Resend API Key Tester
Enter your Resend API key below and click 'Test Key' to check if it works. This tool will send a request to Resend asking, "Does this key work?" and return a response with an explanation.
🔑 How to Get Your API Key
2. Go to API Keys section in your dashboard
3. Click 'Create API Key'
4. Provide a name and copy the generated key
5. Free tier: 3,000 emails/month
Test Your API Key
🔧 Alternative: cURL Command
You can also test your API key using cURL from your terminal:
curl -sS -X POST https://api.resend.com/emails -H 'Authorization: Bearer {{KEY}}' -H 'Content-Type: application/json' -d '{"from":"test@example.com","to":["test@example.com"],"subject":"Test Email","text":"Hello world!"}'
💻 How to run this command in your terminal:
- Copy the command above by clicking the "Copy" button
- Open your terminal (Command Prompt on Windows, Terminal on Mac/Linux)
- Paste the command using Ctrl+V (Windows/Linux) or Cmd+V (Mac)
- Press Enter to execute the command
- Check the response - you'll see either a success message or an error explaining what's wrong
💡 Terminal Tips:
- Make sure you have
curlinstalled (it comes pre-installed on Mac and most Linux systems) - On Windows, you may need to install curl or use PowerShell's
Invoke-WebRequestinstead - If you see "command not found", try
curl --versionto check if it's installed
🔧 Common Resend API key errors
❌ 401
Cause: Invalid or revoked API key.
Fix: Create a new key at resend.com/api-keys and paste it here.
❌ 403
Cause: The sending domain isn't verified for this key.
Fix: Verify a sending domain at resend.com/domains, or use onboarding@resend.dev for tests.
🔑 API Key Format Guide
Your Resend API key should follow the correct format:
✅ Valid Format
re_abc123...
Starts with "re_". Resend keys start with re_.
❌ Invalid Format
invalid_key_format
Missing required prefix, wrong length, or incorrect format
How to check if your Resend API key is working
- Copy your key from resend.com/api-keys.
- Paste it above and click Test Key.
- Green means valid; red shows the error and fix.
❓ Frequently Asked Questions
How do I test my Resend API key?
Simply paste your API key into the form above and click "Test Key". Our tool will make a test request to Resend to verify your key works.
Is it safe to test my API key here?
Yes! All testing happens in your browser - we never see or store your API keys. The key never leaves your device.
What if my API key test fails?
Check the error message above. Common issues include invalid keys, expired keys, insufficient credits, or rate limiting. Use the troubleshooting guide above for specific solutions.
Can I test multiple API keys?
Yes, you can test as many keys as you need. Each test is independent and secure.
Why do I need to use the terminal?
Some providers use server-side authentication for enhanced security. The terminal method provides direct access to test your API key with full compatibility.
Use Cases
- Quickly verify if your Resend API key is valid
- Troubleshoot API key-related issues with detailed error messages
- Understand Resend API response codes and their meanings
- Validate email service credentials before sending campaigns
- Check email delivery permissions and quotas
Supported Resend Responses
This tool handles all Resend error codes, including:
- 200 (OK): Key is valid and working correctly
- 201 (Created): Request successful and resource created
- 202 (Accepted): Request accepted and being processed
- 400 (Bad Request): Invalid request format or parameters
- 401 (Unauthorized): The API key is incorrect or invalid
- 403 (Forbidden): API key lacks required permissions
- 404 (Not Found): Requested resource doesn't exist
- 429 (Rate Limit Exceeded): Too many requests in a short period
- 500 (Server Error): Resend servers are experiencing issues
Refer to the Resend Documentation for more details.