Skip to content
For developers

eSignature SDKs for .NET, Node.js, Python, Java, and PHP

Add eSignatures to your app or website with BoldSign’s official SDKs. Signers finish the document inside your own page, and you get back a digitally signed PDF.

Create free API sandboxBook a walkthrough
  • Signing embedded in your page
  • Webhooks for every status change
Your CompanyPreviewSend
Assignee
Emily Carter
SERVICE AGREEMENT
Company signatureSign here*
Client signatureSign here*
// POST /v1/template/createEmbeddedRequestUrl { "title": "Service Agreement", "message": "Please review and sign.", "roles": [{ "roleIndex": 1, "signerName": "Emily Carter", "signerEmail": "emily@cubeflakes.com", "signerOrder": 1 }] }
Sample of BoldSign embedded in a company website: a service agreement opened for sending inside yourapp.example, and the JSON request body that creates the embedded request from a template

Trusted by 100,000+ organizations worldwide

Samsonite
Ryanair
Hyatt
Sony
Crumbl Cookies
Payroc
Cost Plus
What you can build

What can you build with an eSignature SDK?

With BoldSign’s eSignature SDKs, your app sends documents, embeds signing in an iframe, and tracks each request.

Works in: your own application or website, through the BoldSign API.

Languages

eSignature SDKs for .NET, Node.js, Python, Java, and PHP

BoldSign maintains an official eSignature SDK in each of these five languages. Each installs from its usual package registry.

How it works

How do you send a document for signature from your code?

With a BoldSign SDK, you create a client with your API key. Then you describe the signer and the field, and call send.

  1. Authenticate

    Create the document client with your API key or an OAuth 2.0 token.

    import boldsignconfiguration = boldsign.Configuration(api_key="YOUR_API_KEY")with boldsign.ApiClient(configuration) as api_client: document_api = boldsign.DocumentApi(api_client)
    Python excerpt from the BoldSign SDK sample, highlighted lines shown first: configuration = boldsign.Configuration(api_key="YOUR_API_KEY") with boldsign.ApiClient(configuration) as api_client:

  2. Place the signature field

    Set the page, position, and size of each field the signer fills in.

    signature_field = boldsign.FormField( fieldType="Signature", pageNumber=1, bounds=boldsign.Rectangle(x=50, y=50, width=200, height=25), isRequired=True,
    Python excerpt from the BoldSign SDK sample, highlighted lines shown first: fieldType="Signature", pageNumber=1, bounds=boldsign.Rectangle(x=50, y=50, width=200, height=25),

  3. Name the signer and send

    Add the signer’s name and email, attach the file, and call send. The call returns a document ID.

    signer = boldsign.DocumentSigner( name="Signer Name", emailAddress="s•••@example.com", formFields=[signature_field],document_created = document_api.send_document(send_for_sign=send_for_sign)print(document_created.document_id)
    Python excerpt from the BoldSign SDK sample, highlighted lines shown first: name="Signer Name", emailAddress="s•••@example.com", document_created = document_api.send_document(send_for_sign=send_for_sign) print(document_created.document_id)
After you send

How do you know when a document is signed?

BoldSign posts each status change to your webhook URL. Your app hears when a signer views, signs, or declines a document.

  • Check status any time

    Read a document’s status with its document ID.

  • Download the signed PDF

    Download the completed PDF and the audit trail once everyone has signed.

  • Remind or revoke

    Send a reminder, or revoke a request, from your code.

Why BoldSign

Why choose BoldSign for your development team

BoldSign suits teams that want signing inside their product without building the signing part themselves.

  • Build it all before you go live

    Every API call works in a free sandbox, so you finish the integration before you pay.

  • A check for each signer

    Ask any signer for an access code, an email or SMS code, KBA, or an ID check.

  • A coding assistant in your editor

    The BoldSign Assistant MCP server answers SDK questions and writes sample code in VS Code, Cursor, or Claude.

  • SDKs from the team behind the API

    BoldSign’s own developers maintain all five SDKs alongside the API.

Customer stories

How product teams build signing into their apps

Payroc and Alliance Regulatory use the BoldSign API, so their customers sign without leaving their platforms.

Limits

Limits and costs to know before you build with BoldSign

BoldSign prices its API by the envelope and caps requests per account. Prices are in USD.

  • $30a month on the Enterprise API planIncludes 40 envelopes and 2 users. Then $0.75 per envelope and $28 per user.
  • 2,000API requests an hour, liveCalls over the limit return HTTP 429.
  • 50API requests an hour in the sandboxCounted per account, not per key.
  • 14 dayshow long sandbox documents lastEach one carries a watermark until it is deleted.

Add-on prices, charged per use

  • Bulk send and bulk links cost $0.25 per envelope.
  • SMS delivery and SMS codes cost $0.20 per SMS. WhatsApp delivery costs $0.10 per message.
  • ID verification costs $2 per completed attempt. KBA costs $1.50 per attempt.
  • A qualified electronic signature costs $3 per signing attempt.
See API pricing
Related

More guides for building with the eSignature API

Common questions

Questions about eSignature SDKs

Is BoldSign a digital signature SDK?

Yes. BoldSign’s SDKs collect electronic signatures from people. Each completed PDF is digitally signed with an AATL certificate. Popular PDF viewers show if the file changed after signing.

Which eSignature APIs provide SDKs for faster implementation?

BoldSign provides five official SDKs, so your first signature request is a short script. Other languages call the REST API directly. Test it in a free API sandbox.

How should developers compare eSignature APIs for SDKs, webhooks, and authentication?

Look for an official SDK in your language, webhooks, OAuth 2.0, and a free sandbox. BoldSign offers all four. See how its webhooks work.

How do developers authenticate with the BoldSign API?

Use an API key for server-to-server calls. Use OAuth 2.0 when users connect their own BoldSign accounts.

What changes when I move from the sandbox to production?

Swap your sandbox credentials for live ones and point webhooks at your live URL. Set the base URL for your region: US, Europe, Canada, or Australia.

What does the BoldSign API cost per envelope?

The Enterprise API plan starts at $30 a month with 40 envelopes. Each extra envelope costs $0.75, so 100 envelopes a month comes to $75. See API pricing.

Get started

Send your first document from code today

Create a BoldSign sandbox, install your language’s SDK, and send a test request.

Create free API sandboxBook a walkthrough
  • 30-day free trial
  • No credit card required

Last updated: October 17, 2026