NC download/ sync speed over file system ~10MB/s, with browser 32MB/s. Why? And how to improve?

Nextcloud version: 25.0.12
Operating system and version: Raspberry Pi OS Bullseye
Hardware: Raspberry Pi 4 2GB
Apache version: Apache 2.4.56
PHP version: 7.4.33

The issue you are facing:

When I use the file system, i.e. Windows Explorer, to retrieve the contents of an approx. 1.5 GB virtual file from the server, I get a fluctuating transfer rate of between 5-13 Mb/s. If I do the same via the browser, I get a fairly constant transfer rate of approx. 32MB/s. Why is there such a big difference here? How can I achieve a higher transfer rate via Windows Explorer?

The output of your config.php file:

$CONFIG = array (
  'instanceid' => 'XXX',
  'passwordsalt' => 'XXX',
  'secret' => 'XXX',
  'trusted_domains' =>
  array (
    0 => 'XXX',
  'datadirectory' => 'XXX',
  'dbtype' => 'mysql',
  'version' => '',
  'overwrite.cli.url' => 'XXX',
  'dbname' => 'XXX',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'XXX',
  'dbpassword' => 'XXX',
  'installed' => true,
  'default_phone_region' => 'XXX',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'enable_email' => false,
  'maintenance' => false,
  'theme' => '',
  'loglevel' => 2,
  'has_rebuilt_cache' => true,

hi @nextcloudmeister welcome to the forum :handshake:

usually people comlain in opposite direction. “plain” file copy using SMB or other simple network protocol is in general faster than Nextcloud file operations. additionally I’m not aware of any way to access Nextcloud data other then through web server (browser/WebDAV/client)… issues related to simple file copy you better ask in Raspi community as this is more related to the underlying operating system than Nextcloud application.

and as the last hint: don’t temper with Nextcloud storage! “It’s best access files stored in Nextcloud through official interface e.g. WebDAV so the application can keep track of changes and offer functions like trashbin and versions. If you temper with Nextcloud’s storage the system might behave unexpected and data loss might occur.