What is a presigned URL?
By Mark Boreland ·
In short
- A presigned URL is a temporary link, cryptographically signed, that grants access to a specific file in cloud storage for a limited time.
- It lets a private bucket serve a file without being made public.
- It is part of how a modern host shares files securely without exposing your whole storage.
A presigned URL is a link that carries its own permission. Cloud storage like Cloudflare R2 or Amazon S3 keeps files in private buckets that are not openable by default. To let someone access one file, the system generates a URL signed with a secret key and stamped with an expiry. Anyone holding that URL can fetch that one file until it expires, and nothing else. It is a way to grant narrow, temporary access without ever making the bucket public.
This is the quiet plumbing behind secure sharing. When you share a PDF as a link, the file sits in private storage, and access is handed out through signed URLs rather than by leaving the whole bucket open to the world. The signature means the link cannot be forged, and the expiry means a leaked link does not grant access forever. It is the same mechanism large platforms use to serve private uploads safely.
For you none of this is visible, which is the goal. You get a clean, friendly link, while the signing and expiry happen underneath. The concept connects directly to self-destructing links, where you choose how long access lasts. Hosting is free to start and the pricing page covers higher limits. The takeaway is that a good host shares files without ever exposing the storage they live in.
Related terms
Frequently asked questions
Is the share link I get a presigned URL?
Your friendly nudgehost.com link sits in front of the storage. Access to the underlying file is granted through signed, expiring URLs so the storage stays private.
Why not just make the storage public?
A public bucket exposes everything in it. Signed URLs grant access to one file at a time for a limited window, which is far safer.
Does the signature stop someone guessing my link?
The cryptographic signature cannot be forged, so a URL cannot be fabricated. Combined with expiry, that keeps access tightly scoped.
Related tools
Other things you can do on NudgeHost.
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