How to Fix the Invalid API Key Error from OpenAI in n8n

Go to platform.openai.com and sign in. Navigate to API Keys in the left sidebar. Check if the key you are using in n8n is listed. If the key shows as revoked, deleted, or is not present at all, it has been invalidated and must be replaced. Note that OpenAI only shows the last 4 characters of each key, so compare those with the key stored in n8n. Also check the Project column — if the key belongs to a specific project, it may not have access to all models.

If your key is invalid, create a new one. In the OpenAI dashboard, click 'Create new secret key'. Choose a descriptive name like 'n8n-production'. Select the project scope — use 'Default project' unless you have specific project isolation needs. Set permissions to 'All' for full model access. Copy the key immediately — OpenAI will not show it again. Store it securely in a password manager before pasting it into n8n.

In n8n, go to the main menu and click Credentials. Find the OpenAI API credential your workflow uses (it will be named something like 'OpenAI account'). Click on it to edit. Replace the API Key field with your new key. Make sure there are no leading or trailing spaces — this is a common cause of 'invalid key' errors. Click Save. Do not create a new credential unless you want to update multiple workflows separately; updating the existing credential automatically applies to all workflows that reference it.

1// To verify the key works, create a simple test workflow:
2// Trigger: Manual Trigger
3// Node: OpenAI → Message a Model
4// Model: gpt-4o-mini
5// Prompt: "Say hello"
6// Run the workflow — if it returns a response, the key is valid.

Even with a valid key, API calls will fail with a 401 or 429 error if your account has no billing method, has exceeded its spending limit, or has run out of free trial credits. Go to platform.openai.com → Settings → Billing. Verify that a payment method is on file, that your current balance is positive, and that your monthly usage limit is set high enough. For free trial accounts, check if your $5 credit has been used up — once it is gone, you need to add a payment method.

For production workflows, you should rotate API keys periodically for security. The safest approach: create a new key in OpenAI before revoking the old one. Update the n8n credential with the new key. Test the workflow. Only then revoke the old key in OpenAI. This ensures zero downtime. If you use environment variables for credentials in self-hosted n8n, update the environment variable and restart n8n. Never hardcode API keys in Code nodes or expressions — always use the credential system.

1// WRONG: Never put API keys in Code nodes
2// const apiKey = 'sk-abc123...'; // DO NOT DO THIS
3
4// RIGHT: Use n8n's credential system
5// In the HTTP Request node, use Predefined Credential Type → OpenAI API
6// Or reference via: {{ $credentials.openAiApi.apiKey }} in expressions
7// (only works in HTTP Request node header configuration)