google apps engine - can a blob stored in the blobstore be accessed by other apps?

Question

Are there some kind of permissions inside google apps engine that will regulate the access to blobstore data once known the blobkey?
in other words is it safe to share blobkeys?

Answer 1

No it can not. Just double-checked it in one of my apps and the second app can not find a blob via a key created by first app.

Answer 2

Google is moving away from the blobstore. Now you can use cloudstorage with free quota for the appid default bucket.

All files in cloudstorage can be made public.

You can not use the blobkey to share blobfiles. You always need a handler to serve (read) blobfiles or make images public using a serving_url. If you use a handler you control the access.