How to repair zip files?

[marrysimon]

Anybody can help me to repair corrupt zip files and remove error message “the compressed (zip) folder is invalid and corrupted"? I have made an effort many times to fix corrupt zip file but always show this error message.

[tomos]

I've never used it but have read a good review - Diskinternals (free)
http://www.diskinternals.com/zip-repair/

That good review was here:
http://www.techradar.com/news/software/how-to-repair-a-broken-zip-file-986146#articleContent
-- doesnt seem to mention which version of windows they used it on.

[Shades]

Always use the latest version of your favorite zip/unzip software. It might be that the person creating the archive has used an option not yet available in the version you have running and you will get this type of error message.

One can also try to use a different piece of software to extract the archive. In my experience the latest (portable) version of 7-zip (www.7-zip.org) is quite able in getting archives extracted. Another tool would be Universal Extractor. These are free to use, but will gladly accept your donation(s).

Too bad you missed out on deals on the BitsDuJour website. Not that long ago they offered a free version of DataNumen Zip repair. That might be an option for you as well. However, I don't know how good that software is at what it does as I usually re-download he zip file again if these kind of messages pop up in my portable versions of 7-zip and Universal Extractor.

[Ath]

... remove error message “the compressed (zip) folder is invalid and corrupted"? ...

Never, ever, use Windows Explorer to unpack zip-files (the Compressed Folders feature of Windows Explorer). That cr@p-tool is unable to pack or unpack a zip-file correctly.
Always use any of the (free) archive tools designed for that purpose.

I'm personally a fan of 7-zip, and (have used and) know that peazip is working just as well, but any other compression tool should do fine.

[Jibz]

This zip format does not contain any recovery data I am afraid. The best you can hope for, is being able to decompress files skipping the parts that are corrupted.

If the data record that lists the files is intact, you can try 7-Zip or Info-ZIP UnZip, which both do not mind continuing after a corrupt file.

If not, you will probably need some tool to repair it. WinRAR has some support for reconstructing, and searching for 'zip repair' gives some hits that might work as well (Zip Repair as mentioned by tomos might be worth a shot).

[techidave]

+1 to Shades and Ath's response.  i was getting this same error while using the Win 7 built in utility.    Then on a suggestion from a friend I tried 7-zip and it was able to uncompress it without any problems at all.  

I believe they used a newer utillty to compress it the win 7 tool just couldn't handle it.

[Renegade]

As above...

Most good ZIP utilities will either make this invisible to you or prompt you to repair an archive. If they don't work, you're hosed.

Most ZIP programs include a lot of error finding code to fix common problems and some not-so-common problems. However, as noted above, ZIP files do not contain recovery information, so if a utility can't recover it, the data is lost (without massive effort that probably isn't worth it).

[IainB]

Interesting. I would usually remove WinZip from the XP and let the standard system ZIP functionality in Windows Explorer do the work - mainly because Search/Index could read files in Windows-created ZIP archives, but not necessarily in ZIP archives created by proprietary ZIP archiving tools.
I never had a "corrupt" ZIP file, and I do not see how such corruption could occur, or even that it should (other things being equal and no system problems). However, I did find that sometimes ZIP archives created by proprietary ZIP archiving tools could not be read by Windows Explorer, but could be opened by (say) 7-ZIP without any difficulty.

Similarly, using Win7, I have never had any difficulty with the standard system ZIP functionality.

There was a post made earlier - a couple of days ago - in this thread that I think might have been deleted as spam, or something, but actually it seemed helpful and pointed to some good references, so I have copied it below. Malwarebytes didn't ring any alarms when I followed the link given. The notes seem genuine enough.

bar_bak@DonationCoderForumRssNoEmail.com
Dear friend,
Corrupted zip files can be repaired with the help of manual solution using WinRar application. It has inbuilt tool that repairs your damaged file and makes it accessible. Visit the link given below to know the steps required to execute:

http://nalavadebela.wordpress.com/2014/04/05/how-to-repair-a-corrupted-archive-file/

These steps are very easy and no such technical knowledge is required to execute this manual process. You can also read detailed description about corruption and solution to repair file in this blog post.

[xtabber]

WinRAR can create RAR files with an internal recovery record that slightly increases the archive size, but lets you to recover the contents of damaged RAR archives when the corrupted or missing segment is no larger than the size of the recovery record.

However, according to the WinRAR help file, "ZIP archive format does not support the recovery record."

[IainB]

^^ Good point re WinRAR and the "recovery record". I vaguely recall that as being amongst its list of features when I used to use it some time ago.

I just now did a DuckGo search on "Repair corrupt ZIP" and came up with several hits, including this interesting one about ZIP Repair Pro:

Repair Zip Files using Zip Repair
Zip Repair
Zip Repair is a utility that will repair corrupt Zip files. Usually a corrupt Zip file gives the error message:

"Cannot open file: it does not appear to be a valid archive"

Zip Repair creates an error free backup of your original file for instant access, or you can extract files directly from a corrupt ZIP file to your hard drive. No special skills required. A simple user interface with full install / uninstall support.

Version 5:

• New: Repair a Zip file or extract files directly from the ZIP
• New: Zip Repair will fix CRC errors in .zip files so that data can still be uncompressed
• New: Zip Repair supports spanned zip volumes. You can now repair and extract from a spanned zip set even if part of the set is missing
• New: Full support for the Zip64 format
• New: Support for huge file sizes 2GB+ (as long as you have the disk space)
• New: Batch repair multiple ZIP files

It doesn't say whether it can recover all of a corrupted ZIP file's contents 100% of the time, but it could be worth a try if you are stuck with a truly corrupted file that (say) 7-ZIP cannot open/read or where other approaches suggested above have drawn a blank.

A year or so past, I downloaded a corrupted executable install file for Stickies. It executed fine but wouldn't install properly - the install got stuck in a program loop. So I asked the author (Tom Revell of Zhorn Software) about it and he was mystified. He sent me a ZIP file (which installed just fine) and asked me to send him a copy of the installer file that I had downloaded. It turned out that it had a different checksum to the one on the download server, so it must have got corrupted in transmission, somehow, and yet it still executed with no error message.
After that experience, I now usually look for the checksum of downloaded executable and other archive files, for file verification, and also - just in case - try to open and test them using 7-ZIP.

[Innuendo]

WinRAR can create RAR files with an internal recovery record that slightly increases the archive size, but lets you to recover the contents of damaged RAR archives when the corrupted or missing segment is no larger than the size of the recovery record.

However, according to the WinRAR help file, "ZIP archive format does not support the recovery record."

This is why I always use RAR instead of zip when archiving my own stuff. I think the latest zip archive format version has offered some rudimentary recovery data to created archives, but it's nothing nearly as robust as how RAR handles things. Oh, and you can control the size of the recovery record RAR adds as well.

Repairing zip files is always a dicey proposition. It rarely works. I think you'd get better odds in Vegas.

[IainB]

I wonder whether we aren't discussing a non-existent problem.
It might be simply a case where, as @Shades put it:

Always use the latest version of your favorite zip/unzip software. It might be that the person creating the archive has used an option not yet available in the version you have running and you will get this type of error message. ...

Has anyone in this discussion thread actually had a repeatable case where their system created a ZIP file that was later found to be invalid and/or corrupted?

[MilesAhead]

If for some reason you would rather not use WinRar for a particular file set you can still build a file set with recovery info using QuickPar and PAR2 files.  For example if you wanted to include par2 files for a data dvd.

Although the most common use in my experience is with file sets posted to usenet.  In most cases the file set is rar files but it doesn't have to be. 

[Edvard]

...

Has anyone in this discussion thread actually had a repeatable case where their system created a ZIP file that was later found to be invalid and/or corrupted?

Yes, but it was one of two different scenarios, and it was quite some time ago, circa 2001 or so when I was still running Win95 or 98.

1- Zip file that was apparently the victim of a bad sector that hadn't been detected yet.  
    Zipped, tested OK, powered down, next day no zippy pour moi.
2- Accidentally unplugged the computer while creating a zip archive.  
    I thought it had finished before the power went, but apparently not.  

[IainB]

@Edvard: Those were anomalous instances and not repeatable. I could be wrong, of course, but that's what I was trying to point out in my earlier comment - i.e., that this thread is about something (an error or a fix for an error) that doesn't happen under normal circumstances, or isn't actually required, and which couldn't be mitigated or repaired if it occurred anyway.

In other words, there is likely to be no need to repair .ZIP files, as you would probably only get damaged ZIP files from an irreversible anomalous and non-repeatable) event, and due to the simple structure of .ZIP files, you will be unlikely to be able to recover/repair/reconstruct the lost/corrupted data - you couldn't "magic" the data out of nowhere.

[Renegade]

@Edvard: Those were anomalous instances and not repeatable. I could be wrong, of course, but that's what I was trying to point out in my earlier comment - i.e., that this thread is about something (an error or a fix for an error) that doesn't happen under normal circumstances, or isn't actually required, and which couldn't be mitigated or repaired if it occurred anyway.

In other words, there is likely to be no need to repair .ZIP files, as you would probably only get damaged ZIP files from an irreversible anomalous and non-repeatable) event, and due to the simple structure of .ZIP files, you will be unlikely to be able to recover/repair/reconstruct the lost/corrupted data - you couldn't "magic" the data out of nowhere.

IainB is right.

Compression relies on entropy (or many forms of compression anyways). This is a good site to get started on it:

http://www.maximumcompression.com

It's not been updated in a while, but it's excellent.

If a ZIP file cannot be recovered by the normal recovery mechanisms inside your compression software, it's unlikely that it can be recovered. Ever. Download again, or resign yourself to it being lost. The amount of effort to recover a corrupt file is likely not worth it.

If you want recovery capabilities, don't use ZIP compression.

[Edvard]

@Edvard: Those were anomalous instances and not repeatable.
...

True, but I bet I could corrupt any Zip file real fast by unplugging my box while creating an archive

All kidding aside, WinZip's knowledge base describes a few ways that Zip files can be corrupted; accidents being far more common, but rogue archive software writing invalid or incomplete headers factor in as well.
http://kb.winzip.com/kb/entry/35/

[Innuendo]

The zip file structure has always been....fragile. Consider using rar instead as it will give the option to store recovery records with the archive that will give one a much better chance of archive repair should something go wrong.

[MilesAhead]

The zip file structure has always been....fragile. Consider using rar instead as it will give the option to store recovery records with the archive that will give one a much better chance of archive repair should something go wrong.

Are there any free ports of Linux lossless compression tools that may be robust on Windows?  I'm just curious.  A few searches didn't bring up anything germane.