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API Keys

API keys authenticate your requests to the Lettr API.

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Creating API Keys

Create keys in the dashboard or via API: 
const apiKey = await lettr.apiKeys.create({
  name: 'Production Server',
  permissions: ['emails:send', 'emails:read']
});

console.log(apiKey.key); // le_xxxxxxxxxxxx
// Store this key securely - it won't be shown again!

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Key Format

Lettr API keys follow this format: 
le_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  • le_ prefix identifies it as a Lettr key
  • 36 character random string

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Using API Keys

curl https://api.lettr.dev/v1/emails \
  -H "Authorization: Bearer le_xxxxxxxxxxxx" \
  -H "Content-Type: application/json"

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In SDKs

import { Lettr } from 'lettr';

const lettr = new Lettr('le_xxxxxxxxxxxx');
// or
const lettr = new Lettr(process.env.LETTR_API_KEY);

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Key Types

TypeUse CaseDashboard
Full AccessServer-side applications✅
RestrictedLimited permissions✅
TestDevelopment/testing✅

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Test vs Production Keys

FeatureTest KeyProduction Key
Prefixle_test_le_
Sends real emails❌✅
Rate limitsLowerStandard
AnalyticsLimitedFull

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Best Practices

API keys should only be used server-side. Never include them in frontend JavaScript.
Store keys in environment variables, not in code.
Create new keys and retire old ones periodically.
Only grant the permissions each key needs.

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List Your Keys

const keys = await lettr.apiKeys.list();

keys.forEach(key => {
  console.log({
    id: key.id,
    name: key.name,
    lastUsed: key.lastUsedAt,
    permissions: key.permissions
  });
});

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Revoke a Key

await lettr.apiKeys.delete('key_123');
Revoking a key is immediate and permanent. Any applications using the key will stop working.