Guides · Python · httpx

Capture a JavaScript-heavy page after it settles in Python with httpx

Render a client-side app too early and the capture shows the loading state, not the page: skeleton placeholders where cards should be, a spinner where the chart goes, grey boxes where lazy images land. The page "loaded" — the load event fired — but the app was still fetching its data. "wait_until": "networkidle" moves the goalpost: the render proceeds only after the page stops making network requests for a quiet period.

Below is a complete, runnable Python program using httpx (pip install httpx). It reads your API key from the SNAPDOK_KEY environment variable — free keys take about thirty seconds and need no card.

import os
import httpx

resp = httpx.post(
    "https://snapdok.io/v1/render",
    headers={"Authorization": "Bearer " + os.environ["SNAPDOK_KEY"]},
    json={
        "url": "https://your-app.com/report/42",
        "format": "png",
        "full_page": True,
        "wait_until": "networkidle",
        "delay": 500,
    },
    timeout=90,
)
resp.raise_for_status()

with open("settled.png", "wb") as f:
    f.write(resp.content)

The four stages, in order of patience: commit (bytes started arriving), domcontentloaded (HTML parsed), load (the default — static assets done), and networkidle (the network went quiet, which for an SPA usually means data fetched and rendered). delay then adds a fixed pause on top — the 500 ms here covers entrance animations and fade-ins that happen after the last fetch.

The cost of patience is time: networkidle on a page with analytics beacons or long-polling can take a while to go quiet, and a page that never goes quiet will run into timeout (a 504, never metered). If your page exposes a reliable "ready" element, wait_for_selector is the sharper tool — it waits for exactly the thing you care about, no more. There is a guide for it below.

Same endpoint, one more trick: if the page you are rendering has a form on it, adding "pdf_forms": true to a PDF render brings it back with real, fillable AcroForm fields — a PDF people can type into, not a picture of one. How that works.

Notes for httpx

httpx looks like requests but differs where it bites: it ships a 5-second default timeout, which a render that drives a real browser will blow through on heavier pages — hence the explicit timeout=90. raise_for_status() exists and behaves the same. If you are on asyncio already, the same call works with httpx.AsyncClient and await client.post(...) — the request body and headers are identical.

Response headers worth reading

Header	Meaning
`X-Page-Height`	Measured document height for the full-page capture.
`X-Cache`	Identical requests within 24h replay for free.

Full parameter reference: the docs. Hard numbers on caps and timeouts: limits.

Capture a JavaScript-heavy page after it settles in Python with httpx

Notes for httpx

Response headers worth reading

Related guides

Same task, other stacks

More with Python + httpx