Merge diataxis-variant-guide branch

Author: Parvati-DeepL

docs/learning-how-tos/examples-and-guides/translating-between-variants.mdx

@@ -1,50 +1,132 @@
 ---
 title: "Translating Between Language Variants"
-description: "Learn how to translate between variants of the same language, such as en-US to en-GB"
+description: "Learn how to translate between language variants, like British English and US English, using the DeepL API."
 public: true
 ---
 
-The DeepL API can translate between variants of the same language (for example, from pt-PT to pt-BR or from en-US to en-GB) using a few methods:
+**This guide shows you:**
+- How to translate between language variants (e.g., `en-US` to `en-GB`, `pt-PT` to `pt-BR`)
+- Which method to choose: Write API, style rules, or custom instructions
+- An example workflow for converting American English to British English
 
-- **[Write/Rephrase endpoint](/api-reference/improve-text)**: Rephrases text into the target language variant. This method is fully supported.
+---
 
-<Info> 
-Please note that currently, the methods outlined below are not fully supported for this use case and may not always perform as intended. We encourage you to conduct your own evaluations.
+## Methods for translating between variants
 
-Both glossaries and style rules are unique to each of DeepL's global data centers and are not shared between them. Clients using the api-us.deepl.com endpoint will not be able to access glossaries or style rules created in the UI at this time. 
-</Info>
+You can use the DeepL API to translate between variants of the same language using 3 methods:
+
+### 1. DeepL Write API
+
+Use the [/write/rephrase](/api-reference/improve-text) endpoint to rephrase text into the target language variant.
+
+**When to use this:**
+- You're translating shorter texts (headlines, product names, brief descriptions)
+- You want high-quality rephrasing alongside variant translation
+
+```bash Example cURL request
+curl -X POST 'https://api.deepl.com/v2/write/rephrase' \
+--header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
+--header 'Content-Type: application/json' \
+--data '{
+  "text": ["Check out the new fall colors!"],
+  "target_lang": "en-GB"
+}'
+```
+
+```json Example response
+{
+  "improvements": [
+    {
+      "text": "Check out the new autumn colours!",
+      "detected_source_language": "en",
+      "target_language": "en-GB"
+    }
+  ]
+}
+```
 
-- **[Style rules](/api-reference/style-rules)**: Create a custom style rule in the UI such as “translate to British English” and apply it using the [style_id](/api-reference/translate/request-translation#body-style-id) parameter.
+<Warning>
+For longer texts, the Write API may rephrase and enhance content beyond simple variant conversion. If you need to maintain the exact structure while only updating locale-specific spelling and grammar, use another method.
+</Warning>
 
-- **[Custom instructions](/api-reference/translate/request-translation#body-custom-instructions)**: Add instructions like "translate to British English" to your `/translate` request. You can specify up to 10 custom instructions in conjunction, each with a maximum of 300 characters.
+### 2. Style rules with custom instructions
 
-## Example: Converting American English to British English using the custom_instructions parameter:
+Create a reusable [style rule](/api-reference/style-rules) with attached `custom_instructions` describing the desired variant translation.
 
-Example request
-```bash
+**When to use this:**
+- You need to maintain the text's content between variants as precisely as possible
+- You need consistent variant transformations across many translation requests
+- You want to reuse the same variant rules without repeating the custom instructions
+
+```bash Example cURL request
 curl -X POST 'https://api.deepl.com/v2/translate' \
+--header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
 --header 'Content-Type: application/json' \
+--data '{
+  "text": ["I went to the pharmacy."],
+  "target_lang": "en-GB",
+  "style_id": "your-style-rule-id"
+}'
+```
+
+```json Example response
+{
+  "translations": [
+    {
+      "detected_source_language": "EN",
+      "text": "I went to the chemist's."
+    }
+  ]
+}
+```
+
+<Info>
+Glossaries and style rules are unique to each of DeepL's global data centers and are not shared between them.
+
+Clients using the `api-us.deepl.com` endpoint will not be able to access glossaries or style rules created in the UI at this time.
+</Info>
+
+### 3. Per-request custom instructions
+
+Add [custom_instructions](/api-reference/translate/request-translation#body-custom-instructions) describing the desired variant translation directly into your `/translate` requests.
+
+**When to use this:**
+- You need to maintain the text's content between variants as precisely as possible
+- You need ad-hoc, one-off translations with specific variant requirements
+- You don't want to manage separate style rules
+
+```bash Example cURL request
+curl -X POST 'https://api.deepl.com/v2/translate' \
 --header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
+--header 'Content-Type: application/json' \
 --data '{
-  "text": ["I went to the pharmacy to get some acetaminophen."],
+  "text": ["I went to the pharmacy."],
   "target_lang": "en-GB",
-  "model_type": "quality_optimized",
-  "custom_instructions": ["translate to British English", "only replace words that would be different"]
+  "custom_instructions": ["translate to British English"]
 }'
 ```
 
-Example response
-```json 
+```json Example response
 {
   "translations": [
     {
       "detected_source_language": "EN",
-      "text": "I went to the chemist to get some paracetamol.",
-      "model_type_used": "quality_optimized"
+      "text": "I went to the chemist's."
     }
   ]
 }
 ```
 
-<Tip>The custom instructions convert American English terms ("pharmacy", "acetaminophen") to British English equivalents ("chemist", "paracetamol") while preserving sentence structure.</Tip>
+You can specify up to 10 custom instructions per request, each with a maximum of 300 characters.
+
+---
+
+## Next steps
+
+Now that you understand how to translate between language variants:
+
+- **Try it yourself:** Test out style rules and custom instructions in the [text translation API playground](/api-reference/translate)
+- **Learn about the Write API:** Explore the [/write/rephrase endpoint](/api-reference/improve-text) for high-quality variant translation and rephrasing
+- **Manage reusable rules:** Learn how to create [style rules](/api-reference/style-rules) for systematic variant transformations
+- **Improve translation quality:** Understand how [the context parameter](/docs/best-practices/working-with-context) can enhance ambiguous translations