Folder Size Analyzer

About the folder size analyzer

"My disk is full" is almost never answered by looking at one folder. The space is somewhere three or four levels down, in a folder you have not opened in a year, and the built-in properties dialog only tells you the size of whatever you right-clicked.

This tool rolls every file's size up through all of its parent folders, so each folder reports the weight of its entire branch rather than just the files sitting directly in it. Then you follow the biggest number downwards until you reach the thing that is actually large.

Pick a folder and it measures everything underneath. It is read-only: nothing is uploaded, nothing is moved and nothing is deleted.

Three ways to look at the same scan

• Folders, biggest first — what each subfolder weighs as a share of the folder you are in. Click any row to go into it, and use the trail at the top to come back
• Biggest files — the largest individual files anywhere in the tree, wherever they are hiding. This is the view that finds the 8 GB virtual machine image you forgot about
• Space by file type — the total per extension. The one that reveals "40 GB of .mp4" or a cache full of .tmp files

The percentage on each row is a share of the folder you are currently looking at, not of the whole drive, so the bars stay meaningful as you go deeper.

How to use it

• Click Choose a folder and pick the one to measure. Your browser will ask permission to read it
• Read the summary — total size, file count and folder count
• Start in Folders and click your way down the biggest rows
• Switch to Biggest files or Space by file type when the folder view has narrowed things down
• Copy the current view, or download the CSV for a spreadsheet

It works in every browser

This is the one folder tool with no browser caveat worth worrying about.

Chrome, Edge and Opera let the page walk the folder directly. Firefox and Safari use an older mechanism that hands over a list of files with their paths — and sizes are all this tool needs, so the numbers come out identical.

The only difference is the folder count: a folder containing nothing at all is invisible to the older mechanism. Since an empty folder uses no space, every size on the page is still exact. The tool says so rather than quietly reporting a smaller tree.

What people use it for

• Finding out why a drive filled up without any obvious change
• Locating the one enormous file — a disk image, a video export, a database dump
• Deciding what to move to an external drive before a backup
• Checking whether a cache or log folder has quietly grown to gigabytes
• Working out which project folder is worth archiving
• Auditing a shared drive before a cleanup, then exporting the CSV as evidence

Reading the numbers

• Sizes are bytes on disk as the browser reports them, which is the file's real length. Your operating system may show a slightly larger "size on disk" because it rounds every file up to a whole allocation unit — on a drive with many tiny files that difference adds up
• A folder's size includes everything beneath it. The percentages within one view therefore add up to roughly 100%, with the remainder being the files sitting directly in that folder
• Space by file type counts every file in the whole tree, not just the folder you are looking at

Good to know

• Works on Windows, macOS, Linux and ChromeOS — it is a web page, so there is nothing to install. It cannot work on iPhone, iPad or Android: mobile browsers have no way to hand a folder to a web page
• Nothing is uploaded. The whole scan happens in the page — you can watch the network tab
• Read-only by design. This tool has no way to delete or move anything, which is deliberate for something you point at a full drive
• Very large folders are capped at 200,000 items so the page cannot freeze
• The Biggest files view shows the top 500 on screen; the CSV always contains every folder
• Scanning a large drive takes a moment because every file has to be asked its size. A progress bar shows how far it has got
• Shortcuts and symbolic links are counted as the small files they are, not as the thing they point at, so nothing is double-counted

Related tools

• Duplicate File Finder — the other big source of wasted space
• Empty Folder Finder — clear the clutter once the big items are gone
• Folder & File List — list everything in the folder
• Sort Files Into Subfolders — tidy the folder you just measured