# Universal Price & Availability Change Monitor (`swholmes/universal-change-monitor`) Actor Monitor any web page or product URL for changes. Returns a structured diff and can POST alerts to a webhook. Scheduled, recurring, pay-per-event. - **URL**: https://apify.com/swholmes/universal-change-monitor.md - **Developed by:** [Scott Holmes](https://apify.com/swholmes) (community) - **Categories:** Automation, Developer tools, E-commerce - **Stats:** 1 total users, 0 monthly users, 0.0% runs succeeded, 0 bookmarks - **User rating**: No ratings yet ## Pricing from $1.00 / 1,000 url checkeds 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/docs.md): ```bash npm install apify-client ``` In Python projects, use official [Python client library](https://docs.apify.com/api/client/python/docs.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/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 ## Universal Price & Availability Change Monitor Watch any list of web pages for changes. On each run the Actor fetches every target, extracts a signal (raw content, a price, or a stock status), compares it to the snapshot saved from the previous run, and reports anything that changed. Optionally POSTs each change to a webhook so you can wire it into Slack, email, n8n, or your own app. Built to run on a schedule (for example hourly or daily). The first run stores a baseline; later runs produce diffs. ### Input | Field | Type | Notes | |---|---|---| | `targets` | array | Required. `[{ "url": "...", "selector": ".price", "label": "..." }]`. `selector` and `label` are optional. | | `mode` | string | `content` (any text change), `price` (first price-like value), or `availability` (in/out of stock). | | `webhookUrl` | string | Optional. Each change is POSTed here as JSON. | | `renderJs` | boolean | Turn on for client-side-rendered pages. Slower, uses a headless browser. | | `proxyConfiguration` | object | Apify Proxy config. Residential recommended for defended targets. | ### Output One dataset record per detected change: ```json { "label": "Widget product page", "url": "https://shop.example.com/widget", "selector": ".price", "mode": "price", "changed": true, "changeType": "price", "before": "$19.99", "after": "$17.49", "checkedAt": "2026-07-11T14:03:00.000Z" } ```` ### Monetization (pay-per-event) The code charges two events; define their prices in the Apify Console under Monetization: - `url-checked` — charged once per target per run (covers compute/proxy). - `change-detected` — charged only when an actual change is found (the value moment). This lets you price cheap polling with a premium on useful hits. ### How it works Snapshots are stored in a named Key-Value Store (`change-monitor-snapshots`), keyed on `url + selector`, so diffs survive across scheduled runs. Content mode compares normalized text (capped at 20k chars to keep runs cheap); price mode extracts the first currency-like token; availability mode looks for stock keywords. ### Notes / next steps - Add per-target `mode` if you want to mix price and content watches in one run. - Add a "changed lines" diff (currently reports before/after values) if subscribers want granular content diffs. - For heavily defended targets, enable `renderJs` and residential proxies. # Actor input Schema ## `targets` (type: `array`): One entry per page to watch. `url` is required. `selector` narrows monitoring to a CSS region (recommended for price/stock). `label` names the target in output. ## `mode` (type: `string`): content = any text change in the selected region. price = extract the first price-like number. availability = watch for in/out-of-stock keywords. ## `webhookUrl` (type: `string`): If set, a JSON payload is POSTed here for every detected change. ## `renderJs` (type: `boolean`): Enable for pages that build content client-side. Slower and more expensive (uses a headless browser). ## `proxyConfiguration` (type: `object`): Proxy configuration. Residential proxies are recommended for defended targets. ## Actor input object example ```json { "targets": [ { "url": "https://example.com", "selector": "", "label": "Example homepage" } ], "mode": "content", "renderJs": false, "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 '' with your token const client = new ApifyClient({ token: '', }); // Prepare Actor input const input = { "targets": [ { "url": "https://example.com", "selector": "", "label": "Example homepage" } ] }; // Run the Actor and wait for it to finish const run = await client.actor("swholmes/universal-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 '' with your token. client = ApifyClient("") # Prepare the Actor input run_input = { "targets": [{ "url": "https://example.com", "selector": "", "label": "Example homepage", }] } # Run the Actor and wait for it to finish run = client.actor("swholmes/universal-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 '{ "targets": [ { "url": "https://example.com", "selector": "", "label": "Example homepage" } ] }' | apify call swholmes/universal-change-monitor --silent --output-dataset ``` ## MCP server setup ```json { "mcpServers": { "apify": { "command": "npx", "args": [ "mcp-remote", "https://mcp.apify.com/?tools=swholmes/universal-change-monitor", "--header", "Authorization: Bearer " ] } } } ``` ## OpenAPI specification ```json { "openapi": "3.0.1", "info": { "title": "Universal Price & Availability Change Monitor", "description": "Monitor any web page or product URL for changes. Returns a structured diff and can POST alerts to a webhook. Scheduled, recurring, pay-per-event.", "version": "0.1", "x-build-id": "13EGV452QS39TRPdO" }, "servers": [ { "url": "https://api.apify.com/v2" } ], "paths": { "/acts/swholmes~universal-change-monitor/run-sync-get-dataset-items": { "post": { "operationId": "run-sync-get-dataset-items-swholmes-universal-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": { "$ref": "#/components/schemas/inputSchema" } } } }, "parameters": [ { "name": "token", "in": "query", "required": true, "schema": { "type": "string" }, "description": "Enter your Apify token here" } ], "responses": { "200": { "description": "OK" } } } }, "/acts/swholmes~universal-change-monitor/runs": { "post": { "operationId": "runs-sync-swholmes-universal-change-monitor", "x-openai-isConsequential": false, "summary": "Executes an Actor and returns information about the initiated run in response.", "tags": [ "Run Actor" ], "requestBody": { "required": true, "content": { "application/json": { "schema": { "$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": { "$ref": "#/components/schemas/runsResponseSchema" } } } } } } }, "/acts/swholmes~universal-change-monitor/run-sync": { "post": { "operationId": "run-sync-swholmes-universal-change-monitor", "x-openai-isConsequential": false, "summary": "Executes an Actor, waits for completion, and returns the OUTPUT from Key-value store in response.", "tags": [ "Run Actor" ], "requestBody": { "required": true, "content": { "application/json": { "schema": { "$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": [ "targets" ], "properties": { "targets": { "title": "Targets to monitor", "type": "array", "description": "One entry per page to watch. `url` is required. `selector` narrows monitoring to a CSS region (recommended for price/stock). `label` names the target in output." }, "mode": { "title": "Watch mode", "enum": [ "content", "price", "availability" ], "type": "string", "description": "content = any text change in the selected region. price = extract the first price-like number. availability = watch for in/out-of-stock keywords.", "default": "content" }, "webhookUrl": { "title": "Alert webhook URL (optional)", "type": "string", "description": "If set, a JSON payload is POSTed here for every detected change." }, "renderJs": { "title": "Render JavaScript", "type": "boolean", "description": "Enable for pages that build content client-side. Slower and more expensive (uses a headless browser).", "default": false }, "proxyConfiguration": { "title": "Proxy", "type": "object", "description": "Proxy configuration. Residential proxies are recommended for defended targets.", "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 } } } } } } } } } } ```