Will the quality drop?

Only where the target format demands it. Some formats compress with loss by design:

• JPG, WEBP, AVIF for images and MP3, AAC for audio are lossy — converting to them makes files smaller at a small cost in detail.
• PNG, TIFF, FLAC, WAV are lossless — nothing is thrown away.

We never re-encode a file twice, and converting a lossy file to a lossless format keeps it exactly as it was — it just won’t bring back detail that’s already gone.