---
title: "Check whether a username is still available before registering."
method: POST
path: "/v1/check_username"
tags: ["Authentication"]
---

# Check whether a username is still available before registering.

`POST /v1/check_username`

## Request

- Base URL: `https://partner.mindupload.app`
- URL: `https://partner.mindupload.app/v1/check_username`
- Auth: API key in header `X-Partner-Key`

## Request body

- object
  - `preferred_language` string, nullable: BCP-47-ish language code (e.g. 'en', 'zh-cn') for localized messages.
  - `username` string, nullable: The end-user's username.

## Response `200`

Result envelope — check the success field.

- object
  - `success` boolean: Whether the call succeeded.
  - `error_message` string, nullable: Human-readable reason when success is false.
  - `error_code` string
  - `exists` boolean, nullable
  - `disabled` boolean, nullable
  - `rate_limited` boolean, nullable
  - `flood_window` string, nullable
  - `wait_seconds` integer, nullable
  - `operation_duration_ms` number, nullable: Server-side duration of the operation in milliseconds.

## Other responses

- `400`: Invalid request payload.
- `401`: Missing or invalid partner key.
- `403`: Partner is not authorized for this operation.
- `429`: Rate limit exceeded — retry later.
- `500`: Internal server error.

---

[API](https://skmtc.dev/mindupload/apis/mind-upload-partner-api.md) · [All operations](https://skmtc.dev/mindupload/apis/mind-upload-partner-api/llms.txt) · [OpenAPI document](https://skmtc.dev/mindupload/apis/mind-upload-partner-api/revisions/0371bdf78533?raw)