Next.js / contracts
Contract PDFs in Next.js
Post your contract HTML to a render API from a Route Handler returning a Response, then return a Response with the upstream body and a PDF content type. No browser binary in your Next.js deployment.
Why contracts become PDFs
A contract has to be fixed at signature. Both parties need to be certain they are looking at identical words, which a rendered page cannot guarantee. That is the difference between a document and a view of a database, and it is why legal and sales operations keep asking for this.
What a contract has to carry
Before any of the code below matters, the template has to produce a document that is actually a contract. These are the fields that make it one, and the ones a reader or an auditor will look for first.
- the parties, by legal entity name and registered number
- the effective date and the term
- numbered clauses with stable numbering, since amendments reference them
- the commercial schedule, usually as an annexe rather than in the body
- signature blocks with name, title and date for each party
Turning your React, rendered to a string on the server template into a document
You already have the markup. RenderToStaticMarkup(<Invoice {...data} />) gives you it as a string, which is the only input the render needs. This is the framework where the incumbent approach fails hardest. A serverless function has a hard bundle size limit, and a Chromium build does not fit inside it. That is why the ecosystem grew a whole genre of stripped Chromium packages, and why an HTTP render is the path of least resistance here rather than an optimisation.
The Next.js implementation
fetch ships with the runtime, so this adds no dependency. The render happens in a Route Handler returning a Response, and you return a Response with the upstream body and a PDF content type.
// app/contracts/[id]/pdf/route.ts
import { renderToStaticMarkup } from "react-dom/server";
import { ContractDocument } from "@/documents/contract";
import { documentStyles } from "@/documents/styles";
export async function GET(
_request: Request,
{ params }: { params: Promise<{ id: string }> },
) {
const { id } = await params;
const contract = await getContract(id);
// The style tag is the load-bearing part. Your app's CSS lives in a bundle the
// renderer will never fetch, so the document needs its styles inline.
const html = `<!doctype html><html><head><meta charset="utf-8">
<style>${documentStyles}</style></head><body>${renderToStaticMarkup(
<ContractDocument contract={contract} />,
)}</body></html>`;
const upstream = await fetch("https://api.pdfpipe.xyz/v1/pdf", {
method: "POST",
headers: {
Authorization: `Bearer ${process.env.PDFPIPE_KEY}`,
"Content-Type": "application/json",
},
body: JSON.stringify({
html,
options: { format: "A4", printBackground: true },
}),
});
if (!upstream.ok) {
return new Response("render failed", { status: 502 });
}
return new Response(upstream.body, {
headers: {
"Content-Type": "application/pdf",
"Content-Disposition": `attachment; filename="contract-${id}.pdf"`,
},
});
}The CSS that makes a contract page correctly
The layout problem specific to this document is that numbered clauses with cross-references, where a page break in the wrong place separates a clause from the term it defines. These rules handle it.
/* A clause must not be separated from the term it defines, and a
signature block alone on a final page invites a dispute. */
.clause { break-inside: avoid; }
.signatures { break-inside: avoid; break-before: avoid; }
p { orphans: 3; widows: 3; }
@page { size: A4; margin: 25mm 20mm; }What goes wrong in Next.js
renderToStaticMarkup gives you markup with no stylesheet attached, because your CSS lives in a bundle the PDF renderer will never load. Inline the styles into a style tag in the string you send, or the document renders with browser defaults.
What people try first
Most Next.js projects reach for puppeteer-core paired with a size-reduced Chromium package, which works but ties your deployment to a binary that has to be rebuilt for every runtime version bump. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.
Where the contract lives afterwards
Rendering is the short part. A contract is retained for the term plus the limitation period, which typically means well over a decade. Immutability matters more here than anywhere else on this list: both parties must be able to prove the words have not moved.
Getting the document right
- Check the parties and the effective date, which is what every later dispute turns on.
- Generation is triggered by agreement being reached, often with a signature workflow following, so size the timeout for that path rather than for a health check.
- These are produced one at a time by a person who is waiting, so latency is felt directly.
- Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.
Frequently asked
Do I need Chromium installed to generate contracts from Next.js?
No. The render happens over HTTP, so your Next.js deployment stays the size it is now. That is the main reason to use an API rather than puppeteer-core paired with a size-reduced Chromium package, which works but ties your deployment to a binary that has to be rebuilt for every runtime version bump.
How do I stop a long contract using all the memory?
Return a Response with the upstream body and a PDF content type. renderToStaticMarkup gives you markup with no stylesheet attached, because your CSS lives in a bundle the PDF renderer will never load. Inline the styles into a style tag in the string you send, or the document renders with browser defaults.
What has to be on a contract?
At minimum: the parties, by legal entity name and registered number; the effective date and the term; numbered clauses with stable numbering, since amendments reference them. The one to get right before anything else is the parties and the effective date, which is what every later dispute turns on.
Do I need to store the generated contracts?
Depends on the document, and this one has a clear answer: a contract is retained for the term plus the limitation period, which typically means well over a decade. Immutability matters more here than anywhere else on this list: both parties must be able to prove the words have not moved.
Can I keep my existing contract template?
Yes, if it produces HTML. Whatever renders your contract view today can render the same markup for the PDF, which is why the CSS above is the only new thing you write.
Related
Other Next.js documents, and the same contract in other stacks.
Invoice PDFs in Next.js
an invoice is a legal record of a demand for payment
Receipt PDFs in Next.js
a receipt is proof a payment happened
Report PDFs in Next.js
a report is a snapshot of numbers at a moment in time. Its whole value is that it does not change when the underlying dashboard does.
Contract PDFs in Node.js
Using fetch, in a route handler that returns the response body directly.
Contract PDFs in Python
Using httpx, in an async endpoint that returns a streaming response.
Contract PDFs in PHP
Using cURL, in a controller action that echoes the body with a PDF Content-Type.
The same thing in plain Node.js
Without the framework, using fetch directly.
When the output is wrong
Blank pages, missing backgrounds, breaks in the wrong place, by symptom.
All stacks and documents
The full grid of what this covers.
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