Does YAML use tabs or spaces for indentation?

YAML uses spaces. Tabs are not allowed for indentation in the YAML spec. Most teams use 2 spaces per indentation level.

How do I fix a YAML indentation error?

Paste the YAML into a formatter. It will re-indent every line with a consistent number of spaces and report any structural problems.

How many spaces should I indent YAML?

2 spaces per level is the most common convention. 4 spaces also works as long as the whole file uses the same amount consistently.

YAML Indentation

Spaces, tabs, common errors, and how to fix indentation fast.

The one rule

YAML uses spaces to show nesting. Tabs are not allowed for indentation. Mixing spaces and tabs is the most common cause of a YAML parse error.

How many spaces?

The YAML spec does not mandate a number, but the convention is 2 spaces per indentation level. Four spaces also works as long as every level in the same file uses the same step.

# 2-space indentation (recommended)
config:
  debug: true
  services:
    - api
    - db

# 4-space indentation (valid, but be consistent)
config:
    debug: true
    services:
        - api
        - db

Common indentation errors

Tab characters copied from a terminal or editor configured for tabs.
Inconsistent depth — one list item indented 2 spaces, the next 3.
Indenting the dash differently from the list item content.

# Bad: mixing depths
items:
  - name: api
   port: 8080   # one space too many

# Bad: tab before "debug"
config:
	debug: true

How to fix YAML indentation

Open the YAML formatter.
Paste your messy YAML into the input box.
Copy the output, which is re-indented with consistent 2-space spacing.

For structural problems, run the same text through the YAML validator to see the exact line number of the error.

Why does indentation matter in YAML?

Unlike JSON, YAML has no braces or closing tags. The structure is entirely defined by indentation. If the indentation is wrong, the parser cannot tell what belongs to what.

Related guides

YAML format example — a readable annotated sample.
YAML validation guide — common errors and fixes.
What is YAML? — a plain-language introduction.