Folder Size Analyzer

Folder

Pick a folder. Every file inside it is sized, subfolders included. Nothing is written, deleted, or moved.

folder: —
files: 0

Browser support

Renaming and deleting files where they sit needs the File System Access API, which only Chromium browsers ship. Everything below happens on your machine either way — nothing is ever uploaded.

capability	Chrome	Edge	Firefox	Safari
Open a folder from diskwindow.showDirectoryPicker — Chrome/Edge 86 and later, desktop only	✓supported	✓supported	✗not supported	✗not supported
Rename a file in placeFileSystemFileHandle.move — Chrome/Edge 111 and later	✓supported	✓supported	✗not supported	✗not supported
Delete a file in placeFileSystemDirectoryHandle.removeEntry	✓supported	✓supported	✗not supported	✗not supported
Remember the folder for next timethe handle is kept in IndexedDB on this device; permission is asked again	✓supported	✓supported	✗not supported	✗not supported

detected in this browser

window.showDirectoryPicker …
FileSystemFileHandle.move …
indexedDB …

On Firefox or Safari, or on any phone or tablet, this page can explain the job but cannot do it. Open it on desktop Chrome or Edge.

About this tool

Pick a folder. This page walks it, reads each file's size, and draws a treemap of where the bytes went — the same picture WinDirStat and TreeSize give you, without installing anything. Nothing is uploaded: the walk and the layout run in this tab. The rectangles come from squarify in a shared engine; this page does not invent its own geometry.

Treemap, largest files, extensions

Each rectangle is a folder or a file, area proportional to bytes. Click a folder to zoom in; use the breadcrumb or Up to climb out. Beside the map: the largest files, and how many bytes sit in each extension. Tiny items are left as gaps on purpose — they are still counted in the hidden line, not stretched to fill the hole.

Read-only

This page never writes, deletes, or moves a file. A file whose size cannot be read is listed on its own and is not counted as zero bytes. For copies of the same file eating the disk twice, open Duplicate File Finder. Folder Hash writes a SHA256SUMS file; Folder Compare checks two trees against each other.

Frequently asked questions

Are my files uploaded to draw the map?

No. The walk, the size reads and the treemap layout all run in your browser. The page is a static file with no server behind it, so there is no upload path even in principle.

Why are there empty gaps in the treemap?

Items below a size threshold are laid out and then removed, on purpose. The hole is the bytes that are still there but too small to draw as a usable rectangle. The line under the map says how many items that is, and how many bytes. Filling the hole would pretend those files were larger than they are.

What does unreadable mean?

The walk found the path but the browser could not read its size (gone, locked, or changed under the scan). That is not a zero-byte file. Unreadable paths are listed on their own so the total does not swallow them as empty.

Does this delete or move anything?

No. The page is read-only. It cannot write, delete, or move a file. If the fat is copies of the same file, Duplicate File Finder is the tool that can delete extras — this one only shows where the bytes went.

Which browsers does it work in?

Chromium desktop browsers (Chrome, Edge, Brave) can pick a folder with the File System Access API and remember it for next time. Firefox and Safari can still scan through the file input (webkitdirectory); they just cannot remember the folder. The support table on the page reports what this browser actually has.