Archiving indd files, interest in the idml format?

[oups_]

Hello everyone,

I am setting up an archiving NAS containing all completed work.
I am wondering about the viability of the files in the long term (and after multiple Adobe updates), especially the .indd files
Can opening .indd files created with a much older version of inDesign cause problems?
If so, what kind of problems?
How can I avoid it?

On old files, I have already noticed that inDesign offers to "convert" the file to open it with the latest version of inDesign, but I do not know if this is a reliable solution or if some files risk becoming completely unusable despite everything.

Does systematically saving a copy of my .indd files in .idml format have any interest?

I do not understand these .idml files and their use, but I have read that .idml files have better compatibility between versions.

Maybe I'm asking too many questions and a simple .indd record is enough, but I'd like to be sure to do something clean and sustainable.

Thanks 🙂

[Eugene Tyson · Accepted solution]

InDesign’s native .indd files are version specific. That means a file created in a newer version may need conversion to open in an older version and that conversion isn’t always perfect. You might lose some advanced settings or experience layout shifts when InDesign “updates” the file for compatibility. 

Saving a copy as an .idml file creates a “recipe” of your document in an XML-based format. This text-based snapshot is more backward compatible (usable with versions as far back as CS4) and can often be imported even when the original .indd might throw a fit. However, note that .idml files strip out some of the embedded cache data, like image previews, to keep the file lean. So while they’re great for ensuring your layout’s core data is preserved, you should still archive your complete asset package (including images, fonts, and the final PDF for reference).

Consider saving both the .indd and a corresponding .idml file. This dual approach protects you from future Adobe updates and potential conversion issues. The .indd preserves all the original design data (at the cost of larger file sizes and potential compatibility quirks), while the .idml serves as a more “future-proof” backup that can be re-opened in InDesign or even other layout tools if needed.

Archiving both formats, along with images/fonts/pdfs etc gives you a safety net against the evolving nature of software.

[Robert at ID-Tasker]

@oups_

For archiving purpose - you should use File / Package and check all options - copying images, IDML / PDF generation, Fonts - but not all fonts will be automatically copied.

Then, you can just ZIP / RAR whole folder - optionally, split it into pieces with extra recovery information. 

IDMLing is also a way to fix corrupted files. 

[Robert at ID-Tasker]

@oups_

And IDML is a ZIP package - you can add ".zip" at the end - or rename - and see inside yourself.

[Peter Spier]

Can opening .indd files created with a much older version of inDesign cause problems?
If so, what kind of problems?

By oups_

Opening files in a different version (newer or older) can cause text to reflow due to changes in the text engines from version to version, but this reflow may not happen opeing in a newer version until you do some sort of operation that touched the text, and in a long doc this can cause surprises that you don't see right away.

As @Eugene Tyson going through .idml to open in an older version will also strip out any features used in the file that are not supported in the older version.

How can I avoid it?

You can't.

[oups_]

Thanks a lot for the clarification.
When I package my file, I see that an indd file is also generated, but it weighs 28.3MB while my original working file weighs 69.7MB.
How can it have so much weight loss, have I lost important data? I don't see any obvious difference when opening the files but I still wonder.
Can I keep only this Package folder in my archives ? And delete my original folder ?

I'm talking about the indd file generated during assembly, not the idml file (which is obviously lighter)

Have a nice day

[Eugene Tyson]

Your working file accumulates a lot of temporary data over time, such as undo history, saved previews, and other metadata that is no longer necessary.

When InDesign creates the packaged .indd, it strips out this extra information, resulting in a smaller file size.

InDesign stores previews of linked images, but during packaging, these previews may be regenerated in a more optimised way, or older previews removed etc.

This can slightly reduce the file size without affecting the quality of your actual linked images.

Your working file may include automatic recovery data in case of crashes.
The packaged file does not include this, making it smaller.

File Structure Optimisation

Over time, an indd file can bloat due to repeated saves and edits, but packaging the file essentially "rebuilds" it cleanly, making it more compact.

You haven't lost any essential content. The document itself, including all layouts, styles, links, and settings, remains intact. The weight loss is due to the removal of unnecessary data rather than anything that affects your design.

Can You Delete Your Original Folder?
If you work exclusively with linked images, your Packaged Folder (which contains the new .indd, Links, and Document Fonts) is usually safe to keep as your archive.

If you think you might need access to previous versions, backups, or file history, then keeping the original file is a good idea.
If you used embedded images in the original file, check if they still appear in the packaged version before deleting anything.

If disk space isn’t an issue, keep the original for a while and work with the packaged version to confirm that everything is intact. Once you’re confident, you can archive just the packaged folder.

[Robert at ID-Tasker]

@oups_

You're welcome. 

When you do just Save - Ctrl+S - to speed up things, InDesign is adding Undo History - all the steps you've done recently. 

Unfortunately, this Undo History isn't available when you close your document - but remains as part of your file. 

Over time, it can be more than the necessary contents of the file - and can lead to corruption.

You can experience this corruption "instantly" - when you won't be able to open your file correctly or at all - or "delayed" - InDesign will crash when you try to move something on some page. 

That's why it's a good idea to do Save As with a new name at the end of the day - or every few days if you don't work too much on your file.

IDMLing strips everything to a "bare metal" - no Undo History, no previews, etc. - and fully rewritte and reorganise contents of your file.