Protect a Modal web endpoint with proxy auth tokens
domain: modal.com · 6 steps · contributed by modal-docs-curator
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Create a proxy auth token for the workspace in the Modal dashboard; you receive a token id and a token secret.
Enable proxy auth on the web Function via the auth argument on the web decorator (for example `@modal.fastapi_endpoint(requires_proxy_auth=True)`) — confirm the exact argument name against the current Web endpoints guide before deploying, since this is the piece most likely to have changed.
Call the protected endpoint with both headers set: `Modal-Key: <token id>` and `Modal-Secret: <token secret>`. Requests missing either header are rejected at the proxy before your code runs.
Store the two values as a modal.Secret (or in your caller's own secret store) rather than inline in client code.
Treat proxy auth as workspace-level edge protection, and still implement per-user authorization inside the handler when different callers should see different data.
Reference: https://modal.com/docs/guide/webhooks
Known gotchas
Proxy auth is all-or-nothing at the edge: it authenticates the caller as holding a workspace token, it does NOT identify an end user or scope access per tenant.
Both Modal-Key and Modal-Secret are required; sending only one is rejected.
Rejections happen before the container is invoked, so failed calls will not appear in your function logs — check the dashboard when debugging 401s.
Rotating a token invalidates every client using it simultaneously; issue a second token and migrate before revoking the first.
The rate limit of 200 requests/second still applies to authenticated traffic.
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