# Website Change Comparison API

> Website Change Comparison API is a paid API for AI agents from x402-safe-upgrade-api.onrender.com, paid per call via x402, $0.02/call, status down (last checked 2026-10-12).

Compares two snapshots of a webpage to identify added and removed content between versions.

## Facts

- Endpoint: POST https://x402-safe-upgrade-api.onrender.com/v1/website-change-comparison?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: down
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/website-change-comparison-api-8ed85f33
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_pqyFcgpE-Y3adq9eChfoF

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 website-change-comparison-api-8ed85f33 -d '<json body>'
```

Example prompt: Compare these two snapshots of https://npmjs.com/package/lodash and tell me what content was added or removed — here's the previous snapshot and the current one I just fetched.

## When to prefer this

Use this endpoint when you need to programmatically compare two text snapshots of a webpage and extract a structured list of what was added or removed — particularly useful for coding agents evaluating npm package upgrade safety by detecting changelog or documentation changes. Prefer this over generic diff tools when you need a clean JSON result distinguishing additions from removals in a web-content context.

## Known failure modes

- Snapshots too large — each is capped at 200,000 characters; exceeding this causes rejection
- Invalid or unreachable websiteUrl — malformed URI format returns an error
- Both snapshots identical — returns empty added/removed arrays with no error
- Malformed snapshot content (binary or non-text) may produce unexpected diff results
- Missing required fields in request body returns a validation error

## How this service works

Evidence-backed npm package upgrade decisions for coding agents.

## Output

A JSON object with a 'change' field containing two arrays: 'added' (content present in the current snapshot but not the previous) and 'removed' (content present in the previous snapshot but not the current), enabling precise diffing of webpage content.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "websiteUrl": {
   "type": "string",
   "format": "uri"
  },
  "currentSnapshot": {
   "type": "string",
   "maxLength": 200000,
   "description": "Content supplied by the caller only; it is processed in memory and not retained."
  },
  "previousSnapshot": {
   "type": "string",
   "maxLength": 200000,
   "description": "Content supplied by the caller only; it is processed in memory and not retained."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "change": {
   "added": [],
   "removed": []
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/website-change-comparison-api-8ed85f33/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-safe-upgrade-api.onrender.com](https://www.zero.xyz/host/x402-safe-upgrade-api.onrender.com/llms.txt)