Accessibility rules

[Kantonia]

Am I right that "Watermark" is the same as "alt text" or "caption" : A text shown in screenreaders for blind or visually impaired visitors of the site.

[BaconFries]

Am I right that "Watermark" is the same as "alt text" or "caption"

No a "Watermark" is used to protect the image against the likes of theft of the photo and protect copyright ownership. It can be text or a logo that is embedded (becomes part of it) into the photo. The alt tag is then applied to the photo itself for as you mentioned accessibility issues and for screen readers to aid visually impaired users when the mouse is over.

[Kantonia]

And how do I add alt text to my Photos?

[BaconFries]

And how do I add alt text to my Photos?

The alt tag of an image/photo is set via the 'Description' property of the image/photo.

[Kantonia]

Using a German language file, I do not find "Description" nor the German equivalent "Beschreibung". I send you a screenshot so that you can tell me which line it is:

[Pablo]

'Description' is 'Anderer text"

[AliGW]

I always thought it was known as ALT text (short for alternative).

[BaconFries]

@ AliGW it is but in this instance the OP (Kantonia) is using the German version of the software so that it shows 'Description' is 'Anderer text" and when used it gets applied to the "alt" as well.

[AliGW]

Yes, I understood that, thanks.

[Kantonia]

Pablo, thank you!