Why your transparent PNG turns white in JPG
One transparent image, two exports. See what survives the format change—and what cannot come back.
JPG cannot keep a transparent background. In CozyToolkit's image converter, transparent areas become white when you export to JPG. A higher quality setting will not change that; choose PNG or WebP if the background needs to stay transparent.
Download the transparent test image and open it in the image converter. It is a 480 × 320 PNG with empty corners, a blue card and a partly transparent yellow circle.
Export two formats from the same original
- Upload the test image.
- In Output formats, select JPG and WebP. Deselect other formats if you only want these two files.
- Choose Best under Quality, which sets the quality to 95.
- Select Export images. Download each format from the file list, or use Download ZIP to get both.
On a phone, open Adjust to choose formats and quality, then Files to find the individual downloads. Preview format changes which output you are inspecting; it does not remove the other selected format.
The JPG export has a white rectangle around the card. The WebP export keeps the empty corners and translucent circle. Both retain the original 480 × 320 dimensions. Neither needs resizing to demonstrate the difference.
Quality and transparency are separate choices
The quality slider controls the lossy encoding used for these JPG and WebP exports. It does not turn transparency on or off. A quality-95 JPG is still opaque; a lower-quality WebP can still contain transparent pixels.
PNG preserves transparency too and is useful when you want a lossless output. WebP can preserve transparency while using lossy colour compression. The MDN image-format guide describes the formats' capabilities.
The converter currently uses white when flattening JPG output; it has no custom JPG background-colour control. If you need a specific solid background, compose that background behind the image in an editor before converting. A checkerboard painted into an image is different: those squares are ordinary pixels and will remain in the export.
Converting back to PNG cannot restore the cutout
We uploaded the exported JPG and converted it to PNG. The resulting PNG still has an opaque white corner. PNG supports transparency, but the conversion cannot know which white pixels used to be empty and which belong to the artwork.
For the same reason, keep the original transparent file. Changing the extension by renaming a JPG does not convert it, and running the flattened JPG through more formats will not recover its original transparency or lost detail.
Check the file, not just the preview background
A white viewer can make the transparent PNG and opaque JPG look similar. Put the export over a coloured background to inspect the edge and the translucent circle. In the converter, Compare and Result let you inspect the selected output; zoom changes the view, not the downloaded size.
Our results record checks decoded pixels from the actual browser exports made on 2 November 2026. At the top-left corner, PNG and WebP have alpha 0, while JPG and the converted-back PNG have alpha 255. Those values mean fully transparent and fully opaque. This is a transparency check on one small fixture, not a file-size or visual-quality benchmark across formats.