# PytestUnknownMarkWarning: Unknown pytest.mark.slow - is this a typo?  You can register custom marks to avoid this warning

- **ID:** `python/pytest-mark-unknown-warning`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

A custom marker (e.g., @pytest.mark.slow) is used but not registered, so pytest emits a warning and -m 'slow' filtering may not behave as expected.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 7.x | active | — | — |
| 8.x | active | — | — |

## Workarounds

1. **** (98% success)
   ```
   # pytest.ini
[pytest]
markers =
    slow: marks tests as slow
    integration: requires external services
   ```
2. **** (95% success)
   ```
   # pyproject.toml
[tool.pytest.ini_options]
markers = [
  "slow: marks tests as slow",
  "integration: requires external services",
]
   ```

## Dead Ends

- **** — Silences the warning but -m filtering still doesn't recognize the mark. (80% fail)
- **** — -k matches names, not markers; results differ. (70% fail)
- **** — Works but duplicates config; pytest.ini is simpler and canonical. (30% fail)