Possible to turn off all file thumbnail generation?

I've turned off caching of thumbnails in Windows 10 so that File Explorer only displays the icons associated with a file type (I don't want Thumbs.dbs created all over the place, as well as it being an improvement to privacy). Unfortunately, this also means no thumbnail generation at all in File Explorer (according to my experience and searches). Edit: It's possible to just turn off the caching and still have thumbnail generation (via Group Policy Edit).

I recently discovered Icaros and would like to use it as my thumbnail generator due to it functioning even without a cache (though I do plan to whitelist some folders). Opus can generate without caching too, but it lacks some features and support for files that make Icaros the better choice for me. If I could disable Opus from generating thumbnails, it'd simplify things by being able to assume any that are seen are of Icaros' doing. The problem is, I can't find a way to do so.

Is it possible to turn off all thumbnail generation? For example with Icaros inactive, some MKVs I have display will still display a thumbnail, whereas others will not: when I quickly compared these, the videos inside didn't differ much other than by bit depth, 8 vs 10 (thumbnails vs no thumbnails) - Edit: File Explorer behaves the same way. When I activate Icaros, the thumbnails that Opus was generating get replaced with those by Icaros (hopefully Opus isn't doubly doing the work in the background).

I've tried disabling all the plugins via Preferences, but Opus keeps generating thumbnails. If I could disable image thumbnails too, Icaros could handle their generation as well (from what it looks like, but it's hard to tell if image thumbnails are getting replaced -- unlike videos which have different frames generated as their thumbnails).

Ideally, Icaros could handle all thumbnail generation and caching, and Opus would do nothing but display what Icaros has requested for generation.


- Directory Opus v12.23.3 Beta x64 Build 7752
- Windows 10 v20H2 OS Build 19042.870

You can disable video thumbnail generation by configuring the Movie plugin. (Prefs / Viewers / Plugins)

It doesn't seem to help. I already had the Movie plugin's Generate thumbnails option disabled, and disabling the whole plugin and restarting Opus makes no difference either. Is it possible that something else could be generating the thumbnails and Opus reading them, and how could I tell?

I'm not sure if this would help, but, here's a screenshot from ShellExView:

Icaros is disabled via its software so that's why it's missing. All the extensions in the screenshot are considered as by Microsoft according to ShellExView, so it doesn't look like anything I would have installed is interfering.

Out of interest, I enabled the Movie plugin's Generate thumbnails option, and it doesn't appear to change anything (the MKVs without thumbnails remain without any). Maybe the feature relies upon my Windows system not having its thumbnail caching disabled?

If the Movie plugin isn't generating thumbnails, Opus will ask Windows to generate them. What happens should be the same as what happens in Explorer in that case.

So I've spent some time testing this and it looks like the Movie plugin isn't behaving as expected; it's not possible to disable video thumbnail generation. Here's a video (explained below):

As seen in the Preferences, Opus has the Movie plugin disabled and too its option to generate thumbnails. Opus' thumbnail caching is disabled as well. If I've understood you correctly, in this scenario, it should be defaulting to what File Explorer displays.

After refreshing File Explorer and Opus to show they both display thumbnails, I disable thumbnails system-wide (turns out it's possible to only disable the caching, without disabling generation). Maybe this doesn't turn off generation? only "displaying", as is the wording?

At this stage, and with Opus restarted, I'd expect both file managers to be incapable of displaying thumbnails: true of File Explorer, but Opus continues to do so.

It appears it isn't possible to disable video thumbnails in Opus, which is fine, I can live with it, but it does seem to indicate that something may be wrong with the plugin.

I have a similar video regarding the slowness observed, that I'll make a new post for.


Those group policy settings don't stop the shell from generating thumbnails. They probably just tell Explorer to not display thumbnails. They don't have any effect on other software, or block the shell's thumbnailing APIs from working.

You'd probably have to find and disable the thumbnailers in the registry to completely disable them.

I'm not sure I understand what you're aiming to achieve, though. If the aim is to use Icaros to generate thumbnails then you need the shell's thumbnailing system to remain working, since Icaros is accessed through that.

That makes sense if true. I was just attempting to disable Opus from displaying any thumbnails so I could be sure what I'm seeing is the effect of Icaros. I could then know that the whitelisted directories in Icaros are working as intended etc. I'd also have the best of both worlds: no slowdown from generating thumbnails in directories I don't care about, and only see those I've designated Icaros to cache/generate for my music library etc. I was trying to find a way, but as you say, if I did manage to stop Opus from showing thumbnails, it'd probably also stop Icaros.

Would it be technically possible for Opus to request nothing of the system's thumbnail generator, and only display those that Icaros has requested?

If Opus didn't display any thumbnails, it wouldn't display any Icaros thumbnails.

No, Icaros is a thumbnailer shell extension. If you disabled shell thumbnails, you'd disable Icaros thumbnails, because they come via the shell's thumbnail system.

(It might be possible to write an Opus plugin which talks to Icaros's COM component directly, and then somehow disable the shell from generating thumbnails, but you'd need to write C++ code for that, and I'm not sure it would gain you much. The shell thumbnail system isn't something you really want to disable.)

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