# Website Change Monitor (`foo121/website-change-monitor`) Actor

Monitor any list of URLs for true content changes — CSS-selector targeting, keyword watches, noise-filtered diffing and webhook-on-change. Built for scheduled runs. Pay per result.

- **URL**: https://apify.com/foo121/website-change-monitor.md
- **Developed by:** [ziv shay](https://apify.com/foo121) (community)
- **Categories:** Developer tools, Automation
- **Stats:** 2 total users, 1 monthly users, 100.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

$5.00 / 1,000 result items

This Actor is paid per event. You are not charged for the Apify platform usage, but only a fixed price for specific events.

Learn more: https://docs.apify.com/platform/actors/running/actors-in-store#pay-per-event

## What's an Apify Actor?

Actors are a software tools running on the Apify platform, for all kinds of web data extraction and automation use cases.
In Batch mode, an Actor accepts a well-defined JSON input, performs an action which can take anything from a few seconds to a few hours,
and optionally produces a well-defined JSON output, datasets with results, or files in key-value store.
In Standby mode, an Actor provides a web server which can be used as a website, API, or an MCP server.
Actors are written with capital "A".

## How to integrate an Actor?

If asked about integration, you help developers integrate Actors into their projects.
You adapt to their stack and deliver integrations that are safe, well-documented, and production-ready.
The best way to integrate Actors is as follows.

In JavaScript/TypeScript projects, use official [JavaScript/TypeScript client](https://docs.apify.com/api/client/js.md):

```bash
npm install apify-client
```

In Python projects, use official [Python client library](https://docs.apify.com/api/client/python.md):

```bash
pip install apify-client
```

In shell scripts, use [Apify CLI](https://docs.apify.com/cli/docs.md):

````bash
# MacOS / Linux
curl -fsSL https://apify.com/install-cli.sh | bash
# Windows
irm https://apify.com/install-cli.ps1 | iex
```bash

In AI frameworks, you might use the [Apify MCP server](https://docs.apify.com/platform/integrations/mcp.md).

If your project is in a different language, use the [REST API](https://docs.apify.com/api/v2.md).

For usage examples, see the [API](#api) section below.

For more details, see Apify documentation as [Markdown index](https://docs.apify.com/llms.txt) and [Markdown full-text](https://docs.apify.com/llms-full.txt).


# README

## Website Change Monitor

**Monitor any list of URLs for *true* content changes — and fire a webhook only when something real changes.** CSS-selector targeting, keyword watches, noise-filtered diffing, and clean machine-consumable output. Built for scheduled runs. Pay per result.

Most "website change detection" actors diff raw HTML, so they fire on every page load — cache busters, session tokens, ad slots and timestamps all look like "changes." This actor normalizes the page first (strips scripts/styles/comments, volatile attributes, hashes, session ids, cache-buster query params, whitespace reflow) and compares against the **last scheduled run**, so you get signal, not noise.

### What it does

- Fetches each URL, extracts the watched region (whole page or a **CSS selector**).
- Normalizes content and compares it to the previous run's snapshot (stored in a persistent named Key-Value store — it survives between scheduled runs).
- Emits a structured **change-event** per URL that actually changed: added/removed lines, counts, a unified-diff preview, a 0–1 change ratio, and keyword appeared/disappeared signals.
- A `minChangeRatio` threshold suppresses trivial edits.

### Why it's different

- **True-change detection, not raw-HTML diffing.** Volatile noise is stripped before comparison, so you don't get paged on a cache-buster.
- **State persists across scheduled runs.** It compares against your *last* run, not within one run — the only way change detection actually works on a schedule.
- **Clean output.** `addedLines` / `removedLines` / `changeRatio` / `keywordsAppeared` are webhook-ready — your consumer acts on the fields, no HTML parsing.

### Input

| Field | Type | Description |
|---|---|---|
| `startUrls` | array | URLs to watch. Strings, or objects with per-URL `url` + `selector` + `keywords`. |
| `selector` | string | Global CSS selector applied to URLs that don't set their own. Blank = whole `<body>`. |
| `keywords` | array | Words to watch; run reports present + appeared/disappeared (e.g. `In stock`, `Sold out`). |
| `mode` | string | `text` (default, ignores markup churn) or `html`. |
| `minChangeRatio` | number | 0–1. Only flag a change when ≥ this fraction of lines changed. |
| `emitUnchanged` | boolean | Also output unchanged URLs (default off → webhook fires only on real changes). |
| `storeArchive` | boolean | Store previous content for line-level diffs (default on). |
| `proxyConfiguration` | object | Apify proxy (recommended). |

#### Example input

```json
{
  "startUrls": [
    "https://news.ycombinator.com",
    { "url": "https://shop.example.com/item", "selector": ".price", "keywords": ["In stock", "Sold out"] }
  ],
  "minChangeRatio": 0.02
}
````

### Output

One change-event per changed/first-seen/errored URL:

```json
{
  "url": "https://shop.example.com/item",
  "changed": true,
  "changeType": "changed",
  "fingerprint": "a1b2c3d4e5f60718",
  "previousFingerprint": "9988776655443322",
  "addedLines": ["$24.99", "In stock"],
  "removedLines": ["$29.99", "Sold out"],
  "addedCount": 2,
  "removedCount": 2,
  "changeRatio": 0.5,
  "keywordsAppeared": ["In stock"],
  "keywordsDisappeared": ["Sold out"],
  "preview": "- $29.99\n- Sold out\n+ $24.99\n+ In stock",
  "checkedAt": "2026-06-21T13:40:00.000Z",
  "previousCheckedAt": "2026-06-21T12:40:00.000Z"
}
```

`changeType` is one of: `first_seen`, `unchanged`, `below_threshold`, `changed`, `error`.

### Schedule + webhook

1. **Schedule** the actor (e.g. hourly/daily) — the named state store remembers the last snapshot between runs.
2. Add an Apify **webhook** on *run succeeded* and, in your endpoint, act on rows where `changed: true`. Or use the dataset's `changed`/`changeType` fields to filter.

### Pricing

Pay per result — you're charged per change-event row returned. Default output mode only returns rows that changed (or were first-seen / errored), so steady-state monitoring of stable pages is cheap.

***

*Built by MoneyMachine. Public data only; respect each site's terms and robots.*

# Actor input Schema

## `startUrls` (type: `array`):

List of pages to watch for changes. Paste plain URLs, or objects to set a per-URL CSS `selector` and `keywords`, e.g. { "url": "https://shop.com/item", "selector": ".price", "keywords": \["In stock", "Sold out"] }. Each URL produces at most one change-event row per run.

## `selector` (type: `string`):

Optional CSS selector applied to every URL that doesn't set its own. Narrows watching to one region (e.g. ".price", "main", "#content") so changes elsewhere on the page are ignored. Leave blank to watch the whole <body>.

## `keywords` (type: `array`):

Optional keywords. Each run reports which are present, plus which appeared/disappeared since last run (e.g. watch "In stock" / "Sold out" / "Apply now").

## `mode` (type: `string`):

Compare visible text (recommended — ignores markup churn) or raw HTML of the selected region.

## `minChangeRatio` (type: `number`):

Suppress trivial edits: a change is only flagged when the fraction of changed lines is at least this value. 0 = report any change. 0.05 = ignore <5% edits.

## `emitUnchanged` (type: `boolean`):

If on, every checked URL produces a row (changed or not). Default only outputs rows that changed, were first-seen, or errored — so a webhook fires only on real changes.

## `storeArchive` (type: `boolean`):

Store the previous normalized content so the next run can produce added/removed line diffs. Turn off to compare by fingerprint only (lighter, no diff preview).

## `requestTimeoutSecs` (type: `integer`):

Abort a single fetch after this many seconds.

## `maxConcurrency` (type: `integer`):

How many URLs to check in parallel.

## `proxyConfiguration` (type: `object`):

Proxy for outbound requests. Apify proxy recommended to avoid rate limits across scheduled runs.

## Actor input object example

```json
{
  "startUrls": [
    "https://news.ycombinator.com",
    {
      "url": "https://www.iana.org/domains/reserved",
      "selector": "#main_right"
    }
  ],
  "selector": "",
  "keywords": [],
  "mode": "text",
  "minChangeRatio": 0,
  "emitUnchanged": false,
  "storeArchive": true,
  "requestTimeoutSecs": 30,
  "maxConcurrency": 10,
  "proxyConfiguration": {
    "useApifyProxy": true
  }
}
```

# API

You can run this Actor programmatically using our API. Below are code examples in JavaScript, Python, and CLI, as well as the OpenAPI specification and MCP server setup.

## JavaScript example

```javascript
import { ApifyClient } from 'apify-client';

// Initialize the ApifyClient with your Apify API token
// Replace the '<YOUR_API_TOKEN>' with your token
const client = new ApifyClient({
    token: '<YOUR_API_TOKEN>',
});

// Prepare Actor input
const input = {
    "startUrls": [
        "https://news.ycombinator.com",
        {
            "url": "https://www.iana.org/domains/reserved",
            "selector": "#main_right"
        }
    ]
};

// Run the Actor and wait for it to finish
const run = await client.actor("foo121/website-change-monitor").call(input);

// Fetch and print Actor results from the run's dataset (if any)
console.log('Results from dataset');
console.log(`💾 Check your data here: https://console.apify.com/storage/datasets/${run.defaultDatasetId}`);
const { items } = await client.dataset(run.defaultDatasetId).listItems();
items.forEach((item) => {
    console.dir(item);
});

// 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/js/docs

```

## Python example

```python
from apify_client import ApifyClient

# Initialize the ApifyClient with your Apify API token
# Replace '<YOUR_API_TOKEN>' with your token.
client = ApifyClient("<YOUR_API_TOKEN>")

# Prepare the Actor input
run_input = { "startUrls": [
        "https://news.ycombinator.com",
        {
            "url": "https://www.iana.org/domains/reserved",
            "selector": "#main_right",
        },
    ] }

# Run the Actor and wait for it to finish
run = client.actor("foo121/website-change-monitor").call(run_input=run_input)

# Fetch and print Actor results from the run's dataset (if there are any)
print("💾 Check your data here: https://console.apify.com/storage/datasets/" + run["defaultDatasetId"])
for item in client.dataset(run["defaultDatasetId"]).iterate_items():
    print(item)

# 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/python/docs/quick-start

```

## CLI example

```bash
echo '{
  "startUrls": [
    "https://news.ycombinator.com",
    {
      "url": "https://www.iana.org/domains/reserved",
      "selector": "#main_right"
    }
  ]
}' |
apify call foo121/website-change-monitor --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "command": "npx",
            "args": [
                "mcp-remote",
                "https://mcp.apify.com/?tools=foo121/website-change-monitor",
                "--header",
                "Authorization: Bearer <YOUR_API_TOKEN>"
            ]
        }
    }
}

```

## OpenAPI specification

```json
{
    "openapi": "3.0.1",
    "info": {
        "title": "Website Change Monitor",
        "description": "Monitor any list of URLs for true content changes — CSS-selector targeting, keyword watches, noise-filtered diffing and webhook-on-change. Built for scheduled runs. Pay per result.",
        "version": "1.0",
        "x-build-id": "89DLO7UlK1fWOxGMc"
    },
    "servers": [
        {
            "url": "https://api.apify.com/v2"
        }
    ],
    "paths": {
        "/acts/foo121~website-change-monitor/run-sync-get-dataset-items": {
            "post": {
                "operationId": "run-sync-get-dataset-items-foo121-website-change-monitor",
                "x-openai-isConsequential": false,
                "summary": "Executes an Actor, waits for its completion, and returns Actor's dataset items in response.",
                "tags": [
                    "Run Actor"
                ],
                "requestBody": {
                    "required": true,
                    "content": {
                        "application/json": {
                            "schema": {
                                "$ref": "#/components/schemas/inputSchema"
                            }
                        }
                    }
                },
                "parameters": [
                    {
                        "name": "token",
                        "in": "query",
                        "required": true,
                        "schema": {
                            "type": "string"
                        },
                        "description": "Enter your Apify token here"
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK"
                    }
                }
            }
        },
        "/acts/foo121~website-change-monitor/runs": {
            "post": {
                "operationId": "runs-sync-foo121-website-change-monitor",
                "x-openai-isConsequential": false,
                "summary": "Executes an Actor and returns information about the initiated run in response.",
                "tags": [
                    "Run Actor"
                ],
                "requestBody": {
                    "required": true,
                    "content": {
                        "application/json": {
                            "schema": {
                                "$ref": "#/components/schemas/inputSchema"
                            }
                        }
                    }
                },
                "parameters": [
                    {
                        "name": "token",
                        "in": "query",
                        "required": true,
                        "schema": {
                            "type": "string"
                        },
                        "description": "Enter your Apify token here"
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK",
                        "content": {
                            "application/json": {
                                "schema": {
                                    "$ref": "#/components/schemas/runsResponseSchema"
                                }
                            }
                        }
                    }
                }
            }
        },
        "/acts/foo121~website-change-monitor/run-sync": {
            "post": {
                "operationId": "run-sync-foo121-website-change-monitor",
                "x-openai-isConsequential": false,
                "summary": "Executes an Actor, waits for completion, and returns the OUTPUT from Key-value store in response.",
                "tags": [
                    "Run Actor"
                ],
                "requestBody": {
                    "required": true,
                    "content": {
                        "application/json": {
                            "schema": {
                                "$ref": "#/components/schemas/inputSchema"
                            }
                        }
                    }
                },
                "parameters": [
                    {
                        "name": "token",
                        "in": "query",
                        "required": true,
                        "schema": {
                            "type": "string"
                        },
                        "description": "Enter your Apify token here"
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK"
                    }
                }
            }
        }
    },
    "components": {
        "schemas": {
            "inputSchema": {
                "type": "object",
                "required": [
                    "startUrls"
                ],
                "properties": {
                    "startUrls": {
                        "title": "URLs to monitor",
                        "type": "array",
                        "description": "List of pages to watch for changes. Paste plain URLs, or objects to set a per-URL CSS `selector` and `keywords`, e.g. { \"url\": \"https://shop.com/item\", \"selector\": \".price\", \"keywords\": [\"In stock\", \"Sold out\"] }. Each URL produces at most one change-event row per run."
                    },
                    "selector": {
                        "title": "CSS selector (global)",
                        "type": "string",
                        "description": "Optional CSS selector applied to every URL that doesn't set its own. Narrows watching to one region (e.g. \".price\", \"main\", \"#content\") so changes elsewhere on the page are ignored. Leave blank to watch the whole <body>.",
                        "default": ""
                    },
                    "keywords": {
                        "title": "Keywords to watch (global)",
                        "type": "array",
                        "description": "Optional keywords. Each run reports which are present, plus which appeared/disappeared since last run (e.g. watch \"In stock\" / \"Sold out\" / \"Apply now\").",
                        "default": [],
                        "items": {
                            "type": "string"
                        }
                    },
                    "mode": {
                        "title": "Compare mode",
                        "enum": [
                            "text",
                            "html"
                        ],
                        "type": "string",
                        "description": "Compare visible text (recommended — ignores markup churn) or raw HTML of the selected region.",
                        "default": "text"
                    },
                    "minChangeRatio": {
                        "title": "Minimum change ratio (0-1)",
                        "minimum": 0,
                        "maximum": 1,
                        "type": "number",
                        "description": "Suppress trivial edits: a change is only flagged when the fraction of changed lines is at least this value. 0 = report any change. 0.05 = ignore <5% edits.",
                        "default": 0
                    },
                    "emitUnchanged": {
                        "title": "Also output unchanged URLs",
                        "type": "boolean",
                        "description": "If on, every checked URL produces a row (changed or not). Default only outputs rows that changed, were first-seen, or errored — so a webhook fires only on real changes.",
                        "default": false
                    },
                    "storeArchive": {
                        "title": "Archive content for line-level diffs",
                        "type": "boolean",
                        "description": "Store the previous normalized content so the next run can produce added/removed line diffs. Turn off to compare by fingerprint only (lighter, no diff preview).",
                        "default": true
                    },
                    "requestTimeoutSecs": {
                        "title": "Per-request timeout (seconds)",
                        "minimum": 5,
                        "maximum": 120,
                        "type": "integer",
                        "description": "Abort a single fetch after this many seconds.",
                        "default": 30
                    },
                    "maxConcurrency": {
                        "title": "Max concurrency",
                        "minimum": 1,
                        "maximum": 100,
                        "type": "integer",
                        "description": "How many URLs to check in parallel.",
                        "default": 10
                    },
                    "proxyConfiguration": {
                        "title": "Proxy configuration",
                        "type": "object",
                        "description": "Proxy for outbound requests. Apify proxy recommended to avoid rate limits across scheduled runs.",
                        "default": {
                            "useApifyProxy": true
                        }
                    }
                }
            },
            "runsResponseSchema": {
                "type": "object",
                "properties": {
                    "data": {
                        "type": "object",
                        "properties": {
                            "id": {
                                "type": "string"
                            },
                            "actId": {
                                "type": "string"
                            },
                            "userId": {
                                "type": "string"
                            },
                            "startedAt": {
                                "type": "string",
                                "format": "date-time",
                                "example": "2025-01-08T00:00:00.000Z"
                            },
                            "finishedAt": {
                                "type": "string",
                                "format": "date-time",
                                "example": "2025-01-08T00:00:00.000Z"
                            },
                            "status": {
                                "type": "string",
                                "example": "READY"
                            },
                            "meta": {
                                "type": "object",
                                "properties": {
                                    "origin": {
                                        "type": "string",
                                        "example": "API"
                                    },
                                    "userAgent": {
                                        "type": "string"
                                    }
                                }
                            },
                            "stats": {
                                "type": "object",
                                "properties": {
                                    "inputBodyLen": {
                                        "type": "integer",
                                        "example": 2000
                                    },
                                    "rebootCount": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "restartCount": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "resurrectCount": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "computeUnits": {
                                        "type": "integer",
                                        "example": 0
                                    }
                                }
                            },
                            "options": {
                                "type": "object",
                                "properties": {
                                    "build": {
                                        "type": "string",
                                        "example": "latest"
                                    },
                                    "timeoutSecs": {
                                        "type": "integer",
                                        "example": 300
                                    },
                                    "memoryMbytes": {
                                        "type": "integer",
                                        "example": 1024
                                    },
                                    "diskMbytes": {
                                        "type": "integer",
                                        "example": 2048
                                    }
                                }
                            },
                            "buildId": {
                                "type": "string"
                            },
                            "defaultKeyValueStoreId": {
                                "type": "string"
                            },
                            "defaultDatasetId": {
                                "type": "string"
                            },
                            "defaultRequestQueueId": {
                                "type": "string"
                            },
                            "buildNumber": {
                                "type": "string",
                                "example": "1.0.0"
                            },
                            "containerUrl": {
                                "type": "string"
                            },
                            "usage": {
                                "type": "object",
                                "properties": {
                                    "ACTOR_COMPUTE_UNITS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_WRITES": {
                                        "type": "integer",
                                        "example": 1
                                    },
                                    "KEY_VALUE_STORE_LISTS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_INTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_EXTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_RESIDENTIAL_TRANSFER_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_SERPS": {
                                        "type": "integer",
                                        "example": 0
                                    }
                                }
                            },
                            "usageTotalUsd": {
                                "type": "number",
                                "example": 0.00005
                            },
                            "usageUsd": {
                                "type": "object",
                                "properties": {
                                    "ACTOR_COMPUTE_UNITS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_WRITES": {
                                        "type": "number",
                                        "example": 0.00005
                                    },
                                    "KEY_VALUE_STORE_LISTS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_INTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_EXTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_RESIDENTIAL_TRANSFER_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_SERPS": {
                                        "type": "integer",
                                        "example": 0
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}
```