What Is a Digital Signature? Digital vs. Electronic Signatures Explained

People use "electronic signature" and "digital signature" as if they mean the same thing. They don't. An electronic signature is about intent — a mark that shows you agreed. A digital signature is about cryptography — maths that proves a document has not changed since it was signed and ties it to a signer. Most online "sign a PDF" tools give you the first and quietly skip the second. Here is what each one actually is, how a digital signature works under the hood, and how to get the security people expect from a digital signature without wrestling with certificates.

What is an electronic signature?

An electronic signature (eSignature) is any electronic indication that a person intends to agree to the contents of a document. That covers a lot: typing your name at the bottom of an email, drawing your signature on a touchscreen, clicking an "I accept" button, or pasting an image of your handwritten signature onto a PDF. What matters legally is intent and attribution — that you meant to sign, and that the signature can be tied to you.

Electronic signatures are legally recognised almost everywhere: the US ESIGN Act and UETA, the EU eIDAS Regulation, and equivalent laws in 190+ countries all give them effect. For the vast majority of business documents — contracts, NDAs, offer letters, consent forms — a well-captured electronic signature is perfectly binding. Its weakness is evidential: a pasted image of a signature proves very little on its own, because anyone could have added it and the file can be edited afterwards without a trace.

What is a digital signature?

A digital signature is a specific, cryptographic kind of electronic signature. Instead of just placing a mark, it runs the document through maths that produces a unique fingerprint and binds that fingerprint to the signer, so that any later change to the document is detectable. It answers two questions an image signature cannot: has this document been altered since it was signed, and is it genuinely tied to this signer?

In the strict technical sense, a digital signature uses public-key cryptography (PKI): the signer holds a private key, the document is hashed, the hash is encrypted with that private key, and anyone can use the matching public key to verify it. That is the machinery behind certificate-based signatures and standards like the EU's advanced and qualified electronic signatures (AdES/QES). The practical point for a business, though, is the outcome: a digital signature makes a document tamper-evident and verifiable, not just marked.

Electronic vs. digital signature: the difference that matters

Think of it this way. An electronic signature is the equivalent of signing your name — it shows you agreed. A digital signature is the equivalent of signing your name and having a tamper-proof seal applied that would visibly break if anyone changed a single word afterwards. Every digital signature is an electronic signature; not every electronic signature is digital.

The differences that actually affect you: intent vs. integrity (an eSignature proves you meant to sign; a digital signature also proves the document is unchanged), evidence (a drawn image is weak evidence, a cryptographic seal is strong), and verification (a digital signature can be checked by a third party — a bank, a court, a counterparty — while a plain image cannot). For low-stakes internal paperwork the distinction rarely matters. For anything that could be disputed, audited, or relied on for money, it matters a lot.

How a digital signature actually works

At signing time, the document is run through a hash function such as SHA-256, which turns the entire file into a fixed-length string — a fingerprint. Change one character, one date, one pixel, and the fingerprint changes completely. That fingerprint is recorded and bound to the signed document along with who signed and when.

To verify later, you re-compute the fingerprint of the file you are holding and compare it to the value that was sealed at signing. Match means the document is the genuine, unaltered original; mismatch means it was edited after signing. There is no grey area and nothing to take on trust — the maths settles it. Certificate-based digital signatures add a trusted identity layer (the private key and certificate) on top of this integrity check.

Which one do you need?

For everyday agreements — service contracts, NDAs, quotes, employment letters, internal approvals — an electronic signature is legally enough. But you should still want the integrity half: the ability to prove the document was not changed after signing. That is exactly where most free "sign a PDF" tools leave you exposed, because they hand back a flat PDF with an image on it and no way to verify anything.

For higher-stakes documents — loans, leases, board resolutions, merchant agreements, anything involving money, identity, or likely disputes — you want the full strength of a digital signature: a tamper-evident seal, an audit trail of who signed and when, and ideally an identity check on the signer. The good news is you no longer have to choose between "easy eSignature" and "complex certificate software" to get it.

Get the security of a digital signature, the ease of an eSignature

PDF Verified captures an ordinary electronic signature — you draw, type or upload it in the browser, no certificates to install — and automatically backs it with the integrity guarantees of a digital signature. Every signed document is sealed with a SHA-256 cryptographic fingerprint, so any later change is detectable, and every page carries a QR code and a public verification link. Anyone — a bank, a partner, a court — can scan it and confirm, with no account, that the document is genuine and unaltered, who signed it, and when.

For sensitive agreements you can go further and require identity verification (a government ID plus a live selfie) before the document opens, binding a verified identity to the signature, and every completed document comes with an audit certificate that lays out the full chain of custody. In other words, you get the friction-free experience of an electronic signature with the tamper-evidence and verifiability people associate with a digital signature. Try it at pdfverified.com — your first document is $1.50, no subscription required.