Thumbnail size too small

Hello - When looking at a list of uploaded files in the Nextcloud web based environment I am finding the thumbnails are only 32x32 pixels. That is way too small.

Can anyone suggest where the setting is for changing that ?


It is not yet possible to adjust the preview generation, despite disabling it or force pre generation with the related app.

But there should be about 8 different sizes produced on demand, depending on where the thumb is shown, files app overview, details, gallery app etc.

Check your data/appdata_/previews folder, where all previews are stored, you should see also larger sizes there.

you can check and adjust values in three files:

(1) /var/www/nextcloud/config.php:

‘preview_max_x’ => 512,
‘preview_max_y’ => 512,
‘preview_max_scale_factor’ => 1,

(please find more information here)

(2) /var/www/nextcloud/apps/previewgenerator/lib/Command/Generate.php
(3) /var/www/nextcloud/apps/previewgenerator/lib/Command/PreGenerate.php

$s = 512;
while ($s <= $maxW || $s <= $maxH) {
$this->sizes[‘square’][] = $s;
$s *= 2;

$w = 512;
while ($w <= $maxW) {
$this->sizes[‘width’][] = $w;
$w *= 2;

$h = 512;
while ($h <= $maxH) {
$this->sizes[‘height’][] = $h;
$h *= 2;

(please find more information at

Adjust the values and ‘preview_max_scale_factor’ that should solve your issue?!
Cheers, Carsten


Thank you for writing back.

In my nextcloud config.php is found in /config/config.php

I have set

‘enable_previews’ => true,
‘preview_max_x’ => 2048,
‘preview_max_y’ => 2048,
‘preview_max_scale_factor’ => 10,

but they are being ignored…

The files you have mentioned Generate.php and PreGenerate.php do not exist in my Nextcloud 12 installation. So I searched out, found an app and installed and enabled previewgenerator.

I then ran from the command line sudo -u www-data /CM/data-drive/cloud_drive/public_html/occ preview:generate-all &

This allowed me to see the plugin scanning in action. So I was comfortable that it was in fact doing something (see image attached and also

However in the final analysis this had zero effect on the size of my super tiny 32x32 thumbnails (see image attached and also

Any thoughts?


Those are built into the files app and not user-editable. You could possibly raise an issue to change that, but in the interim if you’re browsing folders of pictures, switching to the gallery view will show them larger (as will selecting the photos show them in the details pane)

Hello and thanks Jason.

The gallery view is fine if all I want to do is view them and nothing more. Gallery offers no way to move resources to different folders etc… My goal is to be able to identify which images / files I want to move to a different folder and use the Files clipboard plugin to cut / paste them.

Unfortunately there’s no way to do this in Gallery and the thumbnails are too small to identify.

Seems like a drag and drop / cut and paste for images would be something everyone would be needing.

Am I missing some basic functionality here somewhere? Is there a drag / drop feature for images that I am simply not aware of ?


No, currently what you see is what we have. Thumbnail size options would be a great-to-have, feel free to raise as a feature request


I would also like to address your other idea of selecting the photos to show them in the details pane.

In my case I have perhaps 1000 photos in this one folder.

If the thumbnails were perhaps 125px I would know at a glance which folder I wished to paste them in. On the other hand, selecting one photo - viewing details - then another and so on will take infinitely longer to do do.



I have added these to the Issues link as you have suggested.