der Leser
reader
A person who reads a text, for example in a book, a newspaper, or on a website.
Der Autor erhielt viele positive Rückmeldungen von seinen Lesern.
The author received a lot of positive feedback from his readers.

reader
Loading your saved state.
reader
A person who reads a text, for example in a book, a newspaper, or on a website.
Der Autor erhielt viele positive Rückmeldungen von seinen Lesern.
The author received a lot of positive feedback from his readers.

The word 'Leser' (reader) is derived directly from the verb 'lesen' (to read). The ending '-er' refers to a person or device that performs the action of the verb.
Ein guter Autor versteht, was seine Leser erwarten.
A good author understands what their readers expect.
You can tell from context whether a person or a device is meant. Words like 'Buch' (book), 'Zeitung' (newspaper), or 'Autor' (author) point to the person. Technical terms like 'Karte' (card), 'CD' (CD), or 'Daten' (data) point to the device.
Bitte stecken Sie Ihre Bankkarte in den Leser.
Please insert your bank card into the reader.
For the person who reads, there are typical collocations such as 'ein begeisterter Leser' (an enthusiastic reader), 'ein treuer Leser' (a loyal reader), or 'Leser ansprechen' (to appeal to readers). The word 'Leserbrief' (letter to the editor) as a response to an article is also a common combination.
Als begeisterter Leser kauft er jede Woche mehrere Bücher.
As an enthusiastic reader, he buys several books every week.
The meaning as a person who professionally reviews texts for a publishing house is specialized language from the book and media industry. This meaning is rare in everyday language.
Das Manuskript wurde von drei verschiedenen Lesern abgelehnt.
The manuscript was rejected by three different readers.
user
'der Nutzer' and 'der Leser' can both refer to people on the internet or in an app. The difference lies in the focus. A 'Nutzer' uses a service, product, or technical system. They click, search, write, or configure something. A 'Leser' mainly reads a text, for example an article, a book, or a website. The words can be confused when someone visits a website. If the person is only reading the text, 'Leser' is more precise. If they are using the site as a service or system, 'Nutzer' fits better.

Nach dem Artikel schrieb ein Leser einen langen Kommentar.
After the article, a reader wrote a long comment.
Der Nutzer kann in der App seine Daten selbst ändern.
The user can change their data in the app themselves.