# Electronic vs digital signature

An electronic signature is a legal idea: a person showing they agree, by drawing, typing or clicking. A digital signature is a technical one: maths over a file that shows it hasn't changed since it was signed. A good e-signature process uses both.

## Side by side

| | Electronic signature | Digital signature |
|---|---|---|
| What it is | Any sound, symbol or process a person uses to sign, with intent | A cryptographic value computed over the file with a private key |
| What it looks like | A drawn or typed name, a click on "I agree" | Usually nothing visible; a reader shows a signature panel or banner |
| What it shows | That a person meant to agree | That the file is the same as when it was signed, and which key signed it |
| What it doesn't show | That the file is unchanged afterwards | That a particular person meant to agree |
| Examples | Signing in Preview or Markup, an e-signature link | A certificate signature in Acrobat, a PAdES seal |

## Electronic signatures

In the US, the ESIGN Act and state UETA laws say a signature can't be refused just because it's electronic. The law cares about intent, not appearance. Your drawn signature in Preview counts, and so can a typed name, if you meant to sign.

The weakness is proof. A signature image on a PDF can be copied, and the PDF can be edited after signing. If someone later says "I never signed that", the image alone doesn't settle it. See [is an electronic signature legal](/guides/is-an-electronic-signature-legal) for how courts look at this.

## Digital signatures

A digital signature uses a key pair. The signer's software hashes the file and signs the hash with a private key. Anyone with the matching public key can check that the file hasn't changed by a single byte. Inside PDFs, the standard for this is PAdES, which we explain in [what is PAdES](/guides/what-is-pades).

A digital signature says which key signed, not which human meant to agree. A certificate links the key to a name, and how much that's worth depends on who issued the certificate and how they checked identity.

## You usually want both

The strong setup puts a person's electronic signature on the document, records each step around it (who got the link, when they opened it, when they signed), and then applies a digital signature to the finished file so any later change shows. That's how e-signature services work, docuinked included.

docuinked seals each completed PDF with a PAdES signature and an outside timestamp, and adds a certificate of completion and an [audit trail](/guides/audit-trail-explained). One honest limit: our seal certificate isn't on Adobe's trust list yet, so Acrobat names the signer as unknown, while its check that the file is unchanged still works. Anyone can check a file with our [free PDF checker](/tools/verify-pdf).

## How to add a digital signature yourself

Acrobat Reader can apply a certificate-based signature if you have a digital ID; look for the option to sign with a certificate or digital ID in its signing tools. Most people never need to. If you're signing a form that someone else asked for, a normal electronic signature is what they expect. For the everyday steps, see [how to sign a PDF](/guides/how-to-sign-a-pdf).

## Common questions

### Is a digital signature more valid than an electronic one?

Not by default. In the US, both can satisfy a signature requirement. A digital signature adds proof that the file hasn't changed, which helps if the document is ever disputed.

### Is a scanned handwritten signature an electronic signature?

Yes, if you put it there meaning to sign. It's an image like any other, so it carries the same weakness: it can be copied and the file edited around it.

### Why does Acrobat show a blue banner on some signed PDFs?

That banner comes from a digital signature in the file. Acrobat is reporting whether the file is unchanged since signing and whether it trusts the certificate that signed it.

### Do I need a certificate to sign a PDF electronically?

No. A certificate is only for digital signatures. Drawing or typing your signature in a free tool needs nothing extra.