Anthropic Claude API Key Tester

Test any AI or API key in your browser — instantly see if it's valid, and why it isn't. Nothing is stored.

Test your Anthropic Claude API key with the messages endpoint

Data verified 2026-07-13

Key format & how to get one

Prefix: sk-ant-api03- Example: sk-ant-api03-abc...xyz Claude keys start with sk-ant-api03-. 1. Visit https://console.anthropic.com/ and sign up/login 2. Go to Account Settings > API Keys 3. Click 'Create Key' and provide a name 4. Copy the generated key (it won't be shown again) 5. Add $5+ credits to your account to use the API

How to test

  1. Copy your key from console.anthropic.com/settings/keys.
  2. Paste it into the tester above and click Test Key.
  3. Green means valid; red shows the exact status and how to fix it.

Common errors

CauseFix
Invalid x-api-key, or the key was revoked.Create a new key at console.anthropic.com/settings/keys and paste it here.
Your account has no API credit (credits can lag a purchase).Add credit at console.anthropic.com/settings/billing; wait a minute if you just purchased.
Rate or usage limit exceeded.Wait and retry, or request higher limits.

Anthropic Claude API docs →

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