Quality can change after conversion, but it depends on the file type and settings. Some formats make files smaller by removing small details, while others keep more of the original information. This applies to images, audio, video, and documents. In general, higher quality keeps more detail but creates larger files, while lower quality makes smaller files with less detail.

Output size can increase when the new format keeps more data, or when you move the quality slider higher. If a file is already compressed (like JPG, MP3, or MP4), converting it again at high quality can make it larger, even when quality does not visibly improve. Some outputs, like PDF layouts or less-compressed audio and video formats, are naturally larger by design.

Choose higher output quality when you need sharp detail, cleaner sound, or better results for printing and editing. Choose lower quality when smaller files matter more, such as for email, messaging, and faster uploads. In most cases, a medium setting gives the best balance between file size and quality, while very high settings can increase size without a noticeable improvement.

Reducing file size usually means balancing compression and detail. Lossless compression can save space while keeping more of the original file, but the size reduction is often limited. Larger savings usually come from lossy compression, where some visual or audio detail is removed. The best setting depends on whether you care more about smaller files, higher quality, or easier sharing.