AI API Key Tester

Not sure if your API key works? APIMaster's free API key tester lets you verify any OpenAI-compatible key—check validity, balance, and whether responses match expected model behavior.

Test Your API Key Now

Go to APIMaster.ai API Key Tester to test any key instantly in your browser—no signup required.

What the API Key Tester Checks

1. Key validity: is the key syntactically correct and accepted by the provider?
2. Account balance: does the account have funds for API calls?
3. Model access: which models does this key have permission to call?
4. Response verification: does the model response match expected behavior?

Test Your Key with Python

from openai import OpenAI

def test_api_key(api_key: str, base_url: str = "https://apimaster.ai/v1") -> dict:
    """Test an API key and return status info."""
    client = OpenAI(api_key=api_key, base_url=base_url)
    
    results = {}
    
    # Test 1: List models (lightweight check)
    try:
        models = list(client.models.list())
        results["valid"] = True
        results["model_count"] = len(models)
        results["models"] = [m.id for m in models[:5]]
    except Exception as e:
        results["valid"] = False
        results["error"] = str(e)
        return results
    
    # Test 2: Make a minimal API call
    try:
        response = client.chat.completions.create(
            model="gpt-4o-mini",
            messages=[{"role": "user", "content": "Reply with 'ok'"}],
            max_tokens=5,
        )
        results["callable"] = True
        results["response"] = response.choices[0].message.content
    except Exception as e:
        results["callable"] = False
        results["call_error"] = str(e)
    
    return results

# Test your key
result = test_api_key("YOUR_API_KEY")
print(result)

Testing for Claude API Key Validity

import anthropic

def test_claude_key(api_key: str, base_url: str = "https://apimaster.ai") -> bool:
    """Test a Claude (Anthropic) API key."""
    client = anthropic.Anthropic(api_key=api_key, base_url=base_url)
    try:
        response = client.messages.create(
            model="claude-haiku-4-5",
            max_tokens=5,
            messages=[{"role": "user", "content": "Say 'ok'"}],
        )
        print(f"✅ Key valid. Response: {response.content[0].text}")
        return True
    except anthropic.AuthenticationError:
        print("❌ Invalid key")
        return False
    except anthropic.APIStatusError as e:
        print(f"⚠️ API error: {e.status_code} - {e.message}")
        return False

test_claude_key("YOUR_CLAUDE_KEY")

Why API Keys Fail

Error	Meaning	Fix
401 Unauthorized	Key is invalid or expired	Get a new key from console
403 Forbidden	Key lacks permission for this model	Check key scope/tier
429 Too Many Requests	Rate limit hit	Wait or upgrade tier
402 Payment Required	Account has no balance	Top up account
400 Bad Request	Wrong base_url or request format	Check endpoint

Verify Claude Responses Match the Expected Model

Multi-model API services can make model provenance harder to inspect, including fake model or substitute-model risk. APIMaster's fingerprint detection system verifies model response patterns weekly.

How it works:

1. We send carefully crafted "fingerprint prompts" that target model-specific response patterns
2. We analyze response patterns to confirm model identity
3. Results are published publicly at https://apimaster.ai/ai-api-model-tester

# Quick manual test: does the model respond correctly to anthropic-specific prompts?
response = client.chat.completions.create(
    model="claude-sonnet-4-6",
    messages=[{"role": "user", "content": "Who made you? Reply in exactly 3 words."}],
)
# Expected Claude behavior is a response such as "Anthropic made me"
print(response.choices[0].message.content)

Batch Testing Multiple Keys

import concurrent.futures

def test_key_quick(key_info):
    api_key, label = key_info
    client = OpenAI(api_key=api_key, base_url="https://apimaster.ai/v1")
    try:
        client.models.list()
        return label, "✅ valid"
    except Exception as e:
        return label, f"❌ {type(e).__name__}"

keys_to_test = [
    ("sk-key1...", "Production"),
    ("sk-key2...", "Staging"),
    ("sk-key3...", "Testing"),
]

with concurrent.futures.ThreadPoolExecutor(max_workers=5) as pool:
    for label, status in pool.map(test_key_quick, keys_to_test):
        print(f"{label}: {status}")

Get a Verified API Key

If your current key isn't working—or you want model verification data alongside API access—get a key from APIMaster:

Frequently Asked Questions

How do I test if my API key works? The fastest way: open APIMaster's API Key Tester, enter your key and endpoint, and click Test. You'll see latency, token usage, and the model's response in seconds.

What causes an API key to fail with 401 Unauthorized? The key is wrong (typo, extra whitespace), expired, or tied to a different base URL. Re-copy it from your provider's console and double-check the base_url setting.

How do I know if my API key is getting the expected Claude model? Use APIMaster's AI API Model Tester. It runs fingerprint detection that compares Claude responses with expected model-specific behavior.

Can I test multiple API keys at once? Yes—use the batch testing script in the guide above, which runs tests in parallel and reports latency and success/failure for each key.

What is the difference between API key testing and model verification? API key testing checks connectivity and authentication. Model verification (fingerprinting) confirms the model behind the endpoint matches what's advertised—a different and more in-depth check.

Test your API key free → · Get verified API key → · View model verification data →