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Fix Home Assistant YAML errors by reading the exact log message, identifying whether the failure is YAML parsing, Home Assistant validation, automation setup, or template rendering, correcting the relevant file or value, and running a configuration check before reloading or restarting. The same workflow covers errors such as found character 't', could not find expected ':', Message malformed:, and Cannot specify both 'trigger' and 'triggers'.
Home Assistant’s current interfaces change slightly between releases and installation types, but the diagnostic sequence remains the same: inspect the loaded configuration directory, edit only the file named by the error, validate it, then apply the smallest possible reload.
How do I fix common Home Assistant YAML configuration errors?
Start with the complete error, not with a guess about what is wrong. Open Settings > System > Logs, copy the warning or error including its file path and line number, and determine which configuration directory the running installation uses. Home Assistant reports that directory during startup. If an integration offers diagnostics, download them before changing files so setup details are preserved.
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| Failure layer | Typical symptoms | What to inspect |
|---|---|---|
| YAML parsing | found character 't' that cannot start any token, could not find expected ':', or a generic YAML error |
Indentation, spaces, colons, quotes, tabs, and file encoding |
| Home Assistant schema validation | not a valid value for dictionary value @ data or an option-specific message |
Allowed keys, value types, nesting, and entity IDs |
| Automation setup | Message malformed:, an automation that saves but does not load, or a duplicate legacy/current key |
Trigger, condition, action structure and included automation files |
| Template rendering | An automation loads but fails when executed, or reports an undefined variable, iterable, or template syntax error | Jinja spelling, filters, punctuation, and runtime state values |
Make one logical change at a time. This prevents a new parser error from hiding the original schema or runtime problem.
Capture the exact error and locate the file Home Assistant reads
- Open the logs. Go to Settings > System > Logs and filter for the integration, automation, script, or template named in the message. Record the filename, line number, column, and the first useful “caused by” detail.
- Confirm the configuration directory. Do not assume the editor opened the directory used by the running instance. The startup log identifies Home Assistant’s active configuration directory; check that path before editing.
- Identify the configuration source. A failure can come from
configuration.yaml, an included file,automations.yaml, a package, or an integration-specific YAML file. Follow the path in the log rather than searching every file. - Preserve context. If the integration provides a diagnostics download, obtain it from its integration page before making changes. Diagnostics can show setup details that a short log line omits.
Keep the error text unchanged when searching the official Home Assistant documentation. Exact strings usually lead to a more relevant remedy than a broad search for “YAML error.”
Correct the YAML syntax errors first
Replace tabs with spaces
YAML indentation must use spaces. The parser message found character 't' that cannot start any token means a tab appears where YAML expects indentation. Configure your editor to insert spaces, then convert existing indentation tabs in the affected file. Do not replace tabs inside a quoted text value unless the value itself is meant to change.
automation:
- alias: Turn on hallway light
trigger:
- platform: state
entity_id: binary_sensor.hallwayThe example uses two spaces for each indentation level. The exact width is not important; consistent nesting is.
Repair indentation and the space after a colon
YAML structure is defined by indentation. A child key aligned with its parent becomes a different mapping, while a child shifted one space too far can become invalid or attach to the wrong item. A colon that introduces a value normally needs a following space. Check the line reported by the parser and the preceding line, because the actual mistake is often just above the location where parsing becomes impossible.
# Incorrect
alias:Turn on light
# Correct
alias: Turn on lightFor lists, keep the dash at the level of the list and indent the item’s keys beneath it:
action:
- service: light.turn_on
target:
entity_id: light.hallwayDo not duplicate top-level sections
configuration.yaml cannot contain multiple top-level sections with the same name. Adding a second sensor:, automation:, or other duplicate section can overwrite, invalidate, or ambiguously combine configuration depending on how it is parsed. Use the documented nesting or platform-list arrangement for multiple entries, or place separate content in included files with distinct include points.
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Save files as UTF-8
Home Assistant configuration files must be UTF-8 encoded. A log message about UTF-8 decoding means the editor saved bytes in another encoding or inserted invalid characters. Reopen the affected file in an editor that can choose encoding, convert it to UTF-8, save, and run the configuration check again. Do not “fix” an encoding error by deleting arbitrary non-ASCII characters if they are meaningful names or labels.
Fix values that YAML interprets differently than you intended
Quote state strings such as on and off
YAML can interpret words such as true, Yes, ON, and off as Boolean values. Home Assistant then receives a Boolean where an integration expects a state string and may report not a valid value for dictionary value @ data. Quote the value when it represents text:
to: 'on'
from: 'off'Use the type the option documents. A real Boolean option should remain unquoted; quoting it changes it into a string.
Match entity IDs exactly
Home Assistant is case-sensitive, and entity IDs use lowercase. binary_sensor.Front_Door does not match binary_sensor.front_door. If you are unsure of an ID, open Settings > Tools > States, find the entity, and copy its exact entity ID into YAML. Also verify that the entity still exists after a device or integration rename.
Check keys and nesting against the feature’s current schema
A syntactically valid document can still be rejected when a key is obsolete, misspelled, placed at the wrong level, or assigned the wrong type. Read the complete validation message and correct the named option instead of changing indentation randomly. Current and legacy forms must not be mixed in the same object.
Make Jinja templates valid YAML and valid templates
Quote a single-line template
YAML can treat an unquoted {{ or {% as flow-style syntax. Quote a one-line Jinja expression so YAML sees one scalar value:
value_template: "{{ states('sensor.temp') | float > 20 }}"Use single or double YAML quotes consistently. If the expression contains the same quote character, choose the other YAML quote style or escape the character.
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Use a block scalar for multiline templates
For a template spanning several lines, use a block scalar such as > and indent every template line beneath it:
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The temperature is {{ states('sensor.temp') | float }} degrees.
The window is {{ states('binary_sensor.window') }}.The indentation belongs to YAML; the template text itself must remain consistently indented. A block scalar avoids forcing line breaks and quote escaping into a long expression.
Separate parse errors from render errors
If Home Assistant refuses to load the file, fix YAML quoting and indentation first. If the file loads but an automation fails when it runs, use the template troubleshooting details:
- An undefined variable may be misspelled, unavailable in that context, or genuinely unset. Check the variable name and provide a suitable default where the feature supports one.
mapandselectfilters produce iterables. Add| listbefore counting or indexing when the next operation requires a list.- A template syntax error usually points to a typo, missing punctuation, unmatched quote, or invalid operator on the reported line.
Test the expression in Home Assistant’s template editor when available, using real entity IDs and states from the current installation.
Run a configuration check before restarting
Always validate after editing. A configuration check reads the files and reports errors before a restart can interrupt automations or leave the instance running with a partially changed setup.
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Use the Settings interface
For automation YAML workflows, open Settings > Tools > YAML > Check configuration. The check reports whether the configuration is valid and lists errors or warnings. UI labels can differ slightly by Home Assistant release and installation type, so use the YAML or configuration-check entry under Settings if the exact wording has changed.
Use the command line
Home Assistant documents this command:
hass --script check_configRun it in the environment that contains the Home Assistant installation. The script supports options for common troubleshooting needs:
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| Option | Purpose |
|---|---|
-c |
Specify a configuration directory when the active directory is not the default. |
-f |
Show the configuration files used by the check, useful for confirming includes. |
--json |
Return machine-readable JSON output for scripts or log collection. |
--fail-on-warnings |
Return a nonzero status when warnings should fail an automated check. |
Installation-specific command paths differ between Home Assistant OS, Container, and other deployments. Run the command inside the Home Assistant installation environment and specify -c when necessary.
Use the homeassistant.check_config action
The homeassistant.check_config action lets an automation or script request a check. It reads and validates configuration files without loading them, creates a persistent notification, and writes details to the logs when it finds errors. Administrator rights are required. This action is useful when you need a repeatable check from the Home Assistant interface rather than shell access.
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Resolve automation-specific errors
Read every word after “Message malformed:”
When saving an automation produces Message malformed:, the detail normally identifies the invalid trigger, condition, action, or option. Correct that named field and save again. Do not treat the prefix as the diagnosis; the text following it is the part that tells you which schema rule failed.
A YAML error shown in the automation editor instead points to syntax, commonly indentation or a missing space after a colon. Fix parsing first, then address any schema message that appears after the file becomes valid YAML.
Remove legacy keys when a current key is present
Home Assistant’s automation schema has changed names over time. An object must not contain both an old key and its current replacement. Examples include:
| Do not mix | Use one current structure | What to do with old content |
|---|---|---|
trigger: and triggers: |
Use the form documented for your current release. | Move the trigger entries under that key and remove the other key. |
platform: and trigger: |
Use the current trigger structure. | Do not paste a legacy example beside a current trigger definition. |
service: and action: |
Use the current action structure. | Move service calls into the current action form and delete the duplicate legacy key. |
Copying examples from different Home Assistant release eras can create duplicate keys. Compare the complete automation with the syntax documented for the version running your instance.
Restore the include for UI-created automations
If automations created in the UI disappear or stop loading from automations.yaml, check that configuration.yaml still contains:
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Choose reload or restart deliberately
Prefer a reload for a configuration type that supports it. Reloading applies supported YAML changes without stopping the whole Home Assistant process. The exact reload command is under the relevant integration or automation controls.
Restart when the changed component has no reload operation, when a supported reload did not apply the new values, or when the documentation for that integration requires a restart. A restart interrupts running automations and scripts, so avoid doing it during a critical sequence and warn other users of the interruption.
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|---|---|---|
| Logs and integration diagnostics | Warnings, setup failures, and integration-specific context | Read-only investigation; diagnostics can be downloaded when offered. |
| Settings > Tools > YAML configuration check | Validate from the UI before applying changes | Reports errors and warnings without a restart. |
hass --script check_config |
Command-line validation, explicit directories, and structured output | Checks configuration without restarting Home Assistant. |
homeassistant.check_config |
Run a check from an automation or script | Reads files, creates a persistent notification, and logs details; administrator rights are required. |
| Reload | Apply supported configuration changes | Usually avoids stopping Home Assistant. |
| Restart | Apply changes when reload is unavailable or ineffective | Stops and starts Home Assistant and interrupts automations and scripts. |
Worked diagnoses for common messages
“found character ‘t’ that cannot start any token”
- Open the file and line named in the log.
- Display whitespace in the editor and replace indentation tabs with spaces.
- Check nearby list dashes and nested keys for alignment.
- Run the configuration check before reloading.
“could not find expected ‘:’”
- Inspect the reported line and the line immediately above it.
- Look for a missing colon after a key, an unclosed quote, or a multiline value that was not given a block scalar.
- Confirm that a colon inside plain text is quoted when YAML could interpret it as structure.
- Validate again; the parser may report a later line even though the typo is earlier.
“not a valid value for dictionary value @ data”
Check the option’s expected type and the value’s YAML interpretation. Quote state text such as 'on' or 'off' when a string is required, verify spelling and capitalization, and confirm that the key belongs at that nesting level.
“Cannot specify both ‘trigger’ and ‘triggers’”
Remove one of the two keys and place all trigger entries under the current key required by your release. Apply the same rule to other legacy/current pairs such as platform/trigger and service/action. Then run a configuration check before saving or reloading the automation.
Prevent the next configuration failure
- Use an editor configured for spaces and UTF-8.
- Make small, reviewable edits instead of replacing an entire configuration file with a copied example.
- Keep indentation visibly consistent and quote values whose type could be ambiguous.
- Copy entity IDs from Settings > Tools > States rather than typing them from memory.
- Check templates separately from the YAML structure, especially after changing an entity or attribute name.
- Run the configuration check after every edit that affects an include, automation, integration, or package.
- Reload only the affected configuration when supported, and reserve restarts for changes that require them.
- Keep a known-good backup so a failed experiment can be reverted without reconstructing the file.
Home Assistant’s YAML syntax documentation notes that most things can be configured directly in the user interface and that you never need to touch a YAML file for those tasks. YAML remains useful for integrations and power-user features, but avoiding unnecessary manual edits removes an entire class of parser and schema mistakes.
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