On September 30, 2026, I released Karuku, a browser-based tool for compressing and resizing images. Here is what it does, why the processing stays in the browser, and the limits I confirmed before release.
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On September 30, 2026, I released Karuku, a tool for compressing and resizing images. When you prepare an image for a blog, social media, or a slide deck, making the file smaller is often not enough: the dimensions, quality, or transparency may still be wrong for where it is going. Karuku lets you pick a purpose, compare the result with the original, and save it, all inside your browser.
https://oka-project.com/en/tools/image-resize
What Karuku does
Karuku is a free tool for getting images to a target size or file size. It supports:
- converting between JPEG, PNG, and WebP
- presets for common purposes
- compression with a maximum file size you set
- saving several images at once as a ZIP
You can compare the original and the output side by side, and you can strip camera metadata (Exif). Output quality depends on the source image and the settings you choose, so the tool is designed around checking text and edges in the result after saving.
Why the processing stays in the browser
Shrinking an image should not have to mean sending unpublished slides or personal photos to a separate conversion server. Karuku handles the core image conversion in the browser and does not upload image files to a conversion server.
That said, "processed in the browser" is not a guarantee of security as a whole. How your device and browser extensions are managed, and what happens to the files you save, are separate questions you still need to check.
What I was careful about
PNG is a lossless format, but if colors are reduced or the image is resized first, the original pixels change. Karuku also takes different processing paths depending on the number of colors and the file size cap, so I do not describe it as "always perfectly lossless if you export PNG."
Offline support is not just a label in the UI. In a check in October 2026, I confirmed that resizing, saving, and ZIP export all worked without a network connection. You need to open the page once while online so the processing data it needs is loaded. If you clear the browser's site data, you will need to load it again.
Where it fits, and where it does not
Karuku is a good fit when you want to resize images for a blog or social media, cut the file size of photos, convert formats, and remove camera metadata in one place. It does not guarantee that every image can hit a target file size and still look exactly like the original. For semi-transparent areas in logos, or small text in screenshots, always compare the result.
The workflow I recommend: keep the original, choose a purpose, then check the exported image.