What does crawler mean?
A crawler is an agent or machine that moves by creeping along a surface, and the word has three well-established modern senses. Most prominently in contemporary life, a web crawler is an automated program that traverses the internet, following links from page to page in order to index content for search engines; without such crawlers, services like Google could not function. In heavy engineering, a crawler is a vehicle mounted on continuous metal or rubber tracks instead of wheels, giving it the grip and low ground pressure needed for mud, snow, and rough terrain — crawler tractors and crawler cranes are staples of construction and agriculture. Finally, in everyday language a crawler is simply a creature or person moving on hands and knees, most familiarly a baby at the crawling stage. The noun derives from the verb crawl, of Germanic origin, which has carried the sense of slow, low-to-the-ground movement since medieval times. The word spans registers, appearing both in casual speech and in precise technical vocabulary.
A program that automatically browses the internet to index web pages for search engines.
"The site blocked the crawler because it was requesting thousands of pages per minute."
Often used attributively as "web crawler"; also called a spider or robot in technical literature.
A vehicle, typically a tractor or crane, that travels on continuous tracks rather than wheels.
"A crawler crane was brought in to lift the bridge girders across the soft riverbank."
Standard terminology in construction, agriculture, and mining industries.
A person or animal that moves on hands and knees.
"The crawler pulled herself under the fence and into the neighbour's garden."
Regular plural formation. Used naturally when referring to multiple web-indexing programs, tracked vehicles, or babies moving on hands and knees.
"Search engines deploy many crawlers simultaneously to keep their indexes current."
The first web crawler, World Wide Web Wanderer, was launched in 1993 — and today crawlers account for a huge share of all internet traffic, quietly reading pages no human ever will.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of crawler
Crawler is formed from the English verb crawl plus the agentive suffix -er, following a productive Germanic pattern for naming things that perform an action. Crawl itself comes from Middle English crullen or crawl, probably of North Germanic origin and related to Old Norse krafla, meaning to claw or scrape along the ground. The sense of a tracked vehicle arose in the early twentieth century with caterpillar-track tractors, and the computing sense emerged in the 1990s as web-search technology developed. Cognates include the Scandinavian verbs krafla (Old Norse) and its modern descendants, while related English words such as creep share the semantic field of low, slow movement.
Related word forms
How crawler is actually used
"Crawler" is common in technical and engineering contexts, where "web crawler" and "crawler tractor" are standard industry terms. Applied to people it can sound slightly undignified, so writers usually prefer "baby" or specify the context. The plural is straightforward.
Easily confused with crawler
Crawl is the verb describing slow movement on hands and knees or the swimming stroke; a crawler is the noun for the agent or machine that does the crawling.
A scrawler writes in a hasty, untidy hand; a crawler moves slowly on all fours or is a web-indexing program — the words share only superficial sound similarity.