What is a Seed URL in Web Crawling?

What Are Seed URLs?

A seed URL is the first address a web crawler visits when it begins a crawl job. It's the launchpad — the crawler loads the page at this URL, parses the HTML for outbound links, and adds every new URL it finds to a queue (commonly referred to as the URL frontier). From there, the process repeats recursively until the crawler has covered the scope you defined.

If the seed URL is your starting city on a road trip, the links on that page are the highways connecting you to every other destination.

Why Choosing the Right Seed URL Matters

Seed URL selection has a direct impact on three things: coverage, speed, and resource efficiency.

• Coverage — A seed URL with many outbound links (like a homepage or sitemap index) gives the crawler fast access to a large portion of a site. A deep, isolated URL might leave entire sections undiscovered.
• Speed — Starting from a well-connected page means the crawler reaches important content in fewer hops, reducing total crawl time.
• Resource efficiency — Poor seed choices lead to wasted requests on irrelevant pages, burning through your crawl budget before the crawler reaches the content you actually need.

Where Do Seed URLs Come From?

There are several common sources:

XML Sitemaps

Sitemaps list the pages a site owner considers important. Feeding sitemap URLs as seeds gives the crawler a curated, high-quality starting set — especially useful for large sites with thousands of pages.

Homepages

For most websites, the homepage links to the main navigation sections and top-level categories, making it a natural seed. It's the simplest approach and works well for broad, domain-wide crawls.

Hub and Category Pages

When you're crawling for a specific type of data — product listings, blog archives, directory pages — starting from the relevant hub page is more efficient than the homepage. The crawler reaches target content immediately without wasting cycles on unrelated sections.

Previous Crawl Results

Re-crawl workflows often use URLs from a prior run as seeds. This keeps indexes fresh and ensures previously discovered pages are revisited for updates.

Manual Submissions

Developers and site owners can submit URLs directly to search engines (via tools like Google Search Console) or pass them as parameters to a web crawling API.

Seed URL Strategies for Different Goals

Full-Site Archiving

Use the homepage plus the XML sitemap as seeds. This combination ensures you cover both the navigational structure and any orphan pages only listed in the sitemap.

Targeted Data Collection

Pick category or listing pages relevant to your data needs. If you're scraping product prices, start from the product catalog page — not the company's "About Us" section.

Multi-Domain Crawling

When crawling across many domains, diversify your seed set to avoid over-indexing a single site. One or two seeds per domain is usually enough to achieve broad coverage without redundancy.

How Many Seed URLs Should You Use?

There's a trade-off. A single seed URL keeps things simple but can become a bottleneck on large sites — the crawler has to discover everything through one chain of links. Multiple seeds enable parallel discovery and faster coverage.

That said, too many overlapping seeds waste effort. If five seed URLs all lead to the same set of pages, the crawler ends up de-duplicating rather than discovering. The sweet spot depends on the site's size and link structure, but a good rule of thumb: start with a small, diverse set and expand only if coverage gaps appear.

Seed URLs and Olostep

With Olostep's crawling API, you provide one or more seed URLs and the system handles the rest — link discovery, de-duplication, proxy rotation, and structured data delivery. You can also point the crawler at a sitemap URL to automatically expand the seed set for comprehensive coverage.