Overview
The IsValid API is a REST API that returns JSON responses. All endpoints are available at the base URL:
https://api.isvalid.devAll requests must include a valid API key in the Authorization header. Responses include a valid boolean field indicating whether the provided value passed validation.
Authentication
Authenticate API requests using a Bearer token in the Authorization header. You can find your API key in your account dashboard.
Authorization: Bearer YOUR_API_KEYKeep your API key secret. Never expose it in client-side code or public repositories. Rotate your key immediately if you believe it has been compromised.
Example request
curl -H "Authorization: Bearer YOUR_API_KEY" \
"https://api.isvalid.dev/v0/email?value=user@example.com"Rate Limiting
API usage is limited based on your subscription plan. Rate limits reset at midnight UTC each day.
| Plan | API Keys | Calls / day | Price |
|---|---|---|---|
| Free | 1 | 100 | $0/month |
When you exceed your limit, the API returns HTTP 429. The response includes a Retry-After header indicating when your quota resets.
Error Responses
The API uses standard HTTP status codes. Error responses always include a JSON body with a message field describing the error.
| Status Code | Meaning | Description |
|---|---|---|
| 200 OK | Success | The request succeeded. Check the valid field in the response body. |
| 400 Bad Request | Invalid input | Missing or malformed required parameters. |
| 401 Unauthorized | Authentication failed | API key is missing, invalid, or expired. |
| 404 Not Found | Unknown endpoint | The requested endpoint does not exist. |
| 422 Unprocessable Entity | Validation schema error | The request body or parameters did not match the expected schema. |
| 429 Too Many Requests | Rate limit exceeded | You have exceeded your plan's daily request quota. |
| 500 Internal Server Error | Server error | An unexpected error occurred on our end. Retry after a moment. |
Error Response Body
{
"error": "Missing required query parameter: value"
}Official SDKs
Use our official SDKs for a simpler integration experience — they handle authentication, retries, and error handling out of the box.
See the Getting Started guide for Node.js / TypeScript or Python for a step-by-step integration walkthrough.
WordPress Plugin
The IsValid – Data Validation plugin connects any WordPress site to the isvalid.dev API without exposing your API key to the browser. It supports 80+ validator types and integrates with Contact Form 7, WooCommerce, Gravity Forms and WPForms.
Generic usage
<input data-isvalid="iban" />Shortcode
[isvalid_input type="iban" name="iban"]