Field note · Files
A folder size map is a prioritization tool, not a delete button
Published: September 9, 2026 · Maintained by: Jisung Kim · AI assistance and release-check practices are disclosed in the editorial policy. This note documents WEBBE-B tool behavior, design choices and verification practice.
FolderHeat answers a narrow question: among the files a user explicitly selects, where are the bytes concentrated? That question is more useful than it looks because storage cleanup often starts with guesses. People delete dozens of small documents while one export directory or video cache accounts for most of the space.
Start with magnitude, not annoyance
A folder can feel cluttered because it contains thousands of files, yet occupy little space. Another folder can contain only six video files and dominate the disk. Counting files and measuring bytes are different views. FolderHeat rolls file sizes into parent folders and extensions so the first decision can be “where is the largest opportunity?” rather than “which folder looks messy?”
What the browser is actually measuring
The browser exposes metadata for the files the user selects, including file size. That size is the logical length of the file contents. It is not a complete model of physical disk allocation. File systems may use allocation blocks, compression, sparse files, deduplication, snapshots or cloud placeholders. A 1 GB logical file can therefore occupy a different amount of physical storage depending on the underlying system.
For ordinary photos, downloads and project files, logical size is still a useful prioritization signal. The important part is to label it honestly: the treemap is a map of selected file bytes, not a forensic disk-usage scanner.
Why treemaps help and where they mislead
A treemap gives large folders large rectangles, making concentration visible quickly. It is excellent for questions such as “is this backup dominated by videos?” or “which export directory grew unexpectedly?” It is less useful for comparing many tiny differences. A small rectangle may still contain a critical database, configuration file or document.
Visual area also encourages a destructive bias: the biggest block looks like the obvious deletion target. The safer interpretation is “inspect here first.” Size says nothing about replaceability.
Extension summaries are clues, not classifications
Grouping by extension can reveal that .mov, .zip or .psd files account for most of the selected bytes. But extensions can be missing, misleading or reused. A file ending in .jpg is probably an image, yet the extension alone should not decide whether it can be removed. The summary helps form a question; it does not answer it.
A safer three-pass audit
First, export an inventory with FolderList if you want a before-state record. Second, use FolderHeat to identify the largest folders and files. Third, when repeated copies appear to be the issue, verify them with ExactDupe rather than assuming matching names are duplicates.
This sequence preserves context. If something is moved or deleted later, the inventory makes it easier to reconstruct what was present, while the size map explains why a folder was investigated in the first place.
Example: a photo-project archive
Suppose a 180 GB project folder contains RAW files, edited TIFFs, web exports and two backup exports. FolderHeat shows that exports/final-v2/ and exports/final-v3/ together occupy 72 GB. That does not mean one can be removed. It tells you to compare them. If ExactDupe later shows that 31 GB is byte-for-byte repeated, you now have evidence for a cleanup decision. If the exports differ, the apparent duplication was only visual similarity.
Browser boundaries matter
FolderHeat cannot enumerate a drive without permission, inspect operating-system protected areas, or know the storage used by hidden snapshots. It sees the files the browser is allowed to expose after user selection. That limitation is also a privacy property: the site cannot silently roam through unrelated folders.
The useful output is a question list
A good storage report should leave you with a short list of places to investigate: the largest folder, the largest individual files, unexpected extensions and areas with possible duplicates. The destructive action belongs after those questions have been answered.
Logical bytes are not disk allocation
Browser-visible file sizes normally represent logical file length, not the exact number of storage blocks consumed on a particular filesystem. Sparse files, compression, deduplication and allocation-unit rounding can make operating-system “size on disk” differ from the sum shown by a browser audit. FolderHeat therefore uses its totals for relative triage—finding which selected folders contain the most data—rather than claiming to reproduce every filesystem accounting detail.