Decide what you mean by without losing quality before choosing compression settings. Pixel-identical preservation and an image that looks acceptable at its intended display size are different goals. Lossless encoding preserves decoded pixel data, while lossy encoding can reduce information. A high JPEG quality setting is not proof of lossless preservation.
Define the acceptance condition
For diagrams, screenshots or production assets, you may need exact pixels or reliably crisp text. For a photographic preview, some invisible-at-use-size changes may be acceptable. Metadata, color handling and animation are separate requirements; pixel preservation alone does not establish that every source feature remains.
Choose an export path that fits the goal
PNG is a lossless image format, while JPEG normally uses lossy compression. WebP and other formats can have different encoding modes, so check the specific encoder rather than assuming a format name or a tool mode guarantees exact preservation. Browser decoding, color conversion and resizing can change pixels before encoding occurs.
Compare from the unchanged original
Illustrative process: export two photographic candidates at identical dimensions, compare them at their destination size and then inspect critical details at full size. Adjust quality until the required detail survives. If the smallest acceptable export is larger than the current file, keep the current delivery file unless another requirement makes conversion necessary.
For a strict pixel-identical requirement, use an appropriate lossless workflow and compare decoded pixel values. A visual side-by-side check cannot prove equality. Keep the original because higher quality cannot reconstruct detail lost in an earlier export.
Change one variable at a time
Reducing dimensions, changing format and lowering quality all influence the result. Isolate them during comparison so you know which change helped or damaged the image. There is no universal compression ratio or quality number that applies to all photographs. Finish by checking actual bytes, dimensions and appearance in the receiving application.