Custom REST API Endpoints Returning Errors in Base44
You've created custom API endpoints in your Base44 app to expose data or functionality to external systems, mobile apps, or other services, but the endpoints return errors when called. The errors may be 404 (not found), 500 (server error), or authentication failures.
Custom API endpoints enable Base44 apps to communicate with other systems and are essential for building more complex integrations. When they fail, any external system depending on your Base44 app's API stops working.
The issue may be specific to certain HTTP methods (GET works but POST doesn't), certain endpoints, or certain callers (works from Postman but not from the external system).
Error Messages You Might See
Common Causes
- The API endpoint URL path is different between the editor and the published app
- Authentication requirements are not being met by the calling system
- The endpoint expects a specific request body format that the caller isn't providing
- CORS headers are not set, blocking calls from browser-based clients
- The endpoint logic contains an error that causes a 500 error for certain input data
How to Fix It
Test the endpoint directly using Postman or curl with the exact URL, headers, and body that the external system should be sending. This isolates whether the issue is with the endpoint configuration or the caller.
Check authentication requirements: if the endpoint requires an API key or token, ensure the caller is including it in the correct header format.
For APIs that need to support multiple callers, handle various payload formats, or require complex business logic, a developer can build robust endpoints with proper validation, error handling, and documentation.
Real developers can help you.
Jaime Orts-Caroff
I'm a Senior Android developer, open to work in various fields
Milan Surelia
Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems.
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Jared Hasson
Full time lead founding dev at a cyber security saas startup, with 10 yoe and a bachelor's in CS. Building & debugging software products is what I've spent my time on for forever
Basel Issmail
’m a Senior Full-Stack Developer and Tech Lead with experience designing and building scalable web platforms. I work across the full development lifecycle, from translating business requirements into technical architecture to delivering reliable production systems.
My work focuses on modern web technologies, including TypeScript, Angular, Node.js, and cloud-based architectures. I enjoy solving complex technical problems and helping teams turn product ideas and prototypes into working platforms that can grow and scale.
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Luca Liberati
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Simon A.
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Bastien Labelle
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Get HelpFrequently Asked Questions
Why does my Base44 API endpoint return 404?
The endpoint URL may differ between editor and published environments. Verify the exact URL by checking your published app's API settings and test with a tool like Postman.
How do I authenticate calls to my Base44 API endpoints?
Check your API endpoint's authentication settings. You may need to include an API key in the request header. Test the exact headers with Postman to verify what's required.