If you're seeing this error when trying to connect an account:
400 - Error origin not allowed for redirect_uri for platform:jsWhat's going on?
During the authentication flow, your app exchanges a code for an access token by calling POST /v3/connect/token. This error means the platform type on your redirect URI is set to JavaScript, which tells Nylas to expect the request from a browser.
If your app actually makes this call from your backend server (which most apps do), the security check fails — and you get this error.
How to fix it
- Head over to your Nylas Dashboard
- Go to App Settings → Redirect URIs
- Find the redirect URI mentioned in the error
- Change the platform from JavaScript to Web
- Hit Save
That should do it! Your authentication flow will start working right away.
How do I know which platform to pick?
| Platform | Choose this if... |
|---|---|
| Web | Your server handles the token exchange — this is the most common setup |
| JavaScript | Your app runs entirely in the browser with no backend server |
If your app does run entirely in the browser and JavaScript is the right choice, make sure the Origin field in your redirect URI settings matches your app's domain exactly — for example, https://myapp.example.com (no trailing slash, no path).
Still stuck?
We're happy to help! Reach out to Nylas Support with your application ID and redirect URI, and we'll get you sorted.
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