Learn why a compression export can increase file size and how to compare formats, quality settings and image dimensions before saving a result.
A new encoding is not always a reduction
Image Compressor creates a new JPEG or WebP representation of the selected image. It does not simply remove a fixed percentage of bytes from the original file. If the source was already encoded efficiently, the new settings may produce a larger result.
Small graphics and photographs can also behave differently. An image with a few flat colors may already be compact in its original format. Converting it to another format does not guarantee a smaller file, even when the tool is called a compressor.
Read the actual size comparison
Generate the result and compare the Original and Result values. ToolNivo explicitly says when the output is not smaller instead of presenting every conversion as a saving. In that case, there is no need to download the new copy unless its format serves another purpose.
Try a lower quality setting and inspect the preview again. Alternatively, compare JPEG with WebP from the same selected source. Keep transparency in mind: a smaller JPEG may still be unsuitable if it replaces a required transparent background with white.
Check whether the dimensions are excessive
A large pixel count can be more important than a small quality adjustment. If a photo is much larger than its intended placement, resize it first. For example, preparing a proportionate 1200-pixel-wide copy may be more useful than keeping a much wider image and repeatedly reducing encoding quality.
The exact savings depend on the photograph. Do not assume that halving a dimension or changing a slider by ten points will produce a fixed file-size reduction. Measure the result and check that it remains usable.
Keep the original when it is better
An optimization attempt can reasonably end with retaining the source. Compare the file your recipient actually needs, not just the newest export. Avoid uploading a heavier or visibly damaged copy merely because it came from a compression tool. Save promising alternatives under different names and remove unnecessary duplicates only after deciding which version to use.