Do I need to sign up to use the NSFW Checker API?

No. The free tier works without any account, API key, or signup. You get 100 requests per day, rate limited by your IP address. Just send a POST request with an image to https://api.nsfwcheckers.workers.dev and get a JSON result with a safe/unsafe classification and confidence score.

What image formats does the NSFW detection API support?

The API supports JPEG, PNG, WebP, and GIF images up to 10MB in size. Send the image as multipart/form-data with the field name 'image', or as a raw binary request body. Both methods produce identical results. The API automatically detects the image format.

Are uploaded images stored or logged?

No. All images are processed entirely in memory on edge workers and immediately discarded after classification. Nothing is written to disk, stored in a database, or logged. We have no ability to retrieve, review, or access any image after processing. See our privacy policy at nsfwcheckers.com/privacy for full details.

How accurate is the NSFW detection?

The API uses Microsoft's ResNet-50 deep learning model, a 50-layer convolutional neural network trained on millions of labeled images from ImageNet. It reliably detects nudity, swimwear, lingerie, and explicit content. The confidence score (0 to 1) lets you set your own threshold — lower for stricter moderation, higher for more permissive. Like all AI models, edge cases with suggestive but clothed content may vary.

What happens when I reach the daily API limit?

You receive a 429 (Too Many Requests) HTTP status code with a JSON response containing your current usage count, remaining quota, and daily limit. The limit resets at midnight UTC every day. You can monitor your usage in real-time using the 'used' and 'remaining' fields in every API response.

Can I use the NSFW Checker API in commercial projects?

Yes. All plans including the free tier are available for commercial use in production applications. No attribution is required. You can integrate it into any app, website, platform, or service. The API is suitable for social media platforms, dating apps, image hosting services, forums, and AI image generators.

When will paid plans be available?

Pro (5,000 requests/day at $9/month) and Business (50,000 requests/day at $29/month) plans are coming soon. Both will include dedicated API keys, priority processing, and a usage dashboard. The free tier with 100 requests per day is fully available now with no restrictions.

What Is an NSFW Detection API and How Does It Work?

Learn how NSFW detection APIs use deep learning to classify images as safe or unsafe. Understand the technology behind automated content moderation.

NSFW Checker Team

April 7, 2026 · 5 min read

What is NSFW detection?

NSFW (Not Safe For Work) detection is the process of automatically identifying images that contain nudity, explicit content, or other material that is inappropriate for general audiences. It is a critical component of content moderation for any platform that accepts user-uploaded images.

How does an NSFW detection API work?

An NSFW detection API accepts an image as input and returns a classification result. Under the hood, it uses a deep learning model — typically a convolutional neural network (CNN) — trained on millions of labeled images to recognize patterns associated with explicit content.

Here is the typical flow:

1. **Image upload** — Your application sends an image to the API endpoint via HTTP POST

2. **Preprocessing** — The image is resized and normalized for the neural network

3. **Inference** — The model analyzes the image and produces classification scores

4. **Response** — The API returns a JSON response with a boolean (safe/unsafe) and a confidence score

What model does NSFW Checker use?

NSFW Checker uses Microsoft's ResNet-50 (Residual Network with 50 layers), a deep convolutional neural network originally trained on the ImageNet dataset. It runs on a global edge network, which means inference happens on 300+ global edge locations for sub-500ms response times.

The model detects categories including:

Nudity: — Full or partial nudity

Swimwear: — Bikinis, swimsuits, beach content

Lingerie: — Underwear and intimate apparel

Explicit content: — Pornographic material

Why use an API instead of building your own?

Building and maintaining your own NSFW detection system requires:

Training data (millions of labeled images)

GPU infrastructure for training and inference

Ongoing model maintenance and retraining

Compliance with data handling regulations

An API like NSFW Checker handles all of this for you. You send an image, get a result, and the image is never stored. It takes 30 seconds to integrate versus months of building your own solution.

How to get started

Send a POST request with an image to the NSFW Checker API:

curl -X POST https://api.nsfwcheckers.workers.dev -F "image=@photo.jpg"

The response tells you whether the image is safe or not:

{
  "nsfw": false,
  "score": 0.02,
  "daily_limit": 100,
  "used": 1,
  "remaining": 99
}

No signup, no API key, 100 free requests per day.