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

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

## Root Cause

A custom marker such as @pytest.mark.slow is used without being registered in pytest.ini, pyproject.toml, or conftest.py, so pytest treats it as a typo.

## 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: needs external services
   ```
2. **** (98% success)
   ```
   # pyproject.toml
[tool.pytest.ini_options]
markers = [
  'slow: marks tests as slow',
]
   ```

## Dead Ends

- **** — Silences the warning but --strict-markers will still fail the run, and the marker remains unregistered. (70% fail)
- **** — Changes test semantics; skip is not the same as a user-defined tag used for selection. (80% fail)