---
title: "CLOVA Speech Recognition (CSR) overview"
slug: "ai-naver-clovaspeechrecognition"
updated: 2026-09-17T09:35:47Z
published: 2026-09-17T09:35:47Z
canonical: "api.ncloud-docs.com/ai-naver-clovaspeechrecognition"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://api.ncloud-docs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# CLOVA Speech Recognition (CSR) overview

Available in Classic and VPC

CLOVA Speech Recognition is a NAVER Cloud Platform service that converts human speech into text. The CLOVA Speech Recognition service provides APIs in RESTful form for various voice recognition features utilized in assistant applications, chatbots, voice memos, and more. For mobile environments, it provides APIs in the form of Android and iOS SDKs to receive voice input from users.

              Note

              

CLOVA Speech allows you to upload long audio/video files to check the speech recognition results. On the other hand, the CSR (CLOVA Speech Recognition) service is optimized for imperative speech recognition within one minute.

## Common CLOVA Speech Recognition (CSR) settings

The following describes commonly used request and response formats in CLOVA Speech Recognition APIs.

### Request

The following describes the common request format.

#### API URL

The request API URL is as follows.

```
https://naveropenapi.apigw.ntruss.com/recog/v1
```

              Note

              

See the [Mobile SDK](/docs/en/ai-naver-clovaspeechrecognition-mobilesdk) documentation for platform-specific ways to use the APIs in a mobile environment.

#### Request headers

The following describes the request headers.

| Field | Required | Description |
| --- | --- | --- |
| `x-ncp-apigw-api-key-id` | Required | Client ID issued after application registration in NAVER Cloud Platform console |
| `x-ncp-apigw-api-key` | Required | Client secret issued after application registration in NAVER Cloud Platform console |
| `Content-Type` | Required | Request data format - `application/octet-stream` |

              Note

              

For information on how to register an application in the NAVER Cloud Platform console to obtain authentication information (client ID, client secret) required to use the API, see [CLOVA Speech Recognition (CSR) User Guide](https://guide.ncloud-docs.com/docs/en/csr-application). In the console, make sure that the API you want to use after registering the application is selected by clicking the **[Edit]** button. If it is not selected, you will receive a 429 (Quota Exceed) error.

### Response

The following describes the common response format.

#### Response status codes

The following describes the response status codes.

- STT (Speech-to-Text)

| HTTP status code | Code | Message | Description |
| --- | --- | --- | --- |
| 413 | STT000 | Request Entity Too Large | Entered voice data value exceeds the allowed capacity (up to 3 MB) |
| 413 | STT001 | Exceed Sound Data length | Entered voice data value exceeds the allowed length (up to 60 seconds) |
| 400 | STT002 | Invalid Content Type | `Content-Type` other than `application/octet-stream` is entered |
| 400 | STT003 | Empty Sound Data | No voice data entered |
| 400 | STT004 | Empty Language | Language (`lang`) parameter not entered |
| 400 | STT005 | Invalid Language | Entered language (`lang`) parameter not supported |
| 500 | STT006 | Failed to pre-processing | Error during speech recognition preprocessing - Need to ensure voice data is legitimate `wav`, `mp3`, or `flac` file |
| 400 | STT007 | Too Short Sound Data | Voice data is too short (400 ms or less) |
| 500 | STT998 | Failed to STT | Error during speech recognition - Contact Support |
| 500 | STT999 | Internal Server Error | Internal server error - Contact Support |

- Mobile SDK

| HTTP status code | Code | Message | Description |
| --- | --- | --- | --- |
| - | 10 | ERROR_NETWORK_INITIALIZE | Error resetting network resources |
| - | 11 | ERROR_NETWORK_FINALIZE | Error releasing network resources |
| - | 12 | ERROR_NETWORK_READ | Error receiving network data - Timeout due to slow network environment on client device |
| - | 13 | ERROR_NETWORK_WRITE | Error sending network data - Timeout due to slow network environment on client device |
| - | 14 | ERROR_NETWORK_NACK | Error on speech recognition server - Timeout due to slow network environment on the client device not sending voice packets to the server in time |
| - | 15 | ERROR_INVALID_PACKET | Error due to sending invalid packets |
| - | 20 | ERROR_AUDIO_INITIALIZE | Error resetting audio resources - Need to verify audio permissions |
| - | 21 | ERROR_AUDIO_FINALIZE | Error releasing audio resources |
| - | 22 | ERROR_AUDIO_RECORD | Error during voice input (recording) - Need to verify audio permissions |
| - | 30 | ERROR_SECURITY | Authentication permission error |
| - | 40 | ERROR_INVALID_RESULT | Recognition result error |
| - | 41 | ERROR_TIMEOUT | Failed to send voice to the server for a period of time or didn't receive recognition results |
| - | 42 | ERROR_NO_CLIENT_RUNNING | Detected certain speech recognition-related event in situation where client is not performing speech recognition |
| - | 50 | ERROR_UNKNOWN_EVENT | Detected undefined event inside the client |
| - | 60 | ERROR_VERSION | Protocol version error |
| - | 61 | ERROR_CLIENTINFO | Client information error |
| - | 62 | ERROR_SERVER_POOL | Not enough servers available for speech recognition |
| - | 63 | ERROR_SESSION_EXPIRED | Speech recognition server session expired |
| - | 64 | ERROR_SPEECH_SIZE_EXCEEDED | Speech packet size exceeded |
| - | 65 | ERROR_EXCEED_TIME_LIMIT | Error in timestamp for authentication |
| - | 66 | ERROR_WRONG_SERVICE_TYPE | Invalid service type |
| - | 67 | ERROR_WRONG_LANGUAGE_TYPE | Invalid language type |
| - | 70 | ERROR_OPENAPI_AUTH | Error when authenticating with Open API - Invalid client ID and registered package name (Android) or Bundle ID information (iOS) |
| - | 71 | ERROR_QUOTA_OVERFLOW | Exhausted a set API call limit (quota) |

- Other errors and inquiries

| Phenomenon or inquiry | Cause or solution |
| --- | --- |
| UnsatifiedLinkError occurred | - The CSR API provides libraries built with armeabi and armeabi-v7a - If any of the libraries used by the app you're developing don't support armeabi and armeabi-v7a, you may encounter this error |
| android fatal signal 11 (sigsegv) error occurred | - Must prepare resources before accepting voice input using the CSR API - Make sure `initialize()` and `release()` are called before calling `recognize()` |
| `""(null)` returned as recognition result | - Can occur if the user speaks in a very low voice, or if the voice is not recognized due to ambient noise - Although it is extremely rare, it is recommended to throw an exception when the recognition result is null (empty) |
| Audio file recognition | CSR API does not support audio file recognition |
| Does not work well on low-end smartphones | Android SDK version 10 or higher, iOS version 8 or higher devices supported |

              Note

              

For response status codes common to NAVER Cloud Platform, see [Ncloud API response status codes](/docs/en/common-ncpapi#3%EC%9D%91%EB%8B%B5%EC%83%81%ED%83%9C%EC%BD%94%EB%93%9C).

## CLOVA Speech Recognition API

The following describes the APIs provided by the CLOVA Speech Recognition service.

| API | Description |
| --- | --- |
| [STT (Speech-to-Text)](/docs/en/ai-naver-clovaspeechrecognition-stt) | Extract speech to text |
| [Mobile SDK](/docs/en/ai-naver-clovaspeechrecognition-mobilesdk) | Extract speech to text in mobile environment |

## CLOVA Speech Recognition related resources

NAVER Cloud Platform provides a variety of related resources to help users better understand CLOVA Speech Recognition APIs.

- CLOVA Speech Recognition API guides
  - [API overview](/docs/en/common-ncpapi): how to issue and check access key and secret key issued by NAVER Cloud Platform, how to generate the signature required for request headers
  - [API Gateway User Guide](https://guide.ncloud-docs.com/docs/en/apigw-apigw-1): how to check the API key required for the request header
  - [Common Ncloud response status codes](/docs/en/common-ncpapi#3-%EC%9D%91%EB%8B%B5-%EC%83%81%ED%83%9C-%EC%BD%94%EB%93%9C): information on common response status codes of NAVER Cloud Platform used by the CLOVA Speech Recognition service
- How to use the CLOVA Speech Recognition service
  - [CLOVA Speech Recognition User Guide](https://guide.ncloud-docs.com/docs/en/csr-overview): how to use CLOVA Speech Recognition in the NAVER Cloud Platform console
  - [Ncloud use environment guide](https://guide.ncloud-docs.com/docs/en/environment-environment-1-1): guide for VPC and Classic environments and support availability
  - [Introduction to pricing, characteristics, and detailed features](https://www.ncloud.com/product/aiService/csr): the summary of pricing system, characteristics, and detailed features of CLOVA Speech Recognition
  - [Latest service news](https://www.ncloud.com/intro/news): the latest news on CLOVA Speech Recognition
  - [FAQ](https://www.ncloud.com/support/faq/prod?categoryCode2=APP&categoryCode3=SV_0067): frequently asked questions from CLOVA Speech Recognition users
  - [Contact Us](https://www.ncloud.com/support/question/service): Send direct inquiries in case of any unresolved questions that aren't answered by the user guides.