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I'd like to compare two files under Windows, each about 1Gb in size.
I tried Total Commander and WinMerge and both ended with Out of memory error.
I'm running Vista Home Premium 64bit with 8GB of RAM so memory should not be an issue here...

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10 Answers 10

What about just using fc or comp?

Both are included in Windows and should have no problems handling large files. In fact, 1 GiB is actually a pretty small file.

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fc works fine with such large files indeed. Its comparison algorithm is a bit sloppy though. – tricasse May 11 '13 at 22:30

I use Beyond Compare for this. It is a very good tool for file comparison and directory synchronization (although it is not free :-(

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It is very good value for the price and "A single user license covers one person using BC on any number of computers" – stukelly Sep 3 '09 at 21:15

Try ExamDiff (Pro).

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For just comparing two text files in a graphical way the free version ExamDiff seems to be also a candidate. – Robert Feb 25 at 16:46

I use HashTab, worked fine for 1 GB files the last time I needed them and it's free.

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It looks like they are both 32-bit apps, so even on a 64-bit platform they are bound to a 2GB max memory usage limit. Though, you would think they would have another way of handling this, such as paging the extra data.

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Yep, I can't believe they are loading whole files into memory... – Piotr Dobrogost Sep 3 '09 at 13:10

Try a checksum comparison tool that uses MD5 or SHA1. I use digestIT 2004.

If you are just trying to diff, you could try a command line diff tool or DiffUtils for Windows. Textpad also has a comparison tool integrated it the files are text.

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If you want to find the differences rather than simply find out if the files are the same (via a checksum) then you could split the files first and then try a file comparison.
7-Zip File Manager will split files into 650Mb chunks (File > Split file...) which should then open in DiffMerge

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+1 Nice workaround. – Umber Ferrule Oct 8 '09 at 10:04
Did you know TC also splits files? File > Split File... – Assad Ebrahim Dec 17 '12 at 7:13

So, which one work for you finally?

I use ExamDiff but I am not sure if it will work for ~1GB files.

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i use Hex Workshop for comparing large files at hex level.. sure, it's not free, but it's worth every penny. there's plenty o hex editors, hex calculators, file comparison,etc. but this is one of those cases where the whole is much more than the sum of it's parts

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My (ASCII) files were each about 1.2 GB.

I tried:

  • NotePad++
  • MultiEdit
  • Beyond Compare 3
  • ExamDiff Pro
  • DiffMerge
  • WinMerge and they all failed (couldn't load the file or crashed)

The one that worked for me at the end was ... PilotEdit x64 6.2.0.

It took some time to load each file and even more to do the comparison, but once it was done, it worked perfectly fine and just the way I had seen it in MultiEdit and NotePad++ before. Jumped between diff blocks, etc.

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It only worked because it was a 64-bit process. The other options when configured right would have worked. – Ramhound May 10 '13 at 3:17

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