# Why is LCP slow? Find the LCP element and its delay

**Use case:** 

For pages that fail Largest Contentful Paint: which element is the LCP (CSS selector and text), and how its time splits into time to first byte, resource load delay, resource load duration and element render delay. Fixes that shorten LCP are listed first. The example pages fail LCP for real mobile visitors.

## Input

```json
{
  "urls": [
    "https://www.cnet.com",
    "https://wordpress.org",
    "https://www.walmart.com"
  ],
  "devices": "mobile",
  "trend": true
}
```

## Output

```json
{
  "url": {
    "label": "URL",
    "format": "string"
  },
  "mobile": {
    "label": "Mobile",
    "format": "object"
  }
}
```

## How it works

### 1. Sign up on Apify or log in

The PageSpeed Insights & Core Web Vitals Checker: Causes & Fixes Actor is ready to run with the inputs already set for "Why is LCP slow? Find the LCP element and its delay". [Sign up or log in](https://console.apify.com/create-task-from-example/OxWpLataecbXuiMqv) and you'll land in Apify Console with a copy of this exact task.

### 2. Start the "Why is LCP slow? Find the LCP element and its delay" task

The PageSpeed Insights & Core Web Vitals Checker: Causes & Fixes Actor will start running based on the input automatically. You can also change all the input fields, like page urls, devices, and more, to match your specific use case.

### 3. Receive the "Why is LCP slow? Find the LCP element and its delay" output

Monitor the progress in real time. You will be notified as soon as your dataset is complete and ready for review. Each result includes data such as URL and mobile.

### 4. Integrate into your workflow

The final output is delivered in JSON, CSV, or Excel format, ready to be plugged into your workflow. You can also [run the "Why is LCP slow? Find the LCP element and its delay" task via API](https://apify.com/crawlwise/pagespeed-core-web-vitals.md).

## About this Actor

This example demonstrates how to use [PageSpeed Insights & Core Web Vitals Checker: Causes & Fixes](https://apify.com/crawlwise/pagespeed-core-web-vitals.md) with a specific input configuration. Visit the [Actor detail page](https://apify.com/crawlwise/pagespeed-core-web-vitals.md) to learn more, explore other use cases, and run it yourself.


## How to integrate an Actor?

This Task's input is already configured above. Use it as-is rather than inventing a new one.

Do not guess an integration path. Every one of them is in the agent quickstart at https://apify.com/agents.md: the Apify MCP server, Agent Skills with the Apify CLI, the JavaScript and Python clients, the REST API, and the account-free path for an agent with no human to sign in. It also carries the rule on stating cost before the first paid run.

For full API examples (JavaScript, Python, CLI, MCP, OpenAPI), see this Task's Actor page: https://apify.com/crawlwise/pagespeed-core-web-vitals.md

Each client library has reference documentation the quickstart does not restate: [JavaScript/TypeScript](https://docs.apify.com/api/client/js/docs.md) (`npm install apify-client`) and [Python](https://docs.apify.com/api/client/python/docs.md) (`pip install apify-client`).