I built an HTML to PDF API for real-world web apps (SPAs, iframes, dashboards)

GoPDFGenie — Sun, 16 Nov 2025 14:17:58 +0000

Most of us hit this at some point:

“I need to generate a PDF from HTML… and it has to look exactly like the page.”

So you pick a CLI tool or library, wire it up, and it kind of works…

until you have:

heavy JavaScript
charts and dashboards in iframes
React / SPA pages that render mostly on the client
and a production server that now runs some fragile, homegrown setup

I’ve been through this a few times, so I ended up building a service I wish I had earlier:

a hosted HTML to PDF/PNG API called GoPDFGenie.

This post is about:

why I built it,
how the async API works (jobs),
a simple curl/pseudocode example,
and how you can run it hosted or self-hosted.

The pain with “just use a PDF library”

Tools like wkhtmltopdf and many HTML to PDF wrappers are fine when:

the HTML is simple,
there’s almost no JS,
and you don’t care too much about pixel-perfect layout.

In real products I kept seeing:

PDFs that didn’t match the live UI
things breaking when the frontend team changed layout or added JS
weird layout quirks in some HTML engines
and the ongoing cost of maintaining your own conversion infrastructure

Once SPAs, dashboards, and iframes show up, the “just install X and call it a day” story falls apart.

What I wanted instead

For my own projects, I wanted a service that:

Has a conversion engine tuned for modern web apps
Handles SPAs, iframes, dashboards, charts
Is hosted, so I don’t maintain conversion infra again
Has simple, usage-based pricing
Still allows self-hosting/on-prem if a team needs that

So I built GoPDFGenie.

👉 Live site: https://gopdfgenie.com

👉 API docs (Swagger UI): https://gopdfgenie.com/swagger-ui/index.html

👉 GitHub examples: https://github.com/gopdfgenie/html-to-pdf-api

Real-world pages I tested it on

When I started building this, I didn’t just test on tidy demo pages.

I tried it on real, messy, modern sites like:

public charting pages on TradingView (https://www.tradingview.com)
long, responsive templates like Story and Solid State from HTML5 UP (https://html5up.net/story, https://html5up.net/solid-state)
interactive chart galleries like Datawrapper’s scatter plot examples (https://academy.datawrapper.de/article/414-examples-of-datawrapper-scatter-plots-time)

In my own testing, a lot of the online HTML to PDF tools I tried — including several that show up right at the top when you search for “html to pdf” — would:

fail to finish the conversion,
return an error or blank page, or
produce PDFs where key parts of the page (charts, iframes, long sections) were missing or cut off.

That experience is a big part of why I built GoPDFGenie and tuned it specifically for JS-heavy, layout-rich pages, so you can feed it “real” URLs instead of only perfectly controlled internal templates.

What GoPDFGenie does (and how the async API works)

At a high level, GoPDFGenie is:

“Give me a URL or HTML, I’ll run it through a modern HTML-to-document pipeline, and you fetch the PDF/PNG when it’s ready.”

The API is asynchronous:

You create a conversion job.
The API returns a jobId.
You poll the job status.
When it’s COMPLETED, you fetch the result file as PDF or PNG.

Base URL:

https://gopdfgenie.com/api/v1

Main endpoints:

POST /convert/url/async — create a job from a public URL
POST /convert/async — create a job by uploading HTML/ZIP via multipart/form-data
GET /jobs/{jobId}/status — check job status
GET /jobs/{jobId}/result — download the finished PDF/PNG

Every request uses bearer auth:

Authorization: Bearer YOUR_API_KEY

Hosted SaaS and self-hosted option

By default GoPDFGenie is a hosted HTML to PDF API SaaS:

Sign up on the site
Get an API key
Call https://gopdfgenie.com/api/v1/...
Pay via a credit-based model (Free, Starter, Pro, Business; credits are based on output size)

For teams that must keep everything in their own environment (compliance, data residency, locked-down networks), I also offer a self-hosted / on-prem license:

Same core conversion engine
You run it inside your own infra (containers/VMs, etc.)
Direct contract for licensing & support

If that’s interesting, there’s an Enterprise section + contact form on the pricing page.

Pseudocode: full async flow

apiKey   = "YOUR_API_KEY"
apiBase  = "https://gopdfgenie.com/api/v1"

# 1) Submit a URL conversion job
response = HTTP_POST(
    url    = apiBase + "/convert/url/async?orientation=portrait&outputFormat=pdf&pageSize=A4&quality=STANDARD",
    headers = {
        "Authorization": "Bearer " + apiKey,
        "Content-Type": "application/json"
    },
    body = { "url": "https://example.com/report" }
)

jobId = response.jobId

# 2) Poll status until job is done
loop:
    wait a few seconds
    statusResponse = HTTP_GET(
        url = apiBase + "/jobs/" + jobId + "/status",
        headers = { "Authorization": "Bearer " + apiKey }
    )

    status = statusResponse.status

    if status == "FAILED":
        stop with error

    if status == "COMPLETED":
        break loop

# 3) Download the resulting PDF/PNG
fileBytes = HTTP_GET(
    url = apiBase + "/jobs/" + jobId + "/result",
    headers = { "Authorization": "Bearer " + apiKey }
)

save fileBytes as "output.pdf"

You can translate this to Node, Python, Java, etc. I’ve put more concrete examples in the GitHub repo.

Where this is useful

Invoices / billing PDFs that must match your UI
Analytics dashboards and JS charts you need as PDF reports
React / SPA routes like /reports/123 that rely on client-side rendering

Forem: GoPDFGenie