json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

Python · updated 2026-11-02

Raised by json.loads, and by requests Response.json() (as requests.exceptions.JSONDecodeError, a subclass), when the very first character is not valid JSON. "line 1 column 1 (char 0)" means nothing parseable came back at all: an empty body, an HTML error page, a plain-text message or a redirect page.

Traceback (most recent call last):
  File "/srv/app/sync.py", line 22, in fetch_items
    items = resp.json()["items"]
            ^^^^^^^^^^^
requests.exceptions.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

Quick fix

Check the response before parsing it: log resp.status_code, the Content-Type header and the first 200 characters of resp.text. Call resp.raise_for_status() first so 4xx and 5xx error pages raise an HTTP error with the status instead of a JSON error, and treat 204 or an empty body as "no data".

1. Log status_code, headers["Content-Type"] and resp.text[:200] for the failing call.
2. Call resp.raise_for_status() before resp.json().
3. Handle 204 No Content and empty bodies explicitly.
4. If the body is HTML, look for a login page, a proxy or rate-limit page, or a wrong URL.
5. For files, check the file is not empty or still being written when it is read.

resp = session.get(url, timeout=10)
resp.raise_for_status()                      # 4xx/5xx raise HTTPError with the status
if resp.status_code == 204 or not resp.content:
    return []
if "json" not in resp.headers.get("Content-Type", ""):
    raise ValueError(f"expected JSON from {url}, got {resp.headers.get('Content-Type')}: {resp.text[:200]!r}")
items = resp.json()["items"]

Why it happens

Other fixes

• Wrap external API calls in one helper that checks status and content type before parsing.
• Record the status code and a short body excerpt with the error so the cause is visible in your error tracker.
• Read files that may carry a BOM with encoding="utf-8-sig".

Same error, other wording

• json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
• requests.exceptions.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
• json.decoder.JSONDecodeError: Extra data: line 1 column 5 (char 4)

Related errors

• requests.exceptions.ConnectionError: HTTPSConnectionPool(host='api.example.com'...
• KeyError: 'email'
• UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte

References: Python: json.JSONDecodeError, Requests: Response.json() and raise_for_status()