beside the result, with the new dimensions, file size, and how much smaller it is.
- Download. If the result looks right, save it. If not, change the level and compress again; your original is never modified.
Because processing happens on your device, nothing is uploaded and there is no waiting for a server. You can even keep the page open and compress several files in a row.
Privacy and quality notes
Your image never leaves your browser, and no account is required. Saving an image through the browser's canvas normally removes embedded metadata such as camera details and location tags, which is helpful when you share pictures publicly. One thing to be aware of is that animated GIFs are flattened to a single still frame, because the compressed result is a regular image, not an animation.
Frequently asked questions
How much smaller will my image get?
It depends on the picture, its original quality, and the level you choose. As a rough guide, a straight-from-camera photo often becomes 50 to 80 percent smaller at the Recommended level. Images that were already compressed will shrink less. The tool shows the exact percentage after each run.
Will compression make my picture blurry?
Compression does not blur an image so much as add small artifacts, such as slight blockiness or banding, when pushed hard. At Low and Recommended levels these are very hard to see. At High and Extreme they become more visible, especially around text and sharp edges.
What is the best format for compressed photos?
For photographs, WebP and JPG give the best size-to-quality results. JPG works everywhere, while WebP is usually a little smaller and supports transparency. Avoid PNG for photos unless you specifically need lossless quality, as the files will be much larger.
Why did my PNG not get smaller?
PNG is lossless and ignores the quality setting. To shrink a PNG, either lower its resolution or convert it to WebP or JPG. Be aware that JPG removes transparency, so choose WebP if you need to keep a transparent background.
Can I compress a file to an exact size, like 100 KB?
Compression levels are general presets and do not aim for a specific number. For a precise target, use the Resize Image to KB tool, which tests different quality settings until it finds the best-looking result that fits under your limit.
Can I compress many images at once?
This page handles one image at a time. To process a whole batch with the same settings and download everything as a single .zip, use the Resize Multiple Images tool.