Verify signed documents
Check who signed a PDF, how each person confirmed who they are, and whether anything changed since. Free, with no account. Your file never leaves your device.
Sovrasign Verify · open source. It checks documents signed with Sovrasign.
How to check a document
- Open the verifier.
- Choose the signed PDF, or drop it on the page.
- Read the result: who signed, how each person was verified, when, and whether the document is intact.
The check runs entirely in your browser. The file is read on your device and is not uploaded.
What the verifier checks
- Every signature is intact. Each one still matches the bytes it signed.
- Nothing was added after the last signature. Any change saved afterwards, even a small one, makes the document fail.
- Each step is exactly one person's action. The verifier replays the document layer by layer: each signer could only fill in their own fields and add their own signature. The terms the sender sealed, other people's fields and earlier steps cannot change.
- What you see is what was signed. The verifier redraws each signature box and field value from the recorded data and compares them with what the PDF shows, so a box cannot display another name.
- Each identity is genuine. A signer verified with Google, Microsoft or Apple carries a statement signed by Google, Microsoft or Apple, tied to that one signature and that one document. The verifier only accepts the providers' own published keys.
- The record of steps is complete. Each entry is linked to the one before and signed by a participant.
What it cannot tell you
- Whether the provider's account was the person's own. If someone took over a signer's Google, Microsoft or Apple account, they could sign as that person. The identity is as strong as the account behind it.
- A drawn signature proves nothing by itself. The proof is the verified identity printed next to it. The drawing is checked only to make sure it is pen strokes inside its box.
- The exact time, without a timestamp. A signature without a trusted timestamp carries the signer's device time. Paid plans add one to every signature; on Free, one timestamp covers the whole document and bounds its signers' times.
- Documents from other services. It checks documents signed with Sovrasign. Other vendors' signed PDFs follow other rules.
- The certificate of completion. That page is a readable summary, not proof. The proof is the PDF itself.
Open by design: check it yourself
The verifier and a description of the document format are open source under the MIT or Apache-2.0 license, with test vectors that anyone can use to test their own tools.
It will also be published on independent hosting, so checking a document never depends on our servers. Coming