API documentation

Send any PDF for signing with a single POST. The letssign.now API reference, errors, recipes, support.

The whole signing flow — anchors, signers, dispatch, signed PDF, audit trail, webhooks — sits behind one Bearer-API-key authed endpoint at https://api.wesign.now/v1/*. No templates required, no portal redirect for the recipient, no SDK to install. Three real-life calls ship 90% of integrations.

https://api.letssign.now/v1 is a permanent alias of the same API. The Base URL section says exactly what is — and what isn't — the contract.

Three steps to ship

Mint an API key

Go to Developers → API keys in your workspace and click Create API key. Copy the wsk_live_… token — we only display the plaintext once. Keys minted before the September 2026 rename start with lsk_live_ and keep working unchanged.

Send your first signing request

Replace YOUR_KEY and run this in a terminal:

curl -X POST https://api.wesign.now/v1/signing-requests \
  -H "Authorization: Bearer YOUR_KEY" \
  -F "file=@contract.pdf" \
  -F 'signers=[{"email":"signer@example.com","role":"signer"}]'

Drop [[ls:signature:signer]] anywhere in your PDF and we place a signature field there. No marker? We auto-append a signature page. Need the signer to confirm an SMS code before they can sign? Add phone_e164 and require_sms_verification to the signer — see Second factor by SMS, and SMS verification for the whole flow.

(Optional) Receive real-time events

Register an outbound webhook at Developers → Webhooks (or pass callback_url per-request). We POST signing_request.signed as each signer completes, and document.completed with a key-authenticated signed-PDF URL when everyone's done. Every delivery is HMAC-signed (X-WeSign-Signature) — verify it before trusting the body.

Sending contracts you author once in the app? The Template quickstart goes from a template to a sealed PDF: a one-signer rich-text letter, or a PDF two people sign in order.

What's in this site

Quickstart

Your own PDF to a sealed, signed PDF in five minutes, terminal only.

Template quickstart

Author a template in the app, fill it over the API, follow two signers in order, download the result.

API overview

Base URL and its alias, versioning, the map of v1 resources.

OpenAPI spec

The machine-readable contract — import it into Postman, Insomnia or a client generator.

Authentication

Bearer keys, key format, rotation, error shape.

Create a signing request

The big endpoint. Multipart or JSON, signers, placement, SMS second factor. Read one signer, remind, withdraw.

Placement modes

Anchors, auto-append, or explicit coordinates — and why manual placement is retired.

Documents

GET a document and its signers, signed-PDF download, audit-trail PDF.

Templates

Instantiate a locked template with field_values; stage for review first.

Prepare a fill in your app

Read a template's contract, ask your user for what it needs, dry-run, then send.

Webhooks

Events we emit, signature verification in Node and PHP, retry semantics.

Idempotency

Safely retry network blips without double-sending.

Rate limits

60 requests/minute per API key. Retry-After on 429.

Errors

Stable error codes mapped to HTTP statuses.

Security

Encryption at rest and in transit, signature evidence, webhook signing.

How verification works

Hash lookup, PAdES validation, eIDAS QES detection, trust scope.

For AI assistants

Building the integration with an AI assistant or coding agent? Give it these instead of pasted pages. The two text files are generated from this site's source on every deploy, so they always match the pages.

llms.txt

Every page with a one-line summary, the base URL, keys and versioning, and the machine-readable sources.

llms-full.txt

Every page of this site as plain Markdown, in one file.

Integrator FAQ

Short answers to what integrating apps ask most: observers, AES by SMS, languages, parallel signing, dates.

OpenAPI spec and changelog

The contract at /openapi.json; every change with a stable id at /api-changelog.json.