Ansible "Syntax Error while loading YAML" in CI

By Daniel Zoghalchali·Latchkey

The YAML parser could not load a playbook or vars file. Indentation, an unquoted value containing a colon, or a leading Jinja brace are the usual culprits.

What this error means

ansible-playbook (or --syntax-check) fails with "Syntax Error while loading YAML", pointing at a line and column. The play never runs because the document cannot be parsed.

ansible

ERROR! Syntax Error while loading YAML.
  mapping values are not allowed in this context

The error appears to be in '/runner/_work/repo/site.yml': line 8, column 22

    msg: Deploy complete: v1.2  <-- the unquoted colon breaks parsing

Common causes

Unquoted colon or special character

A value like "Deploy: v1" without quotes makes YAML read a mapping where a scalar was intended.

Indentation or a leading Jinja brace

Wrong indentation, or a value starting with {{ at the line start, must be quoted or YAML rejects it.

How to fix it

Quote ambiguous values and fix indentation

Wrap values with colons or leading braces in quotes, and keep consistent two-space indentation.

site.yml

- name: Notify
  debug:
    msg: "Deploy complete: v1.2"     # quotes protect the colon
- name: Templated
  debug:
    msg: "{{ release_version }}"      # quote leading Jinja braces

How to prevent it

Quote values containing colons or starting with Jinja braces.
Use consistent two-space indentation; avoid tabs.
Run --syntax-check (and yamllint) in CI before the play.

Frequently asked questions

What causes "Ansible "Syntax Error ... YAML""?