Which plan includes the API?

The REST API and embedded signing are part of Pro and Enterprise. Webhooks start on Plus, so you can react to events from envelopes your team sends by hand.

Is API usage billed separately?

No. Envelopes created through the API count in the same monthly quota as envelopes sent from the app, 2,000 a month on Pro. There is no separate API product and no price per call.

How do I authenticate?

Create an API key in the developer settings of your team and send it as a Bearer token in the Authorization header. Only a hash of the key is stored, so the full key is shown once. Keys can be revoked at any time.

How do I know a webhook really comes from you?

Every delivery carries a signature header with a timestamp and an HMAC SHA-256 of the timestamp and body, computed with the secret of your endpoint. Recompute it on your side and compare before you trust the payload.

Can signers sign inside my app?

Yes. Request an embedded signing link for a recipient and load it in an iframe or a web view. The signer stays in your product, and the audit trail and sealed PDF are the same as for an emailed envelope.

For developers

eSignature API for Sending and Embedded Signing

The SignElectronically eSignature API creates envelopes from your templates, returns signing links you can embed in your own product, and posts signed webhooks when a document is viewed, signed or completed. API envelopes use the same plan quota.

See Pro plan Try the editor

REST over HTTPS, JSON in and out, included in Pro.

POST /api/v1/envelopes

curl https://signelectronically.com/api/v1/envelopes \
  -H "Authorization: Bearer se_live_8f2c..." \
  -H "Content-Type: application/json" \
  -d '{
    "template_id": 412,
    "subject": "Order form, Harbor Logistics",
    "recipients": [
      {"role": "Buyer", "name": "Jordan Avery",
       "email": "[email protected]"},
      {"role": "Finance", "name": "Priya Kaur",
       "email": "[email protected]"}
    ],
    "fields": {"order_total": "$11,600"}
  }'

What you can build

Three jobs the API takes over

Create and send

Start an envelope from a template or an uploaded PDF, set recipients and order, prefill text fields from your data.

Embed the signing step

Get a signing link that is safe to frame, so customers sign an order or an agreement without leaving your checkout or portal.

React to events

Receive a signed POST when an envelope is sent, viewed, signed, completed, declined, voided or expired, then fetch the sealed PDF.

Integration path

From API key to first signed document

1

Create an API key

In the developer settings of a Pro team. Give each system its own key so you can revoke one without touching the others.
2

Build a template

Set up roles and fields once in the editor. Your code then only passes people and values.
3

Create an envelope

POST the template id, recipients and field values. The response holds the envelope id and status.
4

Send or embed

Let us email the signers, or request an embedded link per recipient and show it inside your app.
5

Listen for completion

On the completed event, download the sealed PDF and the certificate and store them next to your record.

200 OK

{
  "id": "env_01JB7Q2M9K",
  "status": "sent",
  "recipients": [
    {"role": "Buyer", "status": "sent", "order": 1},
    {"role": "Finance", "status": "waiting", "order": 2}
  ],
  "quota": {"used": 39, "limit": 2000}
}

Templates keep the layout out of your code. If legal changes a clause, they update the eSignature template and your integration keeps working.

Webhooks

Signed events with automatic retries

Webhook deliveries

https://app.yourproduct.com/hooks/esign · signed with HMAC SHA-256

envelope.completed2026-10-09 09:16:02 UTC 200 delivered
envelope.signed2026-10-09 09:15:58 UTC 200 delivered
envelope.viewed2026-10-09 09:12:40 UTC 200 delivered
envelope.sent2026-10-08 14:00:13 UTC 503 retried
envelope.sent2026-10-08 14:00:43 UTC 200 delivered

Each delivery includes the header X-SignElectronically-Signature with a Unix timestamp and an HMAC SHA-256 of the timestamp and the raw body. Verify it with your endpoint secret and reject anything older than a few minutes.

If your endpoint does not answer with a 2xx status, the delivery is retried with growing pauses, from 30 seconds up to two hours. The delivery log shows every attempt with its status code.

Events for sent, viewed, signed, completed, declined, voided and expired
One secret per endpoint, stored encrypted
Webhooks work on Plus even without the API

IT administrator checking access settings on a laptop in a server closet

Pricing model

One quota for app and API

API access by plan
	Plus	Pro	Enterprise
Webhooks	Included	Included	Included
REST API and API keys	Not included	Included	Included
Embedded signing	Not included	Included	Included
Envelopes per month, app and API together	500	2,000	5,000 and up
Seats	10	25	50 and up
Price, billed yearly	$74/mo	$249/mo	from $499/mo

Several vendors sell their API as a separate product next to the per user plans. If that is what you are comparing, see the HelloSign alternative and DocuSign alternatives pages. Every API envelope gets the same audit trail as one sent by hand. Plans are on pricing, and the product overview is on the homepage.

Questions

eSignature API FAQ

An eSignature API lets your own software create documents for signature, send them, embed the signing step and fetch the signed result, without a person clicking through a web app. It turns signing into one step of your product or back office flow.

Add signing to your product

Pro includes the API, embedded signing, 25 seats and 2,000 envelopes a month.

See pricing