Compress photos to a size, not a guess
Photo compression offers four balances — Recommended, High quality, Small file and Smallest — each with a size estimate worked out from your own files, so you can see the trade before choosing. If a website demands a limit such as "under 500 KB", say so: ToolGPT lowers the quality step by step until the photo fits, and if it cannot get there it tells you the smallest size it reached rather than handing back something too big.
It will not pretend. If a photo would not come out smaller than it already is, the job reports that instead of returning a file that is the same size.