Find Duplicate Files in ZIP

This tool reads a ZIP in your browser and surfaces files that share an identical uncompressed size, grouping them so you can see redundancy at a glance. It fits the moment before you ship or archive a ZIP: a developer consolidating a project export that accumulated copied assets across folders, or someone auditing a deliverable before sending it to a client. Because it reports rather than rewrites, it works well as a review step in a larger cleanup flow.

It also suits backup and archiving housekeeping. Long-lived backup ZIPs tend to collect the same document, image, or library file saved into several directories over time. Scanning surfaces those size-matched groups and totals the space they waste, which helps you judge whether a cleanup pass is worth doing. For data prep, it is a quick way to flag accidental re-exports before a dataset gets passed downstream.

The output is a flat read of file paths and sizes, so it is equally useful for office and admin work: tidying a shared resource ZIP, or sanity-checking a coursework or submission archive where the same attachment may have been added twice. It is not a content-identity tool, so treat it as a triage signal, not a verdict.

Drop or select a single .zip file. The tool opens it locally, lists every non-directory entry, and groups files by their uncompressed size. Any group with more than one file is reported as a potential duplicate set, sorted so the groups wasting the most space appear first. You then see files scanned, duplicate groups, redundant file count, and total wasted space, with each group expanded to show its full internal paths.

Detection is size-based. Files with byte-identical uncompressed sizes are flagged together; directory entries and zero-byte files are skipped so empty placeholders do not create noise. The tool does not compute content hashes, so it cannot confirm two same-sized files are truly identical, and it will not match identical files that differ in size by even one byte. It reads .zip archives only.

When duplicates are found, you can export a CSV report listing each group, the per-file size, the file count, the wasted bytes, and the pipe-separated paths, plus totals. The tool does not delete anything or produce a cleaned ZIP — your original file is never modified. To actually remove copies, take the report to the Remove Files from ZIP or Clean ZIP tools.

The core caveat is false positives. Two genuinely different files that happen to share a size — common with small icons, fixed-length records, or padded assets — will land in the same group even though they are not copies. Always read the paths and, where it matters, open or compare the files before assuming they are interchangeable.

The flip side is missed duplicates. Identical content saved with different compression or trivially different sizes will not be grouped, so a clean scan does not guarantee a ZIP has no redundancy. The summary reports size matches, not name matches; despite what the older description suggests, this build does not separately flag same-name files or offer in-tool removal.

A practical mistake is treating the wasted-space figure as a deletion plan. It assumes one copy per group is kept, but it does not know which copy you need, and some same-size groupings are coincidental. Decide per group which paths are real duplicates rather than acting on the headline number.

Start with the summary: check that files scanned roughly matches what you expect in the archive, then open the largest groups first since those drive most of the reported waste. For each group, read the full paths — duplicates spread across folders are usually intentional copies, while same-size files in unrelated locations are often coincidences worth verifying by opening them.

Because removal happens in a separate tool, plan deletions deliberately: note which path in each group you intend to keep, confirm the others are truly redundant, and keep the original ZIP as your fallback since this tool never alters it. The exported CSV is a useful worktable for marking decisions before you delete.

For official, financial, or legal archives, do not rely on size matching alone. Same-size is a hint, not proof of identical content, so manually open and compare any files you plan to remove, and verify the kept copy is the correct, current version before discarding anything.