Google Gemini API 403 PERMISSION_DENIED: what it means and how to fix it

403 PERMISSION_DENIED: Your project has been denied access

How to fix it

1. Check the project's status in Google AI Studio. Free-tier eligibility is per Google Cloud project, so a new key in the same project will not help; link a Cloud Billing account.
2. If billing is past due, fix the payment method.

Handle it in code

import random, time
from google import genai
from google.genai import errors

client = genai.Client()

def generate(prompt, tries=6):
    for i in range(tries):
        try:
            return client.models.generate_content(model="gemini-flash-latest", contents=prompt)
        except errors.APIError as e:
            # 429 RESOURCE_EXHAUSTED, 503 UNAVAILABLE, 500, 504: transient. 400/402/403: fix, do not retry.
            if e.code not in (429, 500, 503, 504) or i == tries - 1:
                raise
            time.sleep(min(60, 2 ** i) + random.random())  # exponential backoff + jitter

Google lists 429 RESOURCE_EXHAUSTED, 503 UNAVAILABLE, 408 and 5xx as transient: retry with exponential backoff and jitter. 400, 402 and 403 are not.

Same kind of error at other providers

• Anthropic 401 authentication_error
• Anthropic 403 permission_error
• OpenAI 401 invalid_api_key
• OpenAI 401 invalid_authentication

Other Google Gemini API errors

• 429RESOURCE_EXHAUSTEDretry
• 503UNAVAILABLE: The model is overloaded. Please try again later.retry
• 400INVALID_ARGUMENTfix
• 400FAILED_PRECONDITIONfix
• 402payment_requiredfix
• 403PERMISSION_DENIED: Your API key was reported as leaked. Please use another API key.fix
• 404NOT_FOUNDfix
• 500INTERNALretry
• 504DEADLINE_EXCEEDEDretry
• -RECITATIONfix
• -SAFETYfix

Source

• Google Gemini API error documentation: ai.google.dev/gemini-api/docs/api-errors (checked Oct 24, 2026)

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