# 404 Not Found: The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.

- **ID:** `python/flask-blueprint-url-prefix-double-slash`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Blueprint registered with url_prefix='/api/' and route '/items' produces '/api//items'; client requests '/api/items'.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 2.x | active | — | — |
| 3.x | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   app.register_blueprint(bp, url_prefix='/api')  # no trailing slash
   ```
2. **** (85% success)
   ```
   Print app.url_map to verify generated rules: print(app.url_map)
   ```

## Dead Ends

- **** — Does not fix the doubled slash. (75% fail)
- **** — Masks the real prefix bug and creates security surface. (70% fail)