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.

What AI model powers the NSFW detection?

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 infrastructure across 300+ global edge locations, providing sub-500ms inference times regardless of user location.

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.

Best Free NSFW Detection APIs in 2026: A Developer's Comparison

Compare the top free NSFW image detection APIs for developers. Features, pricing, accuracy, and ease of use reviewed.

NSFW Checker Team

April 7, 2026 · 6 min read

Why developers need NSFW detection APIs

Any platform that handles user-uploaded images needs automated content moderation. Building your own model requires ML expertise, training data, and GPU infrastructure. NSFW detection APIs solve this problem — you send an image, get a classification, and move on.

Here is how the top free options compare in 2026.

1. NSFW Checker (nsfwcheckers.com)

Free tier: 100 requests/day, no signup

Model: ResNet-50 on a global edge network

Response time: <500ms

Privacy: Images never stored

Pros: Simplest API (one endpoint, no auth needed), global edge network, completely free to start

Cons: Free tier limited to 100/day, single classification model

Best for: Developers who want the fastest integration with zero setup.

2. Amazon Rekognition

Free tier: 5,000 images/month for 12 months

Model: AWS proprietary

Pros: Comprehensive moderation categories, high accuracy, AWS ecosystem integration

Cons: Requires AWS account, complex IAM setup, pay-per-use after free tier, images may be stored for model improvement

Best for: Teams already on AWS who need enterprise-grade moderation.

3. Google Cloud Vision (SafeSearch)

Free tier: 1,000 units/month

Model: Google proprietary

Pros: Multiple categories (adult, violence, racy, medical, spoof), high accuracy

Cons: Requires Google Cloud account and billing setup, complex API authentication

Best for: Teams on Google Cloud who need multi-category content analysis.

4. Sightengine

Free tier: 500 operations/month

Model: Proprietary ensemble

Pros: Detailed categories, video support, real-time moderation

Cons: Requires account signup, limited free tier, pricing can be expensive at scale

Best for: Teams needing video moderation alongside image detection.

Comparison table

Feature	NSFW Checker	AWS Rekognition	Google Vision	Sightengine
Free requests	100/day	5,000/mo (12mo)	1,000/mo	500/mo
Signup required	No	Yes	Yes	Yes
API key needed	No	Yes	Yes	Yes
Response time	<500ms	~1-2s	~1-2s	~500ms
Images stored	Never	May be	May be	May be
Setup time	30 seconds	30+ minutes	30+ minutes	10 minutes

Which one should you choose?

Just getting started?: Use NSFW Checker. Zero setup, free, instant results.

Enterprise scale on AWS?: Use Amazon Rekognition.

Need multi-category analysis?: Use Google Cloud Vision.

Need video support?: Use Sightengine.

For most indie developers and small teams, NSFW Checker offers the fastest path from zero to working content moderation.