Learning Objective

By the end of this guide, you'll know how to generate a lemlist API key, copy and securely store it, and manage multiple API keys (rename, check usage, delete).

Why This Matters

API keys let you connect lemlist to external tools like Clay, Zapier, custom apps, or internal systems. Without an API key:

You can't integrate lemlist with third-party platforms
Automation workflows won't work
You're limited to manual data entry

Generating an API key unlocks:

✅ Automated workflows (add leads, trigger campaigns, sync data)
✅ Custom integrations with your tech stack
✅ Programmatic access to lemlist features

Prerequisites

Before generating an API key:

You have a lemlist account with access to Settings
You know which tool/app needs the API key (Clay, Zapier, custom integration)
You have a secure place to store the key (password manager recommended)

Step 1: Open Integrations (API Settings)

Click your profile icon (bottom-left corner), then select Settings
In Settings, go to Integrations, then click Generate

Step 2: Name and Create Your API Key

Give your API key a descriptive name to identify its purpose.

Examples:

Clay Integration
Zapier Automation
Custom CRM Sync

Enter the name, then click Create Key

Step 3: Copy and Securely Store Your API Key

⚠️ Critical: You can only view the API key once after generation. If you lose it, you'll need to generate a new one.

Copy the API key and paste it into:

A password manager (1Password, LastPass, Bitwarden)
A secure document
The integration tool that needs it (Clay, Zapier, etc.)

💡 Never share your API key publicly (don't paste it in Slack, email, or GitHub).

Step 4: Manage Your API Keys

Once generated, you can manage your API keys in the API keys section within Integrations. If the list is collapsed, click the arrow to expand it

Check last used time

The Last used column shows when each API key was last accessed

Use this to identify unused or inactive keys.

Rename an API key

Click the edit icon (✏️) next to the API key
Enter a new name
Save

Delete an API key

If an API key is no longer needed:

Click the delete icon (🗑️) next to the key
Confirm deletion

⚠️ Deleting an API key immediately revokes access for any integration using it. Make sure the key isn't actively in use before deleting.

How You'll Know It Worked

✓ API key appears in the API keys section with the name you assigned

✓ You successfully copied the API key and stored it securely

✓ The integration tool (Clay, Zapier, etc.) connects using the API key

✓ Last Used time updates when the key is actively used

To test, paste the API key into the integration tool and verify connection succeeds.

Troubleshooting

Issue: Can't find the API section

Root cause: You may not have the correct permissions, or the API section is hidden.

Fix:

Ensure you're logged in as an admin or have API access permissions
Contact your workspace admin if you don't see the API section

Issue: API key not working in integration

Root cause: API key copied incorrectly, expired, or revoked.

Fix:

Verify you copied the entire key (no extra spaces or characters)
Check if the API key was deleted or regenerated
Generate a new API key and update the integration

Issue: Lost API key before copying it

Root cause: API keys can only be viewed once during generation.

Fix:

Delete the lost API key
Generate a new API key
Copy and store it immediately in a password manager

Issue: API key shows "Never Used" but integration is working

Root cause: Last Used time may take a few minutes to update.

Fix:

Wait 5–10 minutes and refresh the page
If it still shows "Never Used" after 24 hours, verify the integration is using the correct key

Optimization Tips

Use descriptive names: Name API keys after their purpose (e.g., "Clay Integration," "Zapier Workflow") to easily identify them later.

Store in a password manager: Use 1Password, LastPass, or Bitwarden to securely store API keys with notes about where they're used.

Generate separate keys for each integration: Don't reuse the same API key across multiple tools. This makes it easier to revoke access without breaking other integrations.

Audit keys quarterly: Review your API keys every 3 months. Delete unused or inactive keys to reduce security risk.

Rotate keys periodically: For security, regenerate API keys every 6–12 months, especially for critical integrations.

Document key usage: Keep a note of which API key is used where (e.g., "Clay Integration key used in Clay table XYZ").

Monitor Last Used time: Check Last Used regularly to identify keys that may have been compromised or are no longer needed.