Vietnamese Accent Restoration API

Restore Vietnamese diacritics in text typed without accents (“xin chao cac ban” → “xin chào các bạn”) using a dictionary and syllable frequencies.

POSTGEThttps://apibox.io.vn/v1/vn-diacritics

Text▶ Try it online

The accent restoration API turns Vietnamese typed without diacritics, common in SMS, chats, old databases and product names, back into proper Vietnamese: Ngan hang Nha nuoc vua giam lai suat → Ngân hàng Nhà nước vừa giảm lãi suất. Each run of unaccented words is solved as a whole with dynamic programming: the API prefers sequences that form dictionary words of two to four syllables, then the most frequent syllables.

Capitalisation is kept (Ha Noi → Hà Nội, CONG TY → CÔNG TY), punctuation and numbers are left alone, and words that are not Vietnamese stay unchanged. alternatives=1–5 lists, for every ambiguous syllable, the other likely readings, so an interface can let the user pick (ban: bạn / bán / bàn).

It runs on a word list and frequency tables, without an AI model, in a few milliseconds. Results are good for common phrases and names; short or unusual sentences can need a human check. Text that is already partly accented is fine: syllables typed with accents are kept as they are and help choose the accents of their neighbours.

Parameters

Name	In	Type	Required	Default
`text`	body\|query	string	yes		Unaccented Vietnamese text (max 20,000 characters).
`alternatives`	body\|query	number	no	`0`	Other readings to list per ambiguous syllable (0–5).

Example

curl -X POST "https://apibox.io.vn/v1/vn-diacritics" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"text":"Ngan hang Nha nuoc vua giam lai suat dieu hanh","alternatives":2}'

const res = await fetch('https://apibox.io.vn/v1/vn-diacritics', {
  method: 'POST',
  headers: {
    Authorization: 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "text": "Ngan hang Nha nuoc vua giam lai suat dieu hanh",
    "alternatives": 2
  }),
});
const data = await res.json();
console.log(data);

import requests

res = requests.post(
    "https://apibox.io.vn/v1/vn-diacritics",
    headers={"Authorization": "Bearer YOUR_API_KEY"},
    json={"text": "Ngan hang Nha nuoc vua giam lai suat dieu hanh", "alternatives": 2},
    timeout=30,
)
print(res.json())

<?php
$ch = curl_init('https://apibox.io.vn/v1/vn-diacritics');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_HTTPHEADER => ['Authorization: Bearer YOUR_API_KEY', 'Content-Type: application/json'],
    CURLOPT_POSTFIELDS => '{"text":"Ngan hang Nha nuoc vua giam lai suat dieu hanh","alternatives":2}',
]);
$response = curl_exec($ch);
print_r(json_decode($response, true));

Response

{
  "input": "Ngan hang Nha nuoc vua giam lai suat dieu hanh",
  "result": "Ngân hàng Nhà nước vừa giảm lãi suất điều hành",
  "syllables_changed": 10,
  "ambiguous_syllables": 8,
  "alternatives": [
    {
      "word": "Ngân",
      "position": 0,
      "options": [
        "ngân",
        "ngắn",
        "ngăn"
      ]
    },
    {
      "word": "vừa",
      "position": 19,
      "options": [
        "vừa",
        "vua",
        "vựa"
      ]
    },
    {
      "word": "lãi",
      "position": 28,
      "options": [
        "lai",
        "lại",
        "lãi"
      ]
    }
  ],
  "note": "Accents are chosen from a dictionary and syllable frequencies; ambiguous words (ban: bạn / bán / bàn) may need a human check."
}

Use cases

Fix product names and addresses imported without accents
Make SMS and chat messages readable
Restore accents in old database exports
Suggest accented text as the user types

FAQ

How accurate is it?

Common phrases come out right most of the time; ambiguous short words may be wrong, which is why alternatives are offered.

Does it use AI?

No, a dictionary of words and syllable frequencies with dynamic programming, so it is fast and deterministic.

Can I send text that already has some accents?

Yes. Syllables that already have accents are kept unchanged and only the unaccented ones are restored, e.g. “Hôm nay troi dep qua” → “Hôm nay trời đẹp quá”.

Vietnamese Accent Restoration API

Parameters

Example

Response

Use cases

FAQ

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