How Do I Fix YAML Configuration Errors in Home Assistant?
- Indentation/spacing wrong (tabs vs spaces)
- Missing colon or wrong YAML syntax
- Invalid option for an integration
Problem Description
Home Assistant won't start or reload because of YAML configuration errors — a bad indent, a typo, or an invalid option stops it. HA validates configuration.yaml and its includes, and the Check Configuration tool plus the logs point to the exact line.
Why This Happens in Real Homes
YAML is whitespace-sensitive, so most Home Assistant config errors are indentation (spaces, never tabs), a missing colon, or an option that's invalid for an integration — and HA tells you the exact file and line. Always validate before restarting so a typo doesn't drop you into safe mode.
Start with Developer Tools > YAML > Check Configuration, which reports the specific problem, and fix the flagged line. Watch for duplicate keys, wrong quoting, and !include paths, and remember HA updates occasionally deprecate config formats — an error right after an update often means a setting needs updating to the current syntax.
Symptoms
- HA won't start after a config edit
- Config check fails
- Error on a specific line
- Reload/restart rejected
- Integration config invalid
- Indentation error
- Duplicate key error
- Safe mode after a bad config
Recognize these? Here's what usually causes it.
Common Causes
- Indentation/spacing wrong (tabs vs spaces)
- Missing colon or wrong YAML syntax
- Invalid option for an integration
- Duplicate keys
- Wrong data type/quoting
- !include path wrong
- Secret not defined in secrets.yaml
- Deprecated config after an update
Most fixes happen in the first 3 steps.
Always backup configuration.yaml before major edits.
Tools & Requirements
These tools will help you complete this fix.
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Step-by-Step Solution
Use the configuration checker before restarting
Go to Developer Tools > YAML > Check Configuration. This validates your configuration.yaml and all included YAML files for syntax errors without restarting Home Assistant. If it reports 'Configuration valid,' you can safely restart. If it reports errors, it shows the file, line number, and error description. Always check configuration before restarting — a syntax error in configuration.yaml prevents Home Assistant from starting, which can lock you out if you do not have SSH or file access.
Fix common YAML syntax errors
The most common YAML mistakes: missing colons after keys ('platform mqtt' instead of 'platform: mqtt'), incorrect indentation (YAML uses spaces, never tabs — use 2 spaces per indent level), missing quotes around strings containing special characters (colons, brackets, percent signs), and duplicate keys in the same block (YAML silently uses the last one). A YAML linter in your editor (VS Code with the YAML extension, or the Home Assistant config editor) catches most of these before you save.
Check included files and packages
If your configuration.yaml uses '!include' or '!include_dir_merge_named' to split configuration across files: the error may be in an included file, not configuration.yaml itself. The configuration checker reports the specific file and line. Known problem: moving a section to a separate file but forgetting to update the indentation (included files should start at the root level, not indented under the include statement). Check each included file independently.
Fix template and Jinja2 errors
Jinja2 template errors in automations, scripts, or template sensors are a frequent source of config failures. Common mistakes: using '{{ states.sensor.name }}' (returns the full object) instead of '{{ states("sensor.name") }}' (returns the state value), missing closing braces, or referencing an entity that does not exist yet. Test templates in Developer Tools > Template before adding them to configuration files — the template editor shows live output and errors.
Recover from a broken configuration
If Home Assistant fails to start after a bad config change: access the configuration files directly via SSH, Samba share, or the File Editor add-on (if it was installed before the failure). Revert the last change in configuration.yaml. If you cannot identify the bad change, rename configuration.yaml to configuration.yaml.broken and create a minimal configuration.yaml with just 'homeassistant:' and 'default_config:' — this starts HA in a minimal state. Then incrementally re-add sections from the broken file, checking configuration between each addition.
Quick Solutions
Still having issues? This is usually the deeper cause below.
If this comes back after following these steps, check whether a recent app or firmware update reset a default setting — the fix works, but the setting gets reverted silently.
Place your hub in a central location in your home, elevated off the floor and away from your WiFi router by at least 3 feet. This provides the best Zigbee and Z-Wave signal coverage to all corners of your house.
Home Assistant issues that only appear after restart are a well-known quirk — triggers that require prior state history simply can't fire until that history rebuilds.
- Indentation/spacing wrong (tabs vs spaces)
- Missing colon or wrong YAML syntax
- Invalid option for an integration
- Duplicate keys
- Wrong data type/quoting
Before you go — try one of these (they fix most cases).
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Official Manufacturer Manual
Home Assistant provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Home Assistant.
Source: home-assistant.io
Need More Help? Home Assistant Support
Note: The contact information below connects you directly to Home Assistant's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.
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