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Version: 3.4

HTTP crawler

This example demonstrates how to use HttpCrawler to crawl a list of URLs from an external file, load each URL using a plain HTTP request, and save HTML.

import { Dataset, HttpCrawler, log, LogLevel } from 'crawlee';

// Crawlers come with various utilities, e.g. for logging.
// Here we use debug level of logging to improve the debugging experience.
// This functionality is optional!

// Create an instance of the HttpCrawler class - a crawler
// that automatically loads the URLs and saves their HTML.
const crawler = new HttpCrawler({
// The crawler downloads and processes the web pages in parallel, with a concurrency
// automatically managed based on the available system memory and CPU (see AutoscaledPool class).
// Here we define some hard limits for the concurrency.
minConcurrency: 10,
maxConcurrency: 50,

// On error, retry each page at most once.
maxRequestRetries: 1,

// Increase the timeout for processing of each page.
requestHandlerTimeoutSecs: 30,

// Limit to 10 requests per one crawl
maxRequestsPerCrawl: 10,

// This function will be called for each URL to crawl.
// It accepts a single parameter, which is an object with options as:
// We use for demonstration only 2 of them:
// - request: an instance of the Request class with information such as the URL that is being crawled and HTTP method
// - body: the HTML code of the current page
async requestHandler({ request, body }) {
log.debug(`Processing ${request.url}...`);

// Store the results to the dataset. In local configuration,
// the data will be stored as JSON files in ./storage/datasets/default
await Dataset.pushData({
url: request.url,

// This function is called if the page processing failed more than maxRequestRetries + 1 times.
failedRequestHandler({ request }) {
log.debug(`Request ${request.url} failed twice.`);

// Run the crawler and wait for it to finish.

log.debug('Crawler finished.');