What is the difference between web-crawling and web-scraping?

Search Engine Problem Overview

Is there a difference between Crawling and Web-scraping?

If there's a difference, what's the best method to use in order to collect some web data to supply a database for later use in a customised search engine?

Search Engine Solutions

Solution 1 - Search Engine

Crawling would be essentially what Google, Yahoo, MSN, etc. do, looking for ANY information. Scraping is generally targeted at certain websites, for specfic data, e.g. for price comparison, so are coded quite differently.

Usually a scraper will be bespoke to the websites it is supposed to be scraping, and would be doing things a (good) crawler wouldn't do, i.e.:

Have no regard for robots.txt
Identify itself as a browser
Submit forms with data
Execute Javascript (if required to act like a user)

Solution 2 - Search Engine

Yes, they are different. In practice, you may need to use both.

(I have to jump in because, so far, the other answers don't get to the essence of it. They use examples but don't make the distinctions clear. Granted, they are from 2010!)

Web scraping, to use a minimal definition, is the process of processing a web document and extracting information out of it. You can do web scraping without doing web crawling.

Web crawling, to use a minimal definition, is the process of iteratively finding and fetching web links starting from a list of seed URL's. Strictly speaking, to do web crawling, you have to do some degree of web scraping (to extract the URL's.)

To clear up some concepts mentioned in the other answers:

robots.txt is intended to apply to any automated process that accesses a web page. So it applies to both crawlers and scrapers.
'Proper' crawlers and scrapers, both, should identify themselves accurately.

Some references:

Solution 3 - Search Engine

AFAIK Web Crawling is what Google does - it goes around a website looking at links and building a database of the layout of that site and sites it links to

Web Scraping would be the progamatic analysis of a web page to load some data off of it, EG loading up BBC weather and ripping (scraping) the weather forcast off of it and placing it elsewhere or using it in another program.

Solution 4 - Search Engine

There's a fundamental difference between these two. For those looking to dig deeper, I suggest you read this - Web scraper, Web Crawler

This post goes into detail. A good summary is in this chart from the article:

Solution 5 - Search Engine

There's definitely a difference between these two. One refers to visiting a site, the other to extracting.

Solution 6 - Search Engine

We crawl sites to have broad perspective how the site is structured, what are connections between pages, to estimate how much time we need to visit all pages we are interested in. Scraping is often harder to implement, but it’s an essence of data extraction. Let’s think of scraping as of covering website with sheet of paper with some rectangles cut out. We can now see only things we need, completely ignoring parts of website that are common for all pages (like navigation, footer, ads), or extraneous informations as comments or breadcrumbs. More about differences between crawling and scrapping you find here: https://tarantoola.io/web-scraping-vs-web-crawling/

Content Type	Original Author	Original Content on Stackoverflow
Question	wassimans	View Question on Stackoverflow
Solution 1 - Search Engine	Ben	View Answer on Stackoverflow
Solution 2 - Search Engine	David J.	View Answer on Stackoverflow
Solution 3 - Search Engine	Chris Harden	View Answer on Stackoverflow
Solution 4 - Search Engine	Mohit Sharma	View Answer on Stackoverflow
Solution 5 - Search Engine	Annie	View Answer on Stackoverflow
Solution 6 - Search Engine	shirk3y	View Answer on Stackoverflow