Signatures you can prove.

The audit trail, in plain English

When a document goes through eSignSimple, we keep a running log of what happened to it: when it was sent, when each signer opened it, when they signed, and when it was completed and downloaded. Each entry carries a timestamp, the IP address the action came from and basic device and browser details. It is the digital version of a witness who wrote down who came in, when, and what they did.

Why this matters: in a dispute, the question is rarely whether a squiggle looks like someone's handwriting. It is whether that person actually took the action. An audit trail showing that the signing link went to their email address, was opened from a particular device, and was followed by a signature a few minutes later is far more persuasive than an image of a name. When the document is complete, we summarise that trail in a certificate of completion that travels with the signed PDF.

The SHA-256 fingerprint and the verify page

When the last signer finishes, we calculate a SHA-256 hash of the final PDF. Think of it as a fingerprint made from every byte of the file. Change a single character, a date, or even invisible metadata, and the fingerprint comes out completely different. There is no practical way to alter a document and keep the same fingerprint.

Anyone can check a document on our public /verify page. You drop in the PDF, your browser computes its fingerprint, and we tell you whether it matches a document completed through eSignSimple. That means the other party, their lawyer, or a court does not have to take our word or yours for it; they can check the file themselves. We like evidence that anyone can test, not evidence that depends on trusting a vendor.

Which tools run in your browser, and which use our servers?

The Fill PDF tool and the signature generator do all their work on your device. You need a free account to open them, but once a tool is loaded the PDF is filled and saved in your browser tab, and the signature image is drawn and exported locally. Those files are not uploaded to our servers, so there is nothing for us to store, leak or be asked to hand over.

Sign PDF works differently, on purpose. When you sign a document yourself, it is uploaded and stored encrypted like any other document, signed in the same flow your signers use, and kept in your Documents with an audit trail and a certificate of completion. That gives you evidence of when you signed, and a SHA-256 fingerprint of the result that anyone can check on the verify page. The trade-off is that a self-signed document counts toward your plan's monthly documents. If a task does not need a server, we do not use one; where the server adds proof, we say so.

What we store, and what we do not

For documents sent through eSignSimple, we store what is needed to get them signed and prove it: the PDF itself, the names and email addresses of signers, the audit events described above and your account email. Documents are kept until you, the sender, delete them, and the audit data lives with the document.

We do not store passwords ourselves. You sign in with Google, or with an email address and password that is handled by Firebase Authentication, Google's sign-in service, so there is no password database on our side to leak. We do not store files from the in-browser tools, Fill PDF and the signature generator. Documents you upload to send for signature, whether PDF or Word, are stored encrypted, and Word files are converted to PDF on our own server rather than sent to a third-party converter. We do not sell data or use your documents for anything other than delivering the service. Our site uses Google Analytics to understand traffic, which is described in the privacy policy.

Our take on “military-grade” security marketing

You will see e-signature sites promise “military-grade” or “bank-level” encryption. It is marketing language, not a standard. It usually means AES-256, which is excellent and also what nearly every modern service uses. It tells you nothing about how access is controlled, how evidence is kept or what happens when something goes wrong.

We would rather describe what we actually do and let you judge. We use modern encryption in transit and at rest, keep a tamper-evident trail, and give you a fingerprint you can verify without us. We are an early-access service and we do not currently hold formal security certifications; we will not imply otherwise. If your organisation requires a specific certification before adopting a tool, tell us, and we will be straightforward about where we stand.

How do you know the right person signed?

Every signer reaches the document through a personal link sent to their email address. Opening that link and completing the signature is what ties the signature to the person: it shows the action came from someone with access to that inbox, and the audit trail records when it happened, from which IP address and on which device and browser. For the vast majority of everyday agreements, such as freelance contracts, NDAs, leases and consent forms, email-based identification plus a full trail is the accepted standard for a simple electronic signature.

It has limits, and we would rather you know them. We do not offer SMS codes, ID document checks or knowledge-based questions, so we cannot prove that the person holding the inbox is who they say they are. If a signer shares their email account, or forwards the link, the trail will show what happened but it cannot stop it. When the stakes justify it, add your own checks: confirm the email address with the person by phone before you send, ask them to reply to the completion email, and look at the audit trail for anything unexpected, such as a signature from a country where the signer has never been.

If a document legally needs a higher level of identity assurance, for example an advanced or qualified signature in an EU regulated process, eSignSimple is the wrong tool for that document. Our legality guides note where that tends to apply.

What happens if someone edits a signed PDF?

Here is a concrete example. A tenant receives the completed lease, opens it in a PDF editor and changes the monthly rent from 1,450 to 1,250. The file still looks signed: the signatures, the certificate page and the dates are all there. But when the landlord drops that file onto our verify page, its SHA-256 fingerprint no longer matches the one we recorded at completion, and the check fails. The landlord then downloads the original from their account, which does match, and the edit is obvious.

Two practical points follow. First, keep the file exactly as you downloaded it. Re-saving it in another app, compressing it, merging it with other files or printing it to PDF all change the bytes, and therefore the fingerprint, even if nothing visible changed. Store the original and send copies of it. Second, a failed check is a prompt to compare files, not proof of fraud on its own. The original download, the certificate page and the audit trail together tell you what the signed version said.

What you can do to keep your account and documents safe

Most real-world problems start outside the signing tool. Your eSignSimple account is only as strong as the way you sign in, so turn on two-step verification for the Google account you use, or choose a long, unique password if you sign in with email. Check signer email addresses before you press send; a typo sends a confidential document to a stranger, and the fastest fix is to void it straight away.

If you use the REST API, keep API keys on your server or in a secrets manager, never in a website's front-end code or a shared spreadsheet. We show a key once and store only a hash of it, and you can revoke a key in settings at any time; requests using it stop working immediately. Verify the signature on every webhook before you act on it.

Finally, decide how long you need documents. You can delete a document whenever you want, and you can delete your whole account from settings. Deletion is permanent, so download the signed PDFs you need to keep first. The certificate of completion is a page inside the PDF, so the evidence travels with your copy.