# PDF Signature Detector

URL: https://phishdestroy.io/developer-tools/pdf-signature-checker
Category: Files & pages
Where it runs: Runs locally (nothing you enter is uploaded)

Choose a PDF to see whether it contains digital signature markers (/ByteRange and /Sig) and any signer name, reason and location stored with them. It does not validate the signature or the certificate.

## Example input

A digitally signed PDF

```
A PDF signed with a digital certificate, chosen with Upload PDF
```

Shows how many signature markers and ByteRange entries the file has and any /Name, /Reason and /Location text; an unsigned PDF shows No digital signatures found in this PDF.

## FAQ

### Does it verify that a signature is valid?

No. It only searches the file for /Sig and /ByteRange markers and literal /Name, /Reason and /Location strings; it does not check the certificate, the signer's identity or whether the document changed after signing. Use Adobe Acrobat Reader or pdfsig to validate.

### Can the result be wrong?

Yes. An empty signature field also contains /Sig, so an unsigned form can show markers, and one signature usually produces several /Sig matches; the ByteRange count is the closer estimate. A signature image pasted onto an invoice is not a digital signature and is not detected.

### Is the PDF uploaded?

No. The file is read in your browser and never leaves it. The whole file is loaded into memory, so very large PDFs can be slow.

## Related tools

- [File Type Sniffer](https://phishdestroy.io/developer-tools/file-type-sniffer)
- [File Hash Calculator](https://phishdestroy.io/developer-tools/file-hash)
- [X.509 Certificate Decoder](https://phishdestroy.io/developer-tools/x509-decoder)
- [HTML Attachment Analyzer](https://phishdestroy.io/developer-tools/html-attachment-analyzer)
- [Base64 File Converter](https://phishdestroy.io/developer-tools/base64-file-converter)

All tools: https://phishdestroy.io/developer-tools