Ansible from_json & to_json Filters: Parse & Generate JSON Data (Guide)
By Luca Berton · Published 2024-01-01 · Category: troubleshooting
How to parse and generate JSON in Ansible with from_json, to_json, to_nice_json filters. Convert strings to dicts, format output, API responses. Practical YAML playbook examples.
What Are from_json and to_json Filters?
The from_json and to_json filters convert data between JSON strings and Ansible data structures: • from_json: Parses a JSON string into a dictionary or list • to_json: Converts a variable (dict, list) into a JSON string • to_nice_json: Converts to human-readable formatted JSON
from_json: Parse JSON Strings
Use from_json when you receive JSON as a string (from API calls, command output, file reads):
Parse JSON from Command Output
Parse JSON from File
to_json: Convert to JSON Strings
Use to_json to convert Ansible variables to JSON format:
Write JSON to File
Send JSON in API Requests
to_nice_json: Human-Readable Output
to_nice_json produces formatted, indented JSON:
Output:
Control Indentation
to_nice_yaml: Convert to YAML Format
Convert variables to readable YAML:
Common Patterns
Chain Filters
Handle JSON in Loops
Merge and Convert
Error Handling
Invalid JSON
Default Values
FAQ
What is the difference between from_json and from_yaml?
from_json parses JSON strings only. from_yaml parses YAML strings (which is a superset of JSON). In practice, from_yaml can also parse JSON, but from_json is stricter and preferred when you know the input is JSON.
When do I need from_json vs just accessing the variable?
You need from_json when the data is a string containing JSON, not a parsed data structure. This happens with command output (register), file reads (slurp), and API responses returned as strings. If the variable is already a dict/list, you don't need it.
How do I handle nested JSON with special characters?
Use bracket notation for keys with dots or spaces: {{ (json_str | from_json)['my.key']['with spaces'] }}. For complex nested queries, use the json_query filter with JMESPath syntax.
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Category: troubleshooting