PDF Signature Checker
CryptoInspect digital signature metadata embedded in a PDF with X.509 certificates. Verify signer identity and certificate chain without uploading your file.
About PDF Signature Checker
You cannot tell by eye whether a PDF contract truly carries a digital signature or whether its content was quietly altered after signing. This tool parses a PDF's internal signature structures locally in your browser, reading the digital signature dictionary, signer certificate details, and the byte range (ByteRange) the signature covers, helping you judge whether the document is digitally signed and whether the signature spans the whole file. The file is parsed entirely on your device with no upload, ideal for quickly verifying a contract or e-signed document before you accept it, so you avoid trusting a tampered or unsigned file. Tip: Bookmark this tool for quick access whenever you need to generate keys or hashes. All processing happens locally in your browser — no data upload, so it is safe to use with sensitive material.
How to Use
- Open the PDF Signature Checker tool page
- Enter or paste your data into the input area
- View the real-time results and use the copy button to get the output
Use Cases
- Verify contract signatures — Before accepting an e-signed PDF contract, confirm it actually contains a valid signature dictionary.
- Check for tampering — See whether the signature ByteRange covers the entire document to spot edits appended after signing.
- Inspect the signer — Read issuer and subject details from the signing certificate to confirm the signer's identity.
- Review files in bulk — Quickly tell which PDFs in a batch are signed and which are plain documents.
- Diagnose invalid signatures — Understand whether a reader's "signature invalid" warning stems from structure or alteration.
- Compliance review — Check that a batch of signed PDFs from a third party all contain valid signature dictionaries for regulatory auditing.
- Signature health check — Verify that a PDF's embedded certificate chain is structurally sound before long-term archival.
FAQ
Can this tool confirm a signature is definitively valid?
It parses and shows the signature structure, certificate info, and ByteRange, telling you whether the document is signed and whether the signature spans the file. Full validity also requires verifying the certificate trust chain and revocation status, which usually needs online CA/CRL/OCSP, so defer to a professional PDF reader's final verdict.
Why does ByteRange matter?
ByteRange defines the byte ranges the signature protects. If a signature covers only part of the content, or the document was appended after signing (incremental update), post-signing tampering may exist, and checking it surfaces that risk.
Are e-signatures and digital signatures the same?
Not exactly. An "electronic signature" broadly means any electronic intent to sign and may just be an image; a "digital signature" specifically means a cryptographic signature based on public-key crypto and certificates that verifies integrity and identity. This tool targets the latter.
What does it mean if no signature info appears?
Usually the PDF has no embedded digital signature at all and is a plain document or carries a handwritten-signature image. Image signatures offer no cryptographic tamper resistance and should not be taken as proof of trust.
Will my contract file be uploaded?
No. The PDF is parsed locally inside your browser and its content is sent to no server, suitable for sensitive contracts containing trade secrets or personal data.
Any browser compatibility requirements?
This tool works in all modern browsers (Chrome, Firefox, Edge, Safari). No plugins or extensions required.
Can I use it offline?
After initial load, most features work offline. The core logic runs entirely in your browser with no network dependency.
Comments
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