How to Add E-Signatures to Your v0 App

If your team builds with v0, adding legally binding e-signatures is a natural extension of your existing workflow. Firma.dev integrates through standard Next.js route handlers, which means v0's AI can generate most of the integration code from a prompt. Your app deploys to Vercel as usual, and the signing infrastructure runs on Firma.dev's API.

This guide covers what the integration enables and how to think about it from a product perspective. For the full technical walkthrough with code samples and deployment steps, head to the v0 integration guide on our docs.

Why v0 + Firma.dev

v0 is one of the fastest ways to build production-ready Next.js applications. You describe what you want, v0 generates the code, and it deploys straight to Vercel. It's become a go-to tool for teams that want to ship quickly without sacrificing code quality.

Firma.dev fits that speed. The integration uses standard API calls from your app's backend, so there's no SDK to install, no complex authentication setup, and no additional infrastructure to manage. Your developer stores a Firma.dev API key as an environment variable, adds a route handler, and the signing feature works in both preview and production environments.

At €0.029 per envelope (~3 cents USD), e-signatures don't become a meaningful line item as you scale. No monthly minimums, no contracts, no per-seat pricing. You pay for the envelopes your app sends and nothing else.

What the integration covers

Once connected, your v0 app gets access to the full Firma.dev signing workflow:

Sending documents for signature. A user action in your app triggers a signing request through the Firma.dev API. The recipient recieves the document by email, signs it, and the completed document is stored automatically. You can use this for contracts, onboarding forms, consent documents, or any workflow that needs a legally binding signature.

Embedded signing. If you'd rather keep signers inside your app, Firma.dev provides an embeddable e-signature experience that loads in an iframe. The signer completes the document without leaving your product, which keeps the experience seamless and reduces drop-off.

Webhook notifications. When a document is signed, declined, or expires, Firma.dev sends an event to your app's webhook endpoint. Your backend can react automatically, whether that means updating a database, triggering the next step in a workflow, or sending a confirmation to the user.

Multi-tenant architecture. Building a SaaS product where each customer needs their own signing flow? Firma.dev's customer workspaces for multi-tenant e-signatures give each customer isolated templates, branding, and usage tracking without you having to build tenant separation yourself.

How the integration works

The setup follows a pattern that's standard in the Next.js ecosystem, and v0's AI assistant can handle most of it from a prompt. At a high level:

1. Your developer adds the Firma.dev API key to v0's Vars panel, which syncs it securely to Vercel

2. A route handler calls the Firma.dev API from the server side, keeping the API key out of client code

3. Your frontend form or button triggers that route handler when a user needs to send a document

4. An optional webhook route handler listens for completion events

The full integration guide walks through each step with code examples, including how to connect the Firma.dev MCP server so v0's chat generates accurate API calls while building.

Deployment

v0 projects deploy to Vercel automatically. Environment variables set in v0's Vars panel carry over to production, so the Firma.dev integration works in preview deployments and live without any additional configuration. If your team needs different API keys per environment (staging vs. production, for example), those can be scoped in the Vercel dashboard.

E-signature security and compliance

Documents signed through Firma.dev are legally binding under the ESIGN Act and UETA in the United States, and support SES and Advanced Electronic Signatures (AdES) under eIDAS in Europe. All signing data is hosted on AWS infrastructure in the EU (Paris region) with CloudFront distribution from Stockholm.

Your API key stays server-side. It's stored as an encrypted environment variable in Vercel and is never exposed in client-side code. For more on how Firma.dev handles e-signature security, encryption, and audit trails, see our security page.

Getting started

No sales calls, no procurement process. Your team can start right now:

1. Create a free Firma.dev account at app.firma.dev

2. Set up a template with the signing fields your documents need

3. Follow the v0 integration guide to connect the API

Firma.dev includes 25 free envelopes to test with, so your team can validate the full flow in a v0 preview deployment before any cost kicks in.

Get started with Firma.dev for free, no credit card required.