K-magpie › Kmagpie Tools › Compress Images
Compress Images
Compress many images at once — set a target file size and the quality adjusts itself to hit it. Files never leave your browser: no upload, no sign-up, no watermark.
Around 80 is the sweet spot for most photos — the biggest size reduction without visible loss.
Quality is adjusted automatically to get as close to the target as possible. If the target is too small, even the lowest quality may not reach it.
At the same visual quality, WebP is 25–35% smaller than JPEG, and every modern browser supports it. Need a transparent background? Use WebP or PNG.
The most reliable way to cut file size. For photos going on the web, 1920px is plenty; for thumbnails, around 800px.
| File | Before | After | Saved |
|---|
Set a target size in KB and the tool narrows in on the best possible quality that stays under it. Batch-process many images and download them all as a ZIP — everything runs in your browser, so files are never uploaded anywhere. For PNGs, quality settings have little effect; shrinking dimensions or converting to WebP works far better.
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How to use
Add your images, pick a compression mode, and press Compress. The results table shows before and after sizes and the percentage saved for each file, and you can download them one by one or grab everything as a ZIP. Your originals are untouched — a new file is created each time, so if you are not happy with the result, change the settings and press the button again.
All processing happens with your browser's Canvas API. Because files never leave your browser, private photos and unpublished material stay private — and with no upload or download to wait for, even dozens of images finish quickly.
How target-size matching works
Upload limits are everywhere: forum attachments capped at 500 KB, email size limits, store listing requirements. Instead of nudging a quality slider and re-exporting over and over, this tool runs a binary search over quality, up to 8 rounds, to find the highest quality that still fits under your target size.
If the target is unrealistically small, even the lowest quality may not reach it. When that happens, turn on the size limit as well — reducing resolution is far more efficient than crushing quality, and the result looks much cleaner. Here you can only cap the longest side; if you need exact width and height in pixels or crops to ratios like 1:1 or 16:9, use the image resizer instead.
Which format should I pick
WebP
25–35% smaller than JPEG at the same visual quality. It supports transparency and every major browser can read it, so for anything going on the web it is usually the right answer. Some older programs and document editors still cannot open it, though.
JPEG
Opens everywhere. It is the safe choice for email attachments or when you do not know what software the recipient uses. It has no transparency support, so converting a transparent PNG to JPEG fills the transparent areas with white.
PNG
Use it for logos, icons, and other images with flat colors and crisp edges — or whenever you genuinely need a transparent background. PNG is lossless, so the quality setting barely changes its size. To make a PNG dramatically smaller, shrink its dimensions or convert it to WebP.
Troubleshooting
I compressed a PNG but the size did not change
PNG is a lossless format, so the quality slider has essentially no effect on it. As described above, shrink the dimensions or convert to WebP instead. If you do not need transparency, JPEG is also a good option.
Compression made the file bigger
That can happen when an already heavily compressed image is re-encoded. In that case the savings column turns red — just keep using the original for that file.
My transparent background turned white
You most likely converted to JPEG, which does not support transparency. Try again with WebP or PNG.