Keep the provider credential private, and authorize the requests your own application accepts.
Keep credentials out of URLs
A market data key connects requests to an account and its allowance. Treat it as a credential, even when the API only reads data. Someone who obtains it may still consume capacity that your application depends on.
OWASP recommends HTTPS for REST services and warns against placing API keys in URLs, where they can appear in logs. Send credentials using the provider’s documented authentication header. HTTPS protects the connection; it does not make a credential safe to publish in your frontend. [1]
Give the browser a narrower interface
Our recommended web-app pattern is browser → your backend → data provider. The backend adds the provider key and returns only the data the interface needs. Do not embed the key in browser JavaScript, public environment variables, or a downloadable configuration file.
The backend route needs its own access controls. An unrestricted proxy can let other people spend your allowance without ever learning the key. Validate the requested symbol and interval, limit request volume, and reject arbitrary upstream URLs. Keep account-specific responses separated when sharing cached data. [1]
Plan for rotation before a leak
OWASP’s secrets-management guidance covers a credential’s full lifecycle, including storage, rotation, revocation, and expiration. Use your hosting platform’s secret facility, restrict access, and avoid copying production credentials into development environments.
Write down how your team replaces a key. If the provider supports overlapping keys, install and verify the replacement before revoking the old one. If only one active key is permitted, plan the transition around that restriction. For a known compromise, prioritize revocation over keeping the old credential working. [2]
Make troubleshooting safe
For request diagnostics, we suggest recording the endpoint, response status, duration, and a request identifier. Redact authentication headers and avoid dumping complete request objects into logs. A useful error report rarely needs the credential itself.
Review the places a key could escape: browser requests, build output, screenshots, support messages, and error reports. If exposure occurs, remove the published copy and revoke the credential; deleting a message or file does not invalidate a key that has already been copied. Test that the replacement works and that the revoked key is rejected. [2]
References
Primary sources for the technical details in this article. Implementation suggestions are our own.