PDFPipe

Nuxt / certificates

Certificate PDFs in Nuxt

Post your certificate HTML to a render API from a defineEventHandler in server/api, then return the response body from the event handler. No browser binary in your Nuxt deployment.

Why certificates become PDFs

A certificate is meant to be shown to a third party who has no relationship with the issuing system, and often printed. A link that could rot is not a credential. That is the difference between a document and a view of a database, and it is why training providers, course platforms and event organisers keep asking for this.

What a certificate has to carry

Before any of the code below matters, the template has to produce a document that is actually a certificate. These are the fields that make it one, and the ones a reader or an auditor will look for first.

  • the recipient full name exactly as they gave it
  • the achievement, named precisely enough to be checked
  • the issue date, and an expiry where the credential lapses
  • a unique certificate ID that a verifier can look up
  • the issuing body and an authorised signature or seal

Turning your Vue components, rendered with the server renderer template into a document

You already have the markup. Await renderToString(createSSRApp(Invoice, props)) gives you it as a string, which is the only input the render needs. Nitro compiles the same server code to a dozen deployment presets, several of which have no filesystem and no ability to spawn a process. Anything that assumes a local binary ties you to the node preset.

The Nuxt implementation

$fetch ships with the runtime, so this adds no dependency. The render happens in a defineEventHandler in server/api, and you return the response body from the event handler.

typescript
// server/api/certificates/[id]/pdf.get.ts
import { createSSRApp } from "vue";
import { renderToString } from "vue/server-renderer";
import CertificateDocument from "~/documents/CertificateDocument.vue";
import { documentStyles } from "~/documents/styles";

export default defineEventHandler(async (event) => {
  const id = getRouterParam(event, "id");
  const certificate = await getCertificate(id);

  const markup = await renderToString(createSSRApp(CertificateDocument, { certificate }));
  const html = `<!doctype html><html><head><meta charset="utf-8">
<style>${documentStyles}</style></head><body>${markup}</body></html>`;

  // arrayBuffer, explicitly. $fetch parses by content type and will try to make
  // sense of PDF bytes as text, which corrupts the file silently.
  const pdf = await $fetch<ArrayBuffer>("https://api.pdfpipe.xyz/v1/pdf", {
    method: "POST",
    headers: { Authorization: `Bearer ${useRuntimeConfig().pdfpipeKey}` },
    body: { html, options: { format: "A4", printBackground: true } },
    responseType: "arrayBuffer",
  });

  setHeader(event, "Content-Type", "application/pdf");
  setHeader(event, "Content-Disposition", `attachment; filename="certificate-${id}.pdf"`);
  return new Uint8Array(pdf);
});

The CSS that makes a certificate page correctly

The layout problem specific to this document is that the design is fixed and usually landscape, so it must fit exactly one page regardless of how long the recipient's name is. These rules handle it.

css
/* Exactly one landscape page, whatever the name's length. */
@page {
  size: A4 landscape;
  margin: 0;
}

.certificate {
  width: 297mm;
  height: 210mm;
  break-after: avoid;
  display: grid;
  place-items: center;
}

/* Long names shrink rather than wrap onto a second line. */
.recipient {
  font-size: clamp(28px, 5vw, 54px);
  text-wrap: balance;
}

What goes wrong in Nuxt

$fetch parses the response by content type and will try to make sense of PDF bytes as text. Pass responseType: "arrayBuffer" or use the raw handler, or the document arrives corrupted with no error.

What people try first

Most Nuxt projects reach for puppeteer in a server route, with the same preset problem: it works under the node preset and nowhere else. 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 certificate lives afterwards

Rendering is the short part. The recipient keeps it indefinitely and may present it years later to an employer who will want to verify it. That is the argument for the ID field: the PDF is the artefact, but the ID is what makes it checkable after your system has changed.

Getting the document right

  • Check the recipient's name, which must render correctly for every alphabet your learners actually use.
  • Generation is triggered by a course or assessment being completed, so size the timeout for that path rather than for a health check.
  • Volume arrives in bursts, so queue the render rather than doing it inside the request that triggered it.
  • 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 certificates from Nuxt?

No. The render happens over HTTP, so your Nuxt deployment stays the size it is now. That is the main reason to use an API rather than puppeteer in a server route, with the same preset problem: it works under the node preset and nowhere else.

How do I stop a long certificate using all the memory?

Return the response body from the event handler. $fetch parses the response by content type and will try to make sense of PDF bytes as text. Pass responseType: "arrayBuffer" or use the raw handler, or the document arrives corrupted with no error.

What has to be on a certificate?

At minimum: the recipient full name exactly as they gave it; the achievement, named precisely enough to be checked; the issue date, and an expiry where the credential lapses. The one to get right before anything else is the recipient's name, which must render correctly for every alphabet your learners actually use.

Do I need to store the generated certificates?

Depends on the document, and this one has a clear answer: the recipient keeps it indefinitely and may present it years later to an employer who will want to verify it. That is the argument for the ID field: the PDF is the artefact, but the ID is what makes it checkable after your system has changed.

Can I keep my existing certificate template?

Yes, if it produces HTML. Whatever renders your certificate 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 Nuxt documents, and the same certificate in other stacks.

Invoice PDFs in Nuxt

an invoice is a legal record of a demand for payment

Receipt PDFs in Nuxt

a receipt is proof a payment happened

Report PDFs in Nuxt

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.

Certificate PDFs in Node.js

Using fetch, in a route handler that returns the response body directly.

Certificate PDFs in Python

Using httpx, in an async endpoint that returns a streaming response.

Certificate 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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