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Must APP be a reserved keyword in connection strings? #484
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Hi oscarrobertson, thank you for opening this issue!
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on Apr 9, 2026 Hi oscarrobertson - thanks for raising this, it's a valid question.
The APP keyword is reserved because mssql-python uses it to set the application identifier to
MSSQL-Pythonin every connection. This serves one fundamental purpose:
Telemetry & diagnostics: It allows our team to track driver adoption and usage patterns across SQL Server instances, which helps us prioritize investment and improvements for the Python driver.We understand this is a limitation for users who rely on APP to identify their own applications in sys.dm_exec_sessions, SQL Server Profiler traces, or similar monitoring tools. We appreciate the feedback and recognize this is a legitimate use case.
We'll track this as a feature request. Thanks again for the feedback!
Thanks Sumit Sarabhai (@sumitmsft) - telemetry across our estate is basically exactly what we'd want to use it for also! A quick fix/compromise might just tacking what you need on to the the app string after it's been set by the user or something.
Thanks for the clarification oscarrobertson I can understand your use case and that there would be other customers as well who may be using application name to get telemetry data for their estate.
The idea of allowing a user-specified suffix (application name) that gets appended to the driver name (MSSQL-Python), which would make application_name as "MSSQL-Python - YourAppName" sounds reasonable to us.
Please allow us sometime to triage this change. We will get back once we have confirmation on this. Hope that helps!
- Sumit
Reacted by Gord Thompson and oscarrobertsonimho, the jdbc mssql driver handles this the best. the driver version shows up in sys.dm_exec_sessions under "client_interface_name" as values like "Microsoft JDBC Driver 13.2".
Having the version number is very helpful in identifying drivers with CVE's, etc.
is it possible to override the generic "ODBC" with something like "ODBC 18.0 / mssql-python 1.6.0" ?
if not (due to ODBC driver limitations), then allowing the "YourAppName" suffix for "App=" as described above is acceptable.
Reacted by oscarrobertson
Hi, the library currently enforces APP as a reserved keyword in connection strings https://github.com/microsoft/mssql-python/wiki/Connection-to-SQL-Database#reserved-connection-string-keywords
Is there a good reason for this? I don't see any justification in the PR 8ed531e (although there is reference to docs/connection_string_allow_list_design.md which I cannot find)
We use currently use APP internally for passing application names and find it quite useful!