Save the PDF to a file in Python with requests

For documents big enough that you would rather not hold them twice in memory, stream the download with stream=True and iter_content, extend a bytearray, and write once at the end. The receipt's bytes field is the truth the write is checked against; a short download raises instead of passing.

The recipe

import requests
from pathlib import Path

ORIGIN = "https://webcapture.io"

receipt = requests.post(
    f"{ORIGIN}/v1/convert",
    headers={"Authorization": "Bearer wc_your_key", "Content-Type": "application/json"},
    json={"url": "https://example.com/"},
    timeout=60,
).json()

# the download url names /v1/conversions/<id>.pdf at the serving origin
chunks = bytearray()
with requests.get(
    receipt["download"],
    headers={"Authorization": "Bearer wc_your_key"},
    stream=True,
    timeout=60,
) as res:
    res.raise_for_status()
    for chunk in res.iter_content(chunk_size=65536):
        chunks.extend(chunk)

if len(chunks) != receipt["bytes"]:
    raise RuntimeError(f"short download: {len(chunks)} of {receipt['bytes']} bytes")
Path("whitepaper.pdf").write_bytes(chunks)

The size check is the point of the recipe: the endpoint tells you exactly how many bytes the render produced, so a proxy that truncates the transfer or a disk that fills mid-write becomes a loud error instead of a corrupt pdf.

Same-key GET: 401 without it; 404 for another key.

The fields this recipe uses

• url: the page address to render, a public http(s) URL.

Related

• Next: Get a free key to run this Python recipe, or read the API docs.
• More recipes: Python: convert from a URL, curl: name the file, Node: download with the key.
• The webcapture API reference: every field the convert endpoint admits, with the response shapes and the error table.
• The recipes hub: the same endpoint in the other languages.
• Going deeper: the automations hub carries the same streaming GET inside n8n, Zapier, and Make workflows.
• The free URL to PDF tool: try the render in a browser before you wire the call.

Method

Source: convert field reference, checked 2026-10-05. Corrections.