# FetchDelta Diff API

> FetchDelta Diff API is a paid API for AI agents from fetchdelta.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-15).

Compares the latest fetched content of a web page with its previous snapshot and returns structured changes (diffs).

## Facts

- Endpoint: GET https://fetchdelta.com/api/diff
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fetchdelta-com-4ba3edb5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vn13SBwLYYSeo3Tvpb1TE

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability fetchdelta-com-4ba3edb5
```

Example prompt: Can you check what has changed on https://example.com/pricing since the last time it was fetched and show me the structured diff of any content updates?

## When to prefer this

Use this endpoint when you need to detect what has changed on a specific web page between the current fetch and a prior snapshot. It is the right choice for monitoring pages for updates, verifying content changes, or alerting on modifications — especially when you already have a prior crawl stored and want a structured diff rather than raw content.

## Known failure modes

- URL is unreachable or returns a non-200 status — diff cannot be computed
- No previous snapshot exists for the URL — first-time fetch with nothing to compare against
- URL parameter missing or malformed — validation error returned
- Page content is unchanged — empty or null diff returned
- Rate limit or payment failure — 402 or 429 error

## How this service works

Compare a public page against its previous snapshot and return structured changes plus a 30-day daily-watch upgrade.

## Output

A structured object describing the differences between the current page content and the previously stored snapshot — including added, removed, or modified sections of the page.

## Example request

```json
{
 "input": {
  "type": "http",
  "method": "GET",
  "queryParams": {
   "url": "https://example.com"
  }
 }
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "format": "uri",
       "description": "Absolute URL of a public HTTP(S) page to fetch. Use docs, changelogs, release notes, pricing pages, policy pages, or other public pages. Private, localhost, credentialed, and non-HTTP(S) URLs are rejected."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "url": "https://example.com/",
  "preview": [
   {
    "text": "New paragraph",
    "type": "added"
   }
  ],
  "addedLines": 3,
  "hasChanges": true,
  "removedLines": 1,
  "baselineCreated": false,
  "monitoringUpgrade": {
   "price": "$0.50",
   "method": "GET",
   "maxUrls": 5,
   "product": "page-watch-30d",
   "currency": "USDC",
   "protocol": "x402",
   "checkoutUrl": "https://fetchdelta.com/api/page-watch-30d?url=https%3A%2F%2Fexample.com%2F",
   "description": "Create an account-free daily change watch for this page, valid for 30 days.",
   "durationDays": 30
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fetchdelta-com-4ba3edb5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fetchdelta.com](https://www.zero.xyz/host/fetchdelta.com/llms.txt)