{"id":"9f7f33fb9d084c8a","repo":"tiangolo/fastapi","slug":"incorrect-username-or-password-9f7f33","errorCode":null,"errorMessage":"Incorrect username or password","messagePattern":"Incorrect username or password","errorType":"http","errorClass":"HTTPException","httpStatus":401,"severity":"error","filePath":"docs_src/security/tutorial004_py310.py","lineNumber":124,"sourceCode":"    user = get_user(fake_users_db, username=token_data.username)\n    if user is None:\n        raise credentials_exception\n    return user\n\n\nasync def get_current_active_user(current_user: User = Depends(get_current_user)):\n    if current_user.disabled:\n        raise HTTPException(status_code=400, detail=\"Inactive user\")\n    return current_user\n\n\n@app.post(\"/token\")\nasync def login_for_access_token(\n    form_data: OAuth2PasswordRequestForm = Depends(),\n) -> Token:\n    user = authenticate_user(fake_users_db, form_data.username, form_data.password)\n    if not user:\n        raise HTTPException(\n            status_code=status.HTTP_401_UNAUTHORIZED,\n            detail=\"Incorrect username or password\",\n            headers={\"WWW-Authenticate\": \"Bearer\"},\n        )\n    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)\n    access_token = create_access_token(\n        data={\"sub\": user.username}, expires_delta=access_token_expires\n    )\n    return Token(access_token=access_token, token_type=\"bearer\")\n\n\n@app.get(\"/users/me/\")\nasync def read_users_me(current_user: User = Depends(get_current_active_user)) -> User:\n    return current_user\n\n\n@app.get(\"/users/me/items/\")\nasync def read_own_items(current_user: User = Depends(get_current_active_user)):","sourceCodeStart":106,"sourceCodeEnd":142,"githubUrl":"https://github.com/tiangolo/fastapi/blob/42a41db11f6882807ac3c057b942178d53b97438/docs_src/security/tutorial004_py310.py#L106-L142","documentation":"Default-parameter twin of error 51: `/token` raises HTTP 401 'Incorrect username or password' (with `WWW-Authenticate: Bearer`) when `authenticate_user` returns falsy. A `DUMMY_HASH` verify runs for unknown users to flatten timing differences. Behavior matches the Annotated version.","triggerScenarios":"`POST /token` with an unknown username or a known username + wrong password; both hit `if not user:` at line 123.","commonSituations":"Password typo; user not provisioned; argon2id hash mismatch from a different hasher; pwdlib missing/wrong version; JSON body instead of form data.","solutions":["POST credentials form-encoded.","Produce the stored hash with the same `PasswordHash.recommended()` the app uses.","Install `pwdlib[argon2]` if using argon2id.","Verify the username exists and the hash verifies."],"exampleFix":"# before\n# hash made by a different hasher => 401\n# after\nfrom pwdlib import PasswordHash\nph = PasswordHash.recommended()\ndb['johndoe']['hashed_password'] = ph.hash('secret')","handlingStrategy":"try-catch","validationCode":"def is_form_login(username: str, password: str) -> bool:\n    return bool(username) and bool(password)\n# POST as application/x-www-form-urlencoded when True","typeGuard":"def is_credentials_error(resp) -> bool:\n    return getattr(resp, 'status_code', None) == 401 and \\\n           resp.json().get('detail') == 'Incorrect username or password'","tryCatchPattern":"try:\n    tok = client.post('/token', data={'username': u, 'password': p})\n    tok.raise_for_status()\nexcept httpx.HTTPStatusError as e:\n    if e.response.status_code == 401 and 'Incorrect' in e.response.text:\n        show_user_friendly_login_error()\n    raise","preventionTips":["Hash stored passwords with the server's PasswordHash.recommended().","Install pwdlib's argon2 extra when using argon2id.","POST form-encoded; keep the generic message; rate-limit."],"tags":["authentication","oauth2","login","jwt","security","fastapi"],"analyzedSha":"42a41db11f6882807ac3c057b942178d53b97438","analyzedAt":"2026-08-04T19:23:32.007Z","schemaVersion":2}