> For the complete documentation index, see [llms.txt](https://manual.trancy.org/en/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://manual.trancy.org/en/get-started/use-extension/custom-translation-engine.md).

# Custom Translation Engine

Trancy lets you choose how your subtitles and pages are translated. Free plans use the Google and Microsoft engines; Premium adds higher-quality AI models such as GPT, Claude, Gemini, and DeepSeek; and a custom engine option lets you connect your own API key for supported providers.

###  Supported translation engines

* Base engines (free plan): Google and Microsoft machine translation.
* DeepL: a dedicated high-quality translation engine.
* AI translation engines (Premium): OpenAI (GPT), Claude, Gemini, DeepSeek, Meta, and Grok. Premium bundles ready-to-use models such as GPT-5-mini, GPT-4.1 mini, DeepSeek V3, Claude 4.5 Haiku, and Gemini 2.0 Flash.
* Custom engine (bring your own key): connect your own API key for a supported provider to use your own account and quota. See "Add a custom API" below.

### Add custom API

1\. Click "Translation Engine" -> "Custom API". 

2\. Select the desired engine category, enter the custom name and API KEY. 

3\. Click the "Add" button, verify and save successfully. 

4\. Return to the "Translation Engine" settings page and switch to the added custom engine.

### FAQ

<details>

<summary><mark style="color:red;">Why does OpenAI only support full-text and sentence translation, and not subtitle translation?</mark></summary>

Open AI has been spending a lot of time on subtitle translation with unsatisfying results, and we are still trying to find a better solution. The main reason for inaccurate subtitle translation is due to sentence breaking. If the sentence breaking is optimized, the effect of using a custom translation engine will be better. We are still in the process of optimization, and we appreciate your understanding and support.

</details>

**What is the monthly AI engine quota, and what happens if I run out?**

Premium includes a large monthly allowance of AI translation tokens (a Translation Engine Package). If you use it up, Trancy keeps working on the free Google and Microsoft engines, and you can buy an additional AI engine package or connect your own API key with a custom engine.

*Last updated: June 5, 2026.*