SvelteKit / certificates
Certificate PDFs in SvelteKit
Post your certificate HTML to a render API from a +server.ts endpoint returning a Response, then return a Response built from the upstream body. No browser binary in your SvelteKit 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 Svelte components, rendered server side template into a document
You already have the markup. Const { html, head } = Invoice.render(data) gives you it as a string, which is the only input the render needs. Which adapter you build with decides whether a browser binary can exist at all. adapter-node can host one; adapter-vercel, adapter-cloudflare and adapter-netlify cannot. Choosing an HTTP render keeps the adapter choice open.
The SvelteKit implementation
fetch ships with the runtime, so this adds no dependency. The render happens in a +server.ts endpoint returning a Response, and you return a Response built from the upstream body.
// src/routes/certificates/[id]/pdf/+server.ts
import { error } from "@sveltejs/kit";
import { PDFPIPE_KEY } from "$env/static/private";
import CertificateDocument from "$lib/documents/CertificateDocument.svelte";
import { render } from "svelte/server";
export async function GET({ params, fetch }) {
const certificate = await getCertificate(params.id);
// head carries the scoped styles. Without it the document renders with
// browser defaults, because the CSS file it would link is not reachable.
const { head, body } = render(CertificateDocument, { props: { certificate } });
const html = `<!doctype html><html><head>${head}</head><body>${body}</body></html>`;
const upstream = await fetch("https://api.pdfpipe.xyz/v1/pdf", {
method: "POST",
headers: {
Authorization: `Bearer ${PDFPIPE_KEY}`,
"Content-Type": "application/json",
},
body: JSON.stringify({
html,
options: { format: "A4", printBackground: true },
}),
});
if (!upstream.ok) error(502, "render failed");
return new Response(upstream.body, {
headers: {
"Content-Type": "application/pdf",
"Content-Disposition": `attachment; filename="certificate-${params.id}.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.
/* 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 SvelteKit
A component's render() output does not include its scoped styles unless you also emit the head string, and even then the styles reference a CSS file the renderer cannot fetch. Inline them into the markup you send.
What people try first
Most SvelteKit projects reach for puppeteer in a +server.ts route, which works locally with adapter-node and then fails on the first deploy to any edge target. 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 SvelteKit?
No. The render happens over HTTP, so your SvelteKit deployment stays the size it is now. That is the main reason to use an API rather than puppeteer in a +server.ts route, which works locally with adapter-node and then fails on the first deploy to any edge target.
How do I stop a long certificate using all the memory?
Return a Response built from the upstream body. A component's render() output does not include its scoped styles unless you also emit the head string, and even then the styles reference a CSS file the renderer cannot fetch. Inline them into the markup you send.
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 SvelteKit documents, and the same certificate in other stacks.
Invoice PDFs in SvelteKit
an invoice is a legal record of a demand for payment
Receipt PDFs in SvelteKit
a receipt is proof a payment happened
Report PDFs in SvelteKit
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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