🚨 Ansible Error: 'We were unable to read either as JSON nor YAML' — Cause, Fix, and Troubleshooting Guide

Overview

When you pass variables on the command line with -e/--extra-vars, Ansible tries to interpret the string. If it starts with { or [ it is parsed as JSON/YAML; otherwise it is treated as key=value pairs. If the value looks like structured data but is malformed, Ansible cannot decide and fails:

ERROR! We were unable to read either as JSON nor YAML, these are the errors we got from each:
JSON: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

Syntax Error while loading YAML.
  did not find expected node content

The extra-vars string is neither valid JSON nor valid YAML, and it is not a clean key=value list either.

Symptoms

• The playbook never starts; the error is about --extra-vars, not a host.
• It appears after adding a -e argument with braces, quotes, or spaces.
• Removing the -e argument makes the run start normally.

ansible-playbook site.yml -e {"env": "prod"}

ERROR! We were unable to read either as JSON nor YAML

Common Root Causes

1. Unquoted JSON eaten by the shell

-e {"env":"prod"} is mangled by the shell before Ansible sees it (braces and quotes are stripped/split).

2. Spaces in a key=value string

-e "name=my app" — the space splits it into a malformed second token.

3. Mixing JSON and key=value

-e '{"env":"prod"} region=us' cannot be both forms at once.

4. A bad @file reference

-e @vars.json where the file has trailing commas, single quotes, or invalid YAML.

How to diagnose

Print exactly what the shell passes to Ansible:

echo '{"env": "prod"}'      # verify quoting survives

If using a file, validate it independently:

python3 -c 'import json,sys; json.load(open("vars.json"))' && echo "valid JSON"

Fixes

Quote JSON as a single-quoted string

ansible-playbook site.yml -e '{"env": "prod", "region": "us-east-1"}'

Use the simple key=value form for scalars

ansible-playbook site.yml -e "env=prod region=us-east-1"

Pass complex data via a vars file

# extra.yml
env: prod
region: us-east-1
features:
  - metrics
  - tracing

ansible-playbook site.yml -e @extra.yml

Escape or avoid spaces in values

ansible-playbook site.yml -e '{"app_name": "my app"}'   # JSON handles the space

What to watch out for

• Always wrap inline JSON in single quotes so the shell does not strip braces and double quotes.
• key=value extra-vars are always strings; use JSON/YAML when you need lists, dicts, booleans, or numbers with correct types.
• Extra-vars have the highest precedence — a malformed one can also silently override a value you did not intend if it parses but is wrong.

Related

• Ansible Error: ‘Syntax Error while loading YAML’
• Ansible Error: ‘dict object has no attribute’
• Debugging Ansible Variable Precedence With AI