Free SRT Subtitle Translator Using Gemini AI: No Paid API Key Required

Are you tired of AI-translated subtitles that drift out of sync?

We’ve all been there. You use a powerful LLM to translate a movie or TV show, but the result is a mess. The timestamps shift, the AI hallucinates characters from the wrong language, or it simply stops halfway through.

Today, I’m sharing a game-changing, open-source workflow that solves these problems completely. It combines the power of Google Gemini with a smart SRT Validator to give you perfect, studio-quality subtitles for free.

Why This Tool is a Game Changer

Most AI translation tools require expensive API subscriptions or manual copy-pasting. This setup is different.

By leveraging CLIProxyAPI and the SRT Translator & Validator, you can:

• Access Gemini Pro for Free: Utilize your personal Google account’s free tier quota (no billing account required).
• Eliminate Timestamp Drift: The tool automatically aligns the translated subtitles with the source timestamps.
• Prevent “Hallucinations”: It strictly validates the output script (e.g., ensuring a Vietnamese subtitle file doesn’t randomly contain Chinese or Thai characters).
• Resume Capability: If the AI stops mid-file, the tool picks up exactly where it left off.

The Tech Stack (How it Works)

This workflow uses two open-source components:

1. CLIProxyAPI: A bridge that turns your local terminal into an API server, allowing you to access Gemini models via the web interface without complex OAuth setups.
2. SRT Translator & Validator: A browser-based UI that handles the logic: uploading files, sending prompts, validating the text, and fixing errors.

Step-by-Step Guide: Translate Subtitles for Free

Step 1: Install CLIProxyAPI

First, you need the bridge to talk to Google Gemini.

For macOS (via Homebrew):

brew install router-for-me/tap/cliproxyapi

Login to Gemini:

This command opens your browser to authenticate with Google. Tip: Use a Google Cloud Project with no billing attached to ensure it stays free.

cliproxyapi --login

Step 2: Start the Local Server

Run the proxy server on your machine.

cliproxyapi
# Server starts at http://localhost:8317

Step 3: Open the Translator Dashboard

Open the index.html on project folder

Since the app runs entirely in your browser (client-side), your data remains private and connects directly to your local CLIProxyAPI server.

Step 4: Configure & Translate

1. API Key: Enter the key from your CLIProxy config (or use dummy if you haven’t set a strict key locally).
2. Allowed Scripts: Select your target language (e.g., Japanese, Spanish) to prevent character errors.
3. Upload: Drag and drop your English .srt file.
4. Prompt: Use the built-in template or customize your own:”Translate this subtitle from English to Vietnamese. Keep the tone casual and natural.”
5. Click Translate.

Step 5: Validate and Fix

Once finished, the tool will highlight any errors (red lines).

• Timestamp Errors: Click “Fix All Errors” to snap timestamps back to the original source.
• Script Errors: The tool will automatically send bad lines back to Gemini for re-translation.

Why Is This Better Than ChatGPT Plus?

Conclusion

This is currently the most robust method to generate localized subtitles for movies, educational content, or YouTube videos without spending a dime. It combines the reasoning power of Gemini 2.5/3.0 with the strict logic of a code-based validator.

Ready to vibe code your subtitles?

Get the Tool on GitHub

Happy Subtitling!