How to Fix: json.decoder.JSONDecodeError: Expecting value

You tried to parse some JSON data (usually from an API or a file), but Python choked. The error message JSONDecodeError Expecting value can be confusing if you’re not sure what it means.

The error Expecting value: line 1 column 1 (char 0) is code for: “I looked for JSON data, but the file/response was empty or garbage.”

# Fix 1 — API: check status_code before calling .json()
response = requests.get("https://api.example.com/data")
if response.status_code == 200:
    data = response.json()
else:
    print(f"Error: {response.status_code} — {response.text}")

# Fix 2 — File: catch JSONDecodeError and fall back to a safe default
import json
try:
    with open("config.json", "r") as f:
        data = json.load(f)
except json.decoder.JSONDecodeError:
    data = {}  # Empty or corrupt file — use defaults

Cause 1: The API Error (Most Common)

You made a request, but the server returned an error (like a 404 or 500) instead of the JSON data you expected.

Problem Code:

import requests
# This URL might be broken or require a login
response = requests.get("https://api.example.com/private-data")

# CRASH! The server sent back "403 Forbidden" text, not JSON.
data = response.json()

The Fix: Always check the status_code before trying to parse the JSON.

response = requests.get("https://api.example.com/private-data")

if response.status_code == 200:
    data = response.json() # Safe!
    print(data)
else:
    print(f"Error: Server returned {response.status_code}")
    print(response.text) # Print the error message instead

Cause 2: Reading an Empty File

You tried to json.load() a file that is blank.

Problem Code:

with open("empty_config.json", "r") as f:
    data = json.load(f) # CRASH!

The Fix: Check if the file is empty, or use a try/except block.

import json

try:
    with open("config.json", "r") as f:
        data = json.load(f)
except json.decoder.JSONDecodeError:
    print("File is empty or invalid. Using default settings.")
    data = {} # Default

What This Error Exposes About Python’s JSON Parser Contract

JSONDecodeError: Expecting value: line 1 column 1 (char 0) is Python’s json module reporting that the very first character of its input does not match any valid JSON token. A valid JSON document must open with {, [, ", a digit, t (true), f (false), or n (null). An empty string, an HTTP error page, a 403 Forbidden message, or a plain text response all fail that check at character zero — hence char 0 in the error message.

The API scenario is the most dangerous because it fails silently up to the parse step. requests.get() succeeds, response exists, and the code looks correct — the crash only arrives at .json(). The status code check closes that gap: a 200 response guarantees the server intended to send data, while any 4xx or 5xx response signals that response.text holds an error message worth logging, not a JSON payload worth parsing.

The file scenario follows the same pattern with a different trigger: an empty file, a truncated write, or a race condition during a previous save operation. The try/except json.decoder.JSONDecodeError block is the correct defensive pattern — it handles empty files, malformed JSON, and partial writes in a single clause and keeps your program running with a safe default. For production pipelines reading config files or cached API responses, combine both patterns: validate the source before parsing and catch the decoder error as a final safety net.