Choosing an image format is a tradeoff between size, appearance and compatibility. The best format depends on the picture and where it will be used.
JPG works well for photographs. Its compression removes some image information, which can produce visible blocks around text and edges at low quality. Avoid repeatedly editing and saving a JPG, because each generation can lose more detail.
PNG supports transparency and preserves exact pixel values. It is useful for screenshots, interface graphics and illustrations with flat colors. Photographs saved as PNG can be much larger than equivalent JPGs.
WebP supports transparency and often produces compact images. Check that your destination accepts it before converting a batch. Changing a filename extension does not convert the underlying image; an actual encoder must create a new file.
Resize images to the dimensions you need before increasing compression. Sending a 6000-pixel photograph for a small thumbnail wastes bandwidth. Keep an original copy and inspect fine details, hair, text and gradients after conversion.
Allnira uses your browser's image encoders. Animated formats are flattened to one frame in the image converter, and color handling may differ across browsers. For professional print production, preserve your source files and use a workflow that explicitly manages color profiles.