What is taking up the space?
Nobody uploads forty gigabytes to be told it is forty gigabytes.
Storage fills up quietly, and the usual advice is to sort by size and start deleting. That is the wrong question. Most of the space in a photo folder is not in files you do not want, it is in files stored in formats that waste room. This reads a folder on your machine and reports what could be recovered by converting rather than deleting.
What it reports
- Roughly how much you would get back, by format.
- The biggest individual files in the folder.
- Which formats are costing the most space.
- Nothing is converted, moved or deleted. It only looks.
Why this cannot be a web service
- Answering it means reading every file in the folder.
- A server would need all of them uploaded first.
- Nobody uploads forty gigabytes to be told it is forty gigabytes.
- The browser can read a folder directly, so the question is cheap here.
Questions
How do I find what is using my disk space?
Look at formats, not just at size. A folder of PNG screenshots or WAV recordings is usually several times larger than it needs to be, and converting rather than deleting gets the space back without losing anything you wanted to keep.
Are the estimates accurate?
They are estimates and are labelled as such. They come from the format and the file size, using typical ratios: about two thirds off a PNG photograph moved to WebP, about a third off a JPEG. Your files will differ, and the only exact answer is to convert one and look.
Does it upload or change my files?
Neither. It reads names and sizes through the browser’s folder access, which asks your permission first, and reports what it found. Converting anything is a separate, deliberate step.
Why does it not work in my browser?
It needs the File System Access API, which Chrome, Edge and Opera support and Safari and Firefox do not yet. Without it a page cannot read a folder at all, which is a reasonable thing for a browser to be careful about.