Image Compressor

How to compress images

1. Drop one or several images onto the box, or click Choose images. Anything your browser identifies as an image is accepted; other files are ignored.
2. Pick the output Format (JPG or WebP), the Quality slider (30 to 95, starting at 75) and the Max side (Original, 3840, 2560, 1920, 1280 or 800 pixels, starting at 1920).
3. Each file gets a row showing its name and original size. When processing finishes, the row shows the saving as a percentage and a download button with the new size.
4. Changing a setting re-runs the compression on every image in the list, always starting from your original files, so you can experiment without the quality degrading further each time.

Each result downloads under its original name with a new extension, for example holiday.png becomes holiday.jpg. The original file on your device is never changed.

What the tool does to each image

The browser draws the image onto a hidden canvas and then saves that canvas in the chosen format. Two things reduce the file size:

• Resizing. If the longer side of the image is larger than the Max side, both sides are scaled down by the same factor, so the proportions are kept. A 4000 × 3000 photo with the 1920 limit becomes 1920 × 1440, which is only about 23% of the original pixel count. Images that are already smaller are not enlarged.
• Lossy encoding. JPG and WebP store an approximation of the picture. A lower quality value throws away more fine detail and gives a smaller file.

Resizing is usually the bigger lever. A modern phone photo is often far larger than any screen needs, and cutting the pixel count by three-quarters can shrink the file dramatically without any visible change on a normal display. Lowering quality from 75 to 50 saves further, but artefacts such as blockiness around edges appear sooner.

Choosing settings for a purpose

• Photo for email or a form upload with a size limit: JPG, quality 70 to 75, Max side 1280 or 1920. If the upload still fails, drop to 1280 first, then lower quality.
• Images on a web page: WebP is often smaller than JPG at a similar visual quality, and all current mainstream browsers display it. Use it if you control where the images appear; use JPG if the file will be sent to other people or into software that may not read WebP.
• Thumbnails and previews: 800 pixels, quality 60 to 70.
• Screenshots with text: keep quality at 85 or above and check the result at full size, since lossy compression makes small text look smudged near the letters.

Things that change or disappear

• Transparency becomes white in JPG. JPG has no transparent areas, so the tool paints a white background first. Choose WebP if you need to keep see-through areas from a PNG logo.
• Extra data is removed. Because the image is redrawn, details stored alongside the picture, such as camera model or GPS location in a photo, are not copied into the new file. That is often welcome before sharing, but do not use this tool to make archival copies.
• Animated images lose their animation. Only a single still frame is drawn onto the canvas.
• PNG is an input only. There is no PNG output option, so flat graphics with sharp edges and few colours may look worse after conversion or even grow in size.

Why the saving can be negative

The percentage beside the download button shows how much smaller the new file is. If the result is larger, it is shown as an increase in red. This happens when the original was already compressed harder than your current settings, for example a web-optimized JPG re-saved at quality 90, or a screenshot PNG converted to JPG. Lower the quality, reduce the Max side, or simply keep the original. Re-saving a JPG as a JPG always adds a little extra loss, so avoid repeating it on the same picture.

Tips and limits

• Very large images or many files at once need memory on your device. If a phone struggles, process a few images at a time.
• Files are handled one by one in your own browser, and nothing is sent anywhere, so it works even with confidential documents.
• The slider range stops at 95, not 100, because the last few steps add large amounts of data for no visible gain.
• There is no batch download as an archive; use each row's download button.
• Settings are not remembered between visits.

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