DeepL

What is DeepL?

DeepL is the official paid translation API from DeepL. In Read Frog, it is separate from DeepLX:

• DeepL uses DeepL's official API and requires a valid DeepL API key.
• DeepLX is an unofficial DeepL-like API with customizable Base URL behavior.

If you want the official DeepL service, choose DeepL in the API Providers page.

How Read Frog Configures DeepL

DeepL setup in Read Frog is intentionally simple:

• API Key: required
• Base URL: not shown and not configurable

Read Frog decides the correct DeepL endpoint from your API key automatically:

• Keys ending with :fx use https://api-free.deepl.com
• All other keys use https://api.deepl.com

You do not need to manually choose between Free and Pro endpoints.

Setting Up DeepL in Read Frog

1. Open the Read Frog extension options.
2. Go to API Providers.
3. Select Official DeepL API.
4. Paste your DeepL API key into the API Key field.
5. Test a translation.

That is all you need. There is no Base URL field for DeepL.

Free vs Pro DeepL Keys

Read Frog uses the API key format to decide which DeepL endpoint to call.

DeepL Free

If your key ends with :fx, Read Frog sends requests to:

https://api-free.deepl.com/v2/translate

DeepL Pro

If your key does not end with :fx, Read Frog sends requests to:

https://api.deepl.com/v2/translate

Language Handling

Read Frog adapts some language codes automatically for DeepL:

• Target zh becomes ZH-HANS
• Target zh-TW becomes ZH-HANT
• Source zh-TW is normalized to ZH
• When source language is set to auto, Read Frog lets DeepL detect it automatically

Troubleshooting

"DeepL API key is not configured"

Your API key field is empty. Add a valid DeepL API key in the provider settings.

"DeepL translation request failed"

Usually this means one of the following:

• The API key is invalid
• The API key type does not match your DeepL plan
• The DeepL service rejected the request

Free key not working

Make sure your DeepL Free key still ends with :fx. Read Frog uses that suffix to select the Free API endpoint.

When to Use DeepL vs DeepLX

Choose DeepL if you want:

• The official DeepL API
• Automatic Free/Pro endpoint handling
• A simpler setup with only an API key

Choose DeepLX if you want:

• A custom or self-hosted DeepLX provider
• Custom Base URL patterns
• {{apiKey}} placeholder support inside the URL