The original may already be efficient
A source downloaded from a website, messaging app, or marketplace may already have been resized and compressed. Encoding it again at a high quality can add overhead or preserve more data than the previous encoder did.
- Compression is not guaranteed to reduce every file.
- Keep the original when it is smaller and looks acceptable.
Changing format changes the comparison
A detailed PNG photograph can become much smaller as WebP, while a simple transparent graphic may behave differently. Metadata, alpha channels, and encoder settings also affect the final bytes.
- Compare like-for-like dimensions.
- Check whether transparency is required.
- Do not judge by extension alone.
Reduce the right variable
If quality adjustments do not help, choose a smaller maximum dimension. If dimensions must remain unchanged, try a slightly lower quality and inspect fine detail before accepting the result.