What Is Crawling
Crawl | Definition of Crawl by Merriam-Webster
\ ˈkrȯl
\
crawled; crawling; crawls
intransitive verb
1a: to move on one’s hands and knees
The baby crawled toward her mother.
b: to move slowly in a prone position without or as if without the use of limbs
The snake crawled into its hole. The soldiers crawled forward on their bellies.
2: to move or progress slowly or laboriously
traffic crawling along at 10 miles an hour
3: to advance by guile or servility
crawling into favor by toadying to his boss
4: to spread by extending stems or tendrils
a crawling vine
5a: to be alive or swarming with or as if with creeping things
a kitchen crawling with ants
b: to have the sensation of insects creeping over one
the story made her flesh crawl
6: to fail to stay evenly spread
—used of paint, varnish, or glaze
transitive verb
1: to move upon in or as if in a creeping manner
all the creatures that crawl the earth
2: to reprove harshly
they got no good right to crawl me for what I wrote— Marjorie K. Rawlings
1a: the act or action of crawling
b: slow or laborious progress
c
chiefly British: a going from one pub to another
2: a fast swimming stroke executed in a prone position with alternating overarm strokes and a flutter kick
3: lettering that moves vertically or horizontally across a television or motion-picture screen to give information (such as performer credits or news bulletins)
How Do Search Engine Crawlers Work? – DeepCrawl
Now that you’ve got a top level understanding about how search engines work, let’s delve deeper into the processes that search engine and web crawlers use to understand the web. Let’s start with the crawling process.
What is Search Engine Crawling?
Crawling is the process used by search engine web crawlers (bots or spiders) to visit and download a page and extract its links in order to discover additional pages.
Pages known to the search engine are crawled periodically to determine whether any changes have been made to the page’s content since the last time it was crawled. If a search engine detects changes to a page after crawling a page, it will update it’s index in response to these detected changes.
How Does Web Crawling Work?
Search engines use their own web crawlers to discover and access web pages.
All commercial search engine crawlers begin crawling a website by downloading its file, which contains rules about what pages search engines should or should not crawl on the website. The file may also contain information about sitemaps; this contains lists of URLs that the site wants a search engine crawler to crawl.
Search engine crawlers use a number of algorithms and rules to determine how frequently a page should be re-crawled and how many pages on a site should be indexed. For example, a page which changes a regular basis may be crawled more frequently than one that is rarely modified.
How Can Search Engine Crawlers be Identified?
The search engine bots crawling a website can be identified from the user agent string that they pass to the web server when requesting web pages.
Here are a few examples of user agent strings used by search engines:
Googlebot User Agent
Mozilla/5. 0 (compatible; Googlebot/2. 1; +)
Bingbot User Agent
Mozilla/5. 0 (compatible; bingbot/2. 0; +)
Baidu User Agent
Mozilla/5. 0 (compatible; Baiduspider/2. 0; +)
Yandex User Agent
Mozilla/5. 0 (compatible; YandexBot/3. 0; +)
Anyone can use the same user agent as those used by search engines. However, the IP address that made the request can also be used to confirm that it came from the search engine – a process called reverse DNS lookup.
Crawling images and other non-text files
Search engines will normally attempt to crawl and index every URL that they encounter.
However, if the URL is a non-text file type such as an image, video or audio file, search engines will typically not be able to read the content of the file other than the associated filename and metadata.
Although a search engine may only be able to extract a limited amount of information about non-text file types, they can still be indexed, rank in search results and receive traffic.
You can find a full list of file types that can be indexed by Google available here.
Crawling and Extracting Links From Pages
Crawlers discover new pages by re-crawling existing pages they already know about, then extracting the links to other pages to find new URLs. These new URLs are added to the crawl queue so that they can be downloaded at a later date.
Through this process of following links, search engines are able to discover every publicly-available webpage on the internet which is linked from at least one other page.
Sitemaps
Another way that search engines can discover new pages is by crawling sitemaps.
Sitemaps contain sets of URLs, and can be created by a website to provide search engines with a list of pages to be crawled. These can help search engines find content hidden deep within a website and can provide webmasters with the ability to better control and understand the areas of site indexing and frequency.
Page submissions
Alternatively, individual page submissions can often be made directly to search engines via their respective interfaces. This manual method of page discovery can be used when new content is published on site, or if changes have taken place and you want to minimise the time that it takes for search engines to see the changed content.
Google states that for large URL volumes you should use XML sitemaps, but sometimes the manual submission method is convenient when submitting a handful of pages. It is also important to note that Google limits webmasters to 10 URL submissions per day.
Additionally, Google says that the response time for indexing is the same for sitemaps as individual submissions.
Next: Search Engine Indexing
Author
Sam Marsden
Sam Marsden is Deepcrawl’s Former SEO & Content Manager. Sam speaks regularly at marketing conferences, like SMX and BrightonSEO, and is a contributor to industry publications such as Search Engine Journal and State of Digital.
How Google’s Site Crawlers Index Your Site – Google Search
Чтобы пользователи могли быстро найти нужные сведения, наши роботы собирают информацию на сотнях миллиардов страниц и упорядочивают ее в поисковом индексе.
Основы Google Поиска
При очередном сканировании наряду со списком веб-адресов, полученных во время предыдущего сканирования, используются файлы Sitemap, которые предоставляются владельцами сайтов. По мере посещения сайтов робот переходит по указанным на них ссылкам на другие страницы. Особое внимание он уделяет новым и измененным сайтам, а также неработающим ссылкам. Он самостоятельно определяет, какие сайты сканировать, как часто это нужно делать и какое количество страниц следует выбрать на каждом из них.
При помощи Search Console владельцы сайтов могут указывать, как именно следует сканировать их ресурсы, в частности предоставлять подробные инструкции по обработке страниц, запрашивать их повторное сканирование, а также запрещать сканирование, используя файл Google не увеличивает частоту сканирования отдельных ресурсов за плату. Чтобы результаты поиска были максимально полезными для пользователей, все владельцы сайтов получают одни и те же инструменты.
Поиск информации с помощью сканирования
Интернет похож на библиотеку, которая содержит миллиарды изданий и постоянно пополняется, но не располагает централизованной системой учета книг. Чтобы находить общедоступные страницы, мы используем специальное программное обеспечение, называемое поисковыми роботами. Роботы анализируют страницы и переходят по ссылкам на них – как обычные пользователи. После этого они отправляют сведения о ресурсах на серверы Google.
Систематизация информации с помощью индексирования
Во время сканирования наши системы обрабатывают материалы страниц так же, как это делают браузеры, и регистрируют данные по ключевым словам и новизне контента, а затем создают на их основе поисковый индекс.
Индекс Google Поиска содержит сотни миллиардов страниц. Его объем значительно превышает 100 миллионов гигабайт. Он похож на указатель в конце книги, в котором есть отдельная запись для каждого слова на всех проиндексированных страницах. Во время индексирования данные о странице добавляются в записи по всем словам, которые на ней есть.
Построение Сети Знаний — более современный способ определить интересы пользователей по сравнению с сопоставлением ключевых слов. Для этого мы упорядочиваем не только данные по страницам, но и другие типы информации. В настоящее время Google Поиск позволяет найти нужный фрагмент текста в миллионах книг из крупнейших библиотек, узнать расписание общественного транспорта, а также изучить данные общедоступных источников, таких как сайт Всемирного банка.
Frequently Asked Questions about what is crawling
What is crawling explain?
1 : to move slowly with the body close to the ground : move on hands and knees. 2 : to go very slowly or carefully Traffic was crawling along. 3 : to be covered with or have the feeling of being covered with creeping things The food was crawling with flies.
What is crawling in search engine?
Crawling is the process used by search engine web crawlers (bots or spiders) to visit and download a page and extract its links in order to discover additional pages. … If a search engine detects changes to a page after crawling a page, it will update it’s index in response to these detected changes.
How is crawling done?
The crawling process begins with a list of web addresses from past crawls and sitemaps provided by website owners. As our crawlers visit these websites, they use links on those sites to discover other pages. The software pays special attention to new sites, changes to existing sites and dead links.