Newer versions of Microsoft Word (in particular, Office 365) will no longer open older .DOC files. If you want to convert these to the current supported .DOCX format (especially if you have a batch of files to convert), LibreOffice is a good option.
LibreOffice is free open-source software and you’ll get the benefit of doing everything on your computer. There are a lot of online services which advertise converting these files, but for anything personal or confidential I prefer keeping everything local.
Quick Background
As part of my effort to tidy up my digital life, I’ve been cleaning off and recycling old computers and consolidating a bunch of backup hard drives and disks. Among other gems I found a bunch of old .DOC files and learned that modern versions of Microsoft Word could not open them at all.
I assume this is for security protection reasons, perhaps to block against macros and other live code which were possible in those older formats. Unfortunately this can lead to “format rot” where you have perfectly valid archived files which are no longer usable.
For example, using Word for Mac (Office 365 version), I get this block when I try to open old .DOC files:
The link points to this support article: Error: [Filename] uses a file type that is blocked from opening in this version – Word for Mac.
On Windows (also Office 365 subscription version), it will open these files but in protected mode (meaning, no edits are possible):
Luckily if you’re on Windows you can adjust the settings (Trust Center | File Block Settings) to enable older files which you trust to be opened:
Finally, if you do have an Office 365 online subscription, these older .DOC files can be viewed. If you want to edit online, it will offer to convert to the newest format for you. This looks like the easiest option if you just have an occasional file you need to convert.
Installing LibreOffice
For anything more than the occasional file, LibreOffice is a good option for converting multiple files quickly.
To install, follow the LibreOffice installation instructions.
In my case on macOS I like to install things with Brew where possible, so my install step was simply:
$ brew cask install libreoffice libreoffice-language-pack
Open the LibreOffice app one time to make sure everything was installed and configured correctly.
Converting DOC to DOCX with LibreOffice
With LibreOffice installed, you can convert files two different ways. The first way is to open the .DOC file and then “save as” in the .DOCX format. I experimented with this on a few files and it works fine.
If you have several files to convert, you can use the command line. The location will depend on which platform you’re using, but in my case (macOS), it looks like the following.
First to make sure you have the right location, and to see the online help, try the following:
/Applications/LibreOffice.app/Contents/MacOS/soffice --help
In the help you’ll see the --convert-to and --outdir options which we’ll be using. A simple conversion of one file will look like this:
/Applications/LibreOffice.app/Contents/MacOS/soffice --headless --convert-to docx FILE.DOC
Converting a directory full of files is possible as well:
$ /Applications/LibreOffice.app/Contents/MacOS/soffice --headless --convert-to docx --outdir ~/Desktop/output ~/Desktop/convert/*.DOC
convert ~/Desktop/convert/BAZ.DOC -> ~/Desktop/output/BAZ.docx using filter : Office Open XML Text
convert ~/Desktop/convert/CATHY.DOC -> ~/Desktop/output/CATHY.docx using filter : Office Open XML Text
convert ~/Desktop/convert/FONTS.DOC -> /Users/brian/Desktop/output/FONTS.docx using filter : Office Open XML Text
convert ~/Desktop/convert/RESIGN.DOC -> ~/Desktop/output/RESIGN.docx using filter : Office Open XML Text
All of the DOCX files should now be fully working in Word. It’s possible that complicated documents may have some layout issues during conversion, but I think those should be relatively minor.