How to use it
- Drop the signed PDF here.
- Wait while signatures and timestamps are found and checked.
- Read the result for each signature.
- Use the details to decide whether to trust the document.
Digital signature vs signature image
A digital signature is cryptographic data embedded in the PDF. It is created with a certificate and a private key, and it covers the exact bytes of the document at the moment of signing. If anything in the signed part changes afterward, the signature no longer matches.
A signature image, such as a drawn or scanned signature placed on the page (for example with Sign PDF), is just a picture. It may be a valid electronic signature for many purposes, but it cannot be verified cryptographically. If the tool finds no digital signature, it says so.
What the check shows
For each signature or document timestamp, you see:
| Item | Meaning |
|---|---|
| Signer | The name in the signing certificate |
| Certificate issuer | Who issued the certificate, or self-signed if the signer created it themselves |
| Certificate validity | The certificate's start and end dates, with a note if it has expired since |
| Qualified certificate | Whether the certificate declares itself qualified under the EU eIDAS rules |
| Signing time | The time claimed by the signer's computer, and a trusted timestamp time if present |
| Signed content intact | Whether the document hash still matches: the core tamper check |
| Signature matches the key | Whether the signature was made with the certificate's key |
| Covers the whole file | Whether anything was added after this signature |
A summary line for each signature says whether the signed content is intact, whether something was appended later (normal for later signatures and timestamps, worth a look otherwise), or whether the content has changed.
What the check does not do
This is an informational check, not an official validation. It verifies the math: that the signature matches the certificate and that the signed bytes have not changed. It does not check:
- whether the certificate authority that issued the certificate is trusted, or appears on a trust list;
- whether the certificate was revoked before the signature was made;
- whether the person named in the certificate actually controls it.
A self-signed certificate can carry any name, so a mathematically valid signature from a self-signed certificate proves only that the document has not changed since someone signed it. For a binding validation, use a PDF reader that validates against trusted certificate lists, or ask the issuing organization.
Private verification
The file is analyzed entirely in your browser and is never uploaded. That makes it suitable for contracts, government documents and other signed files you should not share.
A worked example
You receive a signed contract PDF and want to make sure nobody edited it after signing. Drop it here. The tool finds two signatures: the other party's and a timestamp. For the first signature, Signed content intact: yes, Signature matches the key: yes, and Covers the whole file: no – 18 KB was added to the file afterward, with a note that a later signature or timestamp was added, which is normal. The second entry is the timestamp covering the whole file. If instead you saw Signed content intact: no, the document was changed after signing and you should ask for a fresh copy.
Frequently asked questions
How do I check if a PDF signature is valid?
Drop the PDF here. For each signature, check that the signed content is intact and the signature matches the key, then review who issued the certificate.
Why does it say the signature is valid but self-signed?
The math checks out, but the certificate was created by the signer, not a trusted authority, so the name in it is not independently confirmed.
Does this replace official validation?
No. It does not check trust lists or certificate revocation. Use it as an informational check.
Why was no signature found?
The PDF has no digital signature. A drawn or scanned signature image cannot be verified cryptographically.
Is my PDF uploaded?
No. Verification happens in your browser.
Last updated: November 12, 2026