How do I repair a corrupted ZIP file?

Copy the file first, then upload it to a repair tool that scans the archive for every local header and rebuilds the central directory and EOCD record around the surviving entries. This recovers most ZIPs damaged by an interrupted download. If you prefer the command line, zip -FF does the same rebuild.

Can every corrupted ZIP file be repaired?

No. When only the archive's index is damaged and the entries are intact, a rebuild recovers everything. But if the file was truncated in transit, the missing bytes were never written and cannot be restored. In that case a fresh copy from the source is the real fix.

What does a CRC error mean when I unzip a file?

A CRC error means the compressed data for that entry did not match its stored checksum, so the file's contents are damaged rather than just mis-indexed. A rebuild fixes archive structure but cannot repair the bytes of a CRC-failed entry. Re-download that file or extract the partial data.

Does the repair tool install anything or upload my files?

The repair ZIP tool rebuilds the archive in your browser, so there is nothing to install. It scans the local headers, reads the compressed data behind each one, and writes a fresh archive with a clean central directory that opens in any unzip program.

How to Repair a Corrupted ZIP File

Q: Is it better to repair a ZIP or re-download it?

If the archive was truncated during download, re-downloading is cleaner because it replaces the missing bytes with real ones instead of working around their absence. If the source is gone or the download is slow, repairing the copy you have recovers whatever data actually survived.

Learning how to repair a corrupted ZIP file is far less daunting once you understand where the damage usually sits. A ZIP archive that refuses to open, throws a "cannot open file as archive" error, or reports that the central directory is missing is rarely as lost as it looks. In most cases the files packed inside survived intact and only the archive's index was scrambled. This guide walks through repairing a corrupted ZIP file the reliable way, starting with the fastest option and moving to manual fallbacks when you need them.

You can follow along with the repair ZIP tool, which rebuilds a damaged archive in your browser without installing anything. But first it helps to know what a ZIP file actually is, because that explains why repair works at all.

What Lives Inside a ZIP File

A .zip is not one solid block of data. Each file you add is stored as its own unit: a local header that names the file and describes how it was compressed, followed by the compressed data itself. Then, at the very end of the archive, sits a central directory and an end-of-central-directory (EOCD) record. Together these act as the table of contents, listing every entry and pointing to where it begins.

When an unzip program opens an archive, it reads that table of contents first, at the end of the file, and uses it to jump to each entry. This design is efficient, but it has a weakness: if the tail of the file is damaged or missing, the reader loses its map even when every entry is still present. That is exactly the situation a rebuild is built to fix.

How to Repair a Corrupted ZIP File: Step by Step

The most dependable route runs entirely in the browser, so start here.

Make a copy first. Duplicate the damaged .zip so the original stays untouched while you work.
Open the repair tool. Go to the repair ZIP page.
Upload the archive. Drag the .zip into the upload area or browse to select it.
Run the rebuild. The tool scans the archive for every local header it can find, reads the compressed data behind each one, and reconstructs a fresh central directory and EOCD record around the survivors.
Download the result. Save the rebuilt archive under a new name.
Extract and verify. Open the new .zip and confirm that the files you need are present and readable.

For the large family of ZIPs damaged by an interrupted download or a failed transfer, this single pass is usually enough. The index gets rebuilt from the intact entries, and the archive opens normally again.

What to Expect From a Rebuild

A rebuild recovers what is physically present in the file, not what should have been there. If all the compressed data arrived and only the directory was corrupt, you typically get everything back. If part of the archive never made it to disk, the tool salvages whatever it can and skips the rest. That is not a flaw in the tool; missing bytes cannot be invented. A partial recovery that returns nine of ten files is still a genuine win over an archive that would not open at all.

Manual Option One: zip -FF (Info-ZIP)

If you have a terminal, Info-ZIP's command-line tools include a purpose-built repair mode. The fix-fix flag scans the archive from the front, finds each local header directly, and writes a rebuilt copy with a fresh central directory:

Run zip -FF broken.zip --out fixed.zip
The tool walks the local headers one by one, and for each entry it may ask you to confirm whether the data looks valid.
The result is written to fixed.zip, leaving your original untouched.

This is the same principle the browser tool uses: ignore the damaged index at the end and rebuild it from the entries at the front. On Linux and macOS the zip command is usually already installed or a package away; on Windows it ships with tools like Cygwin or Git Bash.

Manual Option Two: 7-Zip Open and Extract

7-Zip is unusually forgiving with damaged archives, which makes it a strong second opinion. Rather than repairing the file, it often lets you extract straight from the broken archive:

Right-click the .zip and choose 7-Zip > Open archive. Even when other tools refuse, 7-Zip frequently displays the file list.
Select the files you can see and extract them to a folder.
7-Zip flags any entry that fails a data check, so you learn immediately which files are clean and which are damaged.

If 7-Zip shows the contents, you may not need a formal repair at all; you can simply pull the readable files out and move on. It is a fast way to rescue an archive whose central directory is broken but whose entries are fine.

Manual Option Three: Re-Download or Re-Transfer

Before spending long on a stubborn archive, ask where it came from. If you downloaded it, a fresh download is often the cleanest fix of all, because it replaces missing bytes with the real ones instead of working around their absence. This matters most when the archive was truncated, meaning the transfer stopped early and part of the file simply never arrived. No repair can restore data that was never written, so a clean copy from the source beats any reconstruction.

When you re-download, use a stable connection, let the transfer finish completely before opening the file, and if the source offers a checksum, compare it against your copy to confirm the download is bit-for-bit correct.

Understanding CRC Errors

Every entry in a ZIP carries a CRC checksum, a fingerprint of its original contents. When an extractor reports a CRC error, it means the compressed data for that file was decompressed but did not match its fingerprint, so the bytes themselves are damaged rather than merely mis-indexed. A rebuild can restore the archive's structure, but it cannot repair the contents of a CRC-failed entry. For that file, your realistic options are a fresh copy from the source or extracting the partial, imperfect data if it is better than nothing. Our guide on recovering files from a damaged ZIP covers this salvage work in detail.

Choosing the Right Route

In practice, most corrupted ZIPs fall into a clear order of attack. Start with the repair ZIP tool for a fast browser rebuild. If you prefer the command line, reach for zip -FF. If you just want the files out, let 7-Zip open the archive and extract what it can. And if the file was truncated in transit, re-download it from the source. To avoid repeating the whole exercise, our guides on why ZIP files get corrupted and how to prevent ZIP corruption explain the causes and the habits that keep archives healthy.

Conclusion

Repairing a corrupted ZIP file comes down to one insight: the damage almost always lives in the index at the end, while your files sit safely at the front. Rebuilding that index from the surviving local headers brings most archives straight back. Copy your file, run it through the repair ZIP tool, and fall back to zip -FF, 7-Zip, or a clean re-download when you need to. Whatever route you take, work on a copy so a failed attempt leaves you no worse off, and start your repair now.