If the link does not belong to your npub, then it would be impossible to delete. We only allow you to disassociate from the uploaded media if it is a duplicate, or delete the media if you own it.
Discussion
I sure use the account which I uploaded the image delete the image.
I know that
Please check that in the browser using the Developer Console and see the headers. We have x-owners-npub (or something like that) if it is properly authenticated when it was uploaded.
Thanks, will try and let you know when I am at home later
This is the info from Console
I meant for the media, not the webpage json request.
Request: No payload for this request.
Response: status:”error”, message: “ Delete failed: Media not found”
What I said was: check the headers of the file that you are trying to delete, and see if it has your npub listed as the owner.
Ok, seems not include any pubkey info
This means that it was uploaded unauthenticated. Which client did you use to upload?
#nostrmo
Hmm, I thought they already authenticated their uploads. Do you know who is the dev for that client?
Tells me it uses nip96 which requires authentication. That is strange. Can you DM me the file name so I can check?
The NIP96 upload file is here:
https://github.com/haorendashu/nostr_sdk/blob/master/lib/upload/nip96_uploader.dart
I upload a test file and try to delete it.
1. Upload success.
2. Download success.
3. It seems first time i try to delete at https://nostr.build/delete/ it tell me *delete success* .
4. But this file still can download.
5. And i try to delete this file again, it try me delete fail.
upload info:
file name: b89ad7e9d01d7002051847ac3762bb5b2191d9ae32b5df363d04545755892aa0.png
npub name: npub13jyr30u0x6uxzdcta0p2eh5dza0jhkglpp7mk3z7maej0ycamxgqw0y824
I tried using nostrmo from Mac desktop and was not able to detect authentication for the upload. I wonder if something is missing?
Have you change the image service to NIP96? If you select nostr.build upload service, it will try to use the old upload api.
The easiest way to verify if you fully own the upload is by checking media’s http headers. See examples for your file and mine. 
