Free Online Image Compressor
Use this online image compressor to reduce image size with a quality setting, optional resize and a clear before-and-after comparison.
Image Compressor
Runs online, your files remain privateYour image is processed locally and never uploaded.
Your file stays on this device. Image data is processed in your browser and is not uploaded to GZ.
About this tool
This image compressor decodes your selected file on your device, draws it to a browser canvas and encodes a new file in the format you choose. The original stays on your device. JPEG and WebP use a quality setting; PNG output is lossless through the browser canvas and its quality slider has no effect.
The result depends on the source image, dimensions, format and browser encoder. Re-encoding an already optimized image can make it larger. Compare the preview and file sizes before downloading, and keep the original if visual fidelity is critical.
How to use it
- Choose a JPG, PNG or WebP image, or drop it into the box.
- Pick an output format and adjust quality. You can also set a new width or height.
- Review the preview and size comparison, then download the optimized copy.
Frequently asked questions
Are my images uploaded?
No. Files are decoded and re-encoded in this browser tab; GZ has no image upload endpoint.
Is compression lossless?
JPEG and WebP quality encoding is lossy. PNG canvas output preserves pixels as PNG, though browser re-encoding may not reduce its file size.
Why is my output larger?
A source file may already be highly optimized, or the chosen output format may suit that image poorly. Try another format or keep the original.
Can I compress multiple images at once?
This image compressor processes one file at a time. Bulk and batch image compression are not available yet; download one result before selecting another image.