Before publishing, GTFS feeds should be validated in order to catch errors. A number of different validation tools exist. Some tools check individual feeds while others are made to be integrated into software.
For GTFS-Static
MobilityData gtfs-validator Verifies feed conformity to the official GTFS specification. At present, the software supports the validation of file structure and is ready for semantic validation. This tool is under active development.
FeedValidator - Verifies that the feed conforms to the requirements defined in the GTFS-static reference.
ScheduleViewer - Visualizes geospatial and stop time feed data. This is not representative of how feed data will look in other applications; it is a basic tool for testing. Examine routes and schedules to ensure that the data feed correctly represents the system.
The Chouette project - Managed by the French Agency for Multimodal Information and Ticketing. Contains validation functionality and can translate between various formats.
GTFS-realtime
GTFS-realtime Validator - A tool created by the Center for Urban Transportation at the University of South Florida to verify that your real-time feed data correctly matches your GTFS dataset and contains all required information.
For software developers:
gtfs-realtime-validator-lib - Integrates GTFS-realtime validation rules into software. See the transit-feed-quality-calculator for an example of using the gtfs-realtime-validator-lib library in another project.