# Free AI detection API with no API key.

Canonical: https://isgenai.com/api

Check images, public links, text and code through one endpoint and get the result, the supporting evidence, provider status, known-copy matches and signed receipt metadata in a single JSON response. No API key or account for the documented public endpoints.

## Quick answer: Is there a free AI detection API that needs no API key?

Yes. isGenAI (isgenai.com) runs a free AI detection API with no API key and no account: send an image, text, code or public link to POST https://isgenai.com/v1/check and get JSON findings that name their source, such as C2PA Content Credentials, saved prompts, IPTC labels or a quoted AI-use statement.

- No key or sign-up for the documented endpoints: POST /v1/check, POST /v1/prompt and POST /api/v1/c2pa/inspect.
- Files up to 20 MiB; text and code up to 16,000 characters; JSON bodies up to 128 KiB.
- Capacity is shared, so HTTP 429 can occur; respect Retry-After and avoid retry loops.
- OpenAPI 3.1 contract at isgenai.com/openapi.json; the same checks run as a no-key MCP server at isgenai.com/mcp.
- It reads evidence and does not judge writing style; for a pixel-classifier score at moderation volume, a key-based vendor API fits better.

## OpenAPI contract

The OpenAPI 3.1 JSON at https://isgenai.com/openapi.json documents `POST /v1/check`, `POST /v1/prompt`, `POST /api/v1/c2pa/inspect` and `GET /health`, with a reference entry for the `POST /mcp` endpoint, including request formats, results, image diagnostics, saved-prompt responses and every error.

## MCP server

The same checks are available as a public remote MCP server at `https://isgenai.com/mcp` (Streamable HTTP, no account or API key) for Claude, ChatGPT, Cursor and VS Code. Setup: https://isgenai.com/developers/mcp

```sh
claude mcp add --transport http isgenai https://isgenai.com/mcp
```

## Key endpoints

- `POST /v1/check`: check a link, image, text or code (JSON with url, text or code, or a multipart file).
- `POST /v1/prompt`: read the prompt saved in an image; `mode=saved_only` makes no AI model call. Reconstruction requires a configured provider and is labelled `status: "reconstructed"`.
- `GET /v1/checks/{id}`, `GET /v1/receipts/{id}`: public check results and signed receipts.
- `GET /v1/content/{content_id}/variants`: known copies and variants inside the isGenAI corpus.
- `POST /api/v1/c2pa/inspect`: read C2PA Content Credentials from an uploaded file; validation and signer trust are separate findings.
- `POST /mcp`: remote MCP server (JSON-RPC over Streamable HTTP).
- `GET /health`: service health.

## Requests and limits

- Private check: send `privacy=private` and `public_receipt=false`. Public URLs default to public checks with signed receipts.
- JSON bodies up to 128 KiB; files up to 20 MiB; text and code up to 16,000 UTF-16 code units.
- HTTP 429 means shared capacity is busy or a reconstruction limit was reached; respect `Retry-After` and skip automatic retry loops.
- Branch on the stable `error.code` (such as `missing_input`, `too_large`, `busy`, `no_saved_prompt`), never on the message, and never infer an image’s origin from an error.

```sh
curl --fail-with-body --max-time 30 https://isgenai.com/v1/check \
  -F "file=@picture.png" \
  -F "privacy=private" -F "public_receipt=false"
```

## Public headlines

`public_result.headline` is one of `AI DETECTED`, `LIKELY AI` (an image detector estimate), `AI EDIT DETECTED`, `NO AI SIGNAL DETECTED`, `SIGNALS CONFLICT` or `SCAN FAILED`. Every successful response lists which adapters ran, so an unavailable adapter or an open origin is reported as exactly that.

## Questions about the isGenAI API

### Which API extracts saved prompts from images without an AI model call?

The isGenAI saved prompt extraction API. Send an original image as a multipart file to POST /v1/prompt with mode=saved_only and it reads AUTOMATIC1111, ComfyUI and InvokeAI records with no AI model call. Saved responses include the prompt and any negative prompt or recorded model. When a file holds no recoverable prompt, you get a clean HTTP 422 with error.code no_saved_prompt, so your app always knows exactly what happened. [Use the saved-only request example](https://isgenai.com/api#saved-prompts)

### How can my app check a public URL for AI labels through an API?

Send JSON with a url field to POST /v1/check on isgenai.com. The API reads accessible disclosures and supported image evidence and returns a public_result headline with its supporting findings. For a private check, set privacy to private and public_receipt to false; public URLs otherwise default to public checks with signed receipts. Every successful response lists which checks ran, so an unresolved origin is reported as exactly that. [Follow the API integration guide](https://isgenai.com/guides/ai-detector-api)

### I am looking for an API to read InvokeAI settings from PNG files, does one exist?

Yes. Send the original PNG to isGenAI’s POST /v1/prompt endpoint with mode=saved_only to read InvokeAI metadata, and the same endpoint reads AUTOMATIC1111 and ComfyUI records. It returns the fields the file still carries, read exactly as saved; an export or screenshot that removed them gets a clean not-found response instead of a guess. The downloadable Node.js example handles saved results and missing-record errors for you. [Download the Node.js extraction example](https://isgenai.com/examples/extract-saved-prompt.mjs)

### Should I use a provenance API to check known copies of an image?

Yes. GET /v1/content/{content_id}/variants returns the known copies and variants inside the isGenAI corpus, a curated record rather than a whole-web reverse-image search. Public signed receipts and the published verification key let you verify a receipt’s integrity independently. Persistent cases also accept submitted creator or provider proof for validation. [Understand provenance and signature limits](https://isgenai.com/content-credentials)

## Related pages

- [Working API example](https://isgenai.com/guides/ai-detector-api)
- [OpenAPI spec](https://isgenai.com/openapi.json)
- [MCP server](https://isgenai.com/developers/mcp)
- [Public data API](https://isgenai.com/data)
- [Checker methodology](https://isgenai.com/checker-methodology)