OpenAI API with Express/TypeScript throws Missing credentials after moving API key to .env

Question

I’m building an app with NodeJs, Express and TypeScript.

At first, I hardcoded the OPENAI_API_KEY directly in my code for testing, and it worked fine. Now, I’ve moved the key to a .env file because I want to push the code to a repo, but I’m getting this error: OpenAIError: Missing credentials. Please pass an apiKey, or set the OPENAI_API_KEY environment variable.

I tried moving my hardcoded API key into a .env file and used dotenv to load it. I expected the OpenAI client to read the key from process.env.OPENAI_API_KEY and work normally. Instead, I got the error:Missing credentials. Please pass an apiKey, or set the OPENAI_API_KEY environment variable.

import OpenAI from "openai";

const openAIClient = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY,
});

type GenerateTextOptions = {
  model?: string;
  prompt: string;
  instructions?: string;
  temperature?: number;
  maxTokens?: number;
  previousResponseId?: string;
};

type GenerateTextResult = {
  id: string;
  text: string;
};

export const llmClient = {
  async generateText({
    model = "gpt-4.1",
    prompt,
    instructions,
    temperature = 0.2,
    maxTokens = 300,
    previousResponseId,
  }: GenerateTextOptions): Promise<GenerateTextResult> {
    const response = await openAIClient.responses.create({
      model,
      input: prompt,
      instructions,
      temperature,
      max_output_tokens: maxTokens,
      previous_response_id: previousResponseId,
    });

    return {
      id: response.id,
      text: response.output_text,
    };
  },
};

Mohammad Sh · Accepted Answer · 2025-09-26 13:46:14Z

0

The "Missing credentials" error occurs because the process.env.OPENAI_API_KEY is likely undefined at runtime, meaning your .env file isn't being loaded properly by dotenv. Ensure you import and call dotenv.config() early in your application entry point (e.g., app.ts or index.ts) before any modules that use the OpenAI client are imported or initialized. Also, verify your .env file is in the project root, contains OPENAI_API_KEY=your_actual_key (no quotes, no spaces), and isn't ignored by .gitignore. If using TypeScript, confirm dotenv is installed (npm i dotenv and npm i -D @types/node if needed).


// .env file (project root, not committed to repo)
OPENAI_API_KEY = sk - your - actual - key - here
// app.ts or index.ts (entry point)
import dotenv from 'dotenv';
dotenv.config();  // Load early, before OpenAI imports
import OpenAI from 'openai';
const openAIClient = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
// To debug: console.log('API Key loaded:', !!process.env.OPENAI_API_KEY); // Should log true if loaded
type GenerateTextOptions = {
  model?: string;
  prompt: string;
  instructions?: string;  // Use system message for instructions
  temperature?: number;
  maxTokens?: number;
  previousResponseId?: string;  // Not standard; consider session handling
};
type GenerateTextResult = { id: string; text: string };
export const llmClient = {
  async generateText({
    model = 'gpt-3.5-turbo',
    prompt,
    instructions,
    temperature = 0.2,
    maxTokens = 300,
    previousResponseId,  // Ignored in this example; implement if needed
  }: GenerateTextOptions): Promise & lt;GenerateTextResult& gt; {
  const messages = [
    ...(instructions ? [{ role: 'system', content: instructions }] : []),
    { role: 'user', content: prompt },
  ];
  const response = await openAIClient.chat.completions.create({
    model,
    messages,
    temperature,
    max_tokens: maxTokens,
  });
  return {
    id: response.id || '',
    text: response.choices[0]?.message?.content || '',
  };
},
};

answered Sep 26 at 13:46

Mohammad Sh

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2 Comments

Abid Sep 26 at 21:27

You are right in import dot env config. But you really aware expose envs in github?. You should add .env in .gitignore

Dan Crews Oct 10 at 21:36

Side note, if you're using any current version of Node.js, passing a --env-file has replaced dotenv. nodejs.org/docs/latest/api/environment_variables.html#env-files

theo - dmno · Accepted Answer · 2025-10-10 21:47:29Z

0

You can also try https://varlock.dev for an alternative to dotenv that will also give you validation and type safety. This will help ensure that env vars are all valid before anything else happens.

answered Oct 10 at 21:47

theo - dmno

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