Power BI file size huge increase in file size

[darrellkilian]

I've just used the latest version of Power BI desktop (2.144.1155.0 64-bit June 2025) to open a report pbix file, make a minor text change and save, and the file size increased from 164 KB to 3,800 KB - a huge increase for no reason.
The file is a report only - it connects to a semantic model in the cloud, so should not contain any data.

Has something changed that I should expect such an increase. It seems really odd.

I tried it with more than one file, and a colleague did as well, wit hthe same huge increase in file size.

Help. what is happening?

[darrellkilian · Accepted solution]

After a screen sharing session with Microsoft support, they identified this as an issue in recent release, that large built in template json files were being embedded in the pbix file when a file is edited and saved. They said their engineers are looking at this. The problem does no harm other than increasing your file sizes. Should hopefull be fixed soon. They said I could use an older version of PBI desktop. I installed the previous version which did not have the same issue.

Thanks to @OwenAuger, @v-dineshya and @danextian for your help.

[v-dineshya]

Hi @darrellkilian ,

Thank you for reaching out to the Microsoft Community Forum.

Please try below things to fix the issue.

1. Avoid Built-In Themes, switch to a custom theme or the default theme before saving the file. This may prevent the large theme files from being embedded.

2. The issue seems to be specific to reports connected to cloud semantic models. Test with imported models to see if the behavior persists.

3. Use version control or file comparison tools to track what changes are causing size increases.

4. Save the file as Template file (.PBIT) and rebuild if needed. File > Export > Power BI template (.pbit) saves only metadata, no data or built-in themes.

File size will be drastically reduced, and you can reuse/rebuild if necessary.

5. It's may be a behavioral change due to latest updated version. Revert to an older version of Power BI Desktop, If this behavior is breaking workflows or automation, Uninstall the current version and download earlier version.

Please refer below link, to download the Power bi desktop previous versions.

https://learn.microsoft.com/en-us/power-bi/fundamentals/desktop-latest-update-archive?tabs=powerbi-d...

Please refer community thread.

Solved: increase in PBIX file size Issue due to Change in ... - Microsoft Fabric Community

I hope this information helps. Please do let us know if you have any further queries.

Regards,

Dinesh

[OwenAuger]

Interesting...I tried reproducing this at my end but couldn't get the file size above 5 KB.

I would recommend opening a copy of the pbix as a zip file (copy & rename as .zip if needed), then extract to a folder and examine files in all subfolders.

Other files that might creep into a pbix could include images or themes, though not sure how that would have happened in your case. 🤔

[darrellkilian]

Thanks for the suggestion @OwenAuger , the culprits are two built in theme files:

Bloom.json (3 MB) and Tidal.json (1MB), both including huge embedded base 34 png images.

Seems you can't uninstall built in themes, though.

Trying to reinstall PBI.

Any other thoughts?

in the zip file in \Report\StaticResources\SharedResources\BuiltInThemes

[OwenAuger]

Thanks for the update, and glad you have found the problem 🙂

I don't know off the top of my head but some old posts mention BuiltInThemes being present in pbit format (not sure if a pbit was involved at any stage).

I also wonder if the new Organizational Themes feature has anything to do with it (if that has been set up on your tenant).

[darrellkilian]

Hi @OwenAuger , thank for your reply. There were a couple of custom visuals, not actually used in the report, so I removed them, and saved. This reduced the size by a few KBs, but still over 3000 KB, whereas the original was a few hundred KB.

I then tried crating a blank report, linked to an online semantic model, but only containing a single text box. I saved this to produce a 5 KB file. I closed PBI, oened the 5KB file again, added a full stop in the text box and save, and the file size jumped from 5KB to over 3000 KB.

Interestingly, when I created a new simple report with internal semantic model and simple data imported from spreadsheet, then save, reopen add text box edit and close several times, the file size does nto go up. Only when connected to a semantic model published to the PBI service.
Is PBI doing anything different. PErhaps I should reinstall it?

[danextian]

I then tried crating a blank report, linked to an online semantic model, but only containing a single text box.

This answers the question. When you open a pbix linked to a semantic model and tries to save it, it creates some sort of a cached copy of the semantic model (for the lack of a better term). I've observed this even for those that are just simply opened and then saved. Once published and then re-downloaded, the size reverts back. 

[danextian]

If the culprit isn't the custom visuals, what is that minotor text change?

[darrellkilian]

Minor text change was just a single word in a text box.

Then when I experimented, with other files, I just removed then readded a full stop and saved, and immedately the file size jumped. This happened to a colleague as well.

[OwenAuger]

Hi @darrellkilian 

It's possible some custom visuals may have been inadvertently included in the PBIX (even if no tiles associated with those visuals exist in the report).

You can verify this by opening the PBIX as a ZIP file and examining any files under Report\CustomVisuals.

If this happens to be the case, remove the offending visuals here:

Did that happen to be the issue?