Compress locally, not on a server
CollagePlus decodes and re-encodes images inside your browser. The Worker path keeps batch processing away from the interface thread, while Cancel stops the active queue and preserves completed results.
For JPG and WebP, the compressor adjusts encoding quality first. If a file still cannot meet the selected target, it may reduce pixel dimensions and clearly labels that result as resized. PNG color reduction and resizing are used for PNG output.
Keep or change the format
The default keeps JPG, PNG and WebP files in their original format. Choose JPG for broad compatibility; transparent pixels become white. Choose WebP for stronger compression and transparency support.
Already optimized images
If re-encoding cannot make a file smaller, the original is retained and marked as unchanged. You can still include it in a batch download, or try another format for a smaller result.