When you crawl for URLs using a pattern, FetchFox needs a set of URLs to start at. Those URLs can be set in one of two ways:
  • **Automatic: **You can let FetchFox determine the starting URLs for you.
  • Explicit: You can tell FetchFox which URLs to start crawling from.
Let’s look at both of these options.

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Automatically determine the starting URLs

By default, FetchFox will automatically determine the staring URLs for you. FetchFox include the following URLs in its starting URL set:
  • **The top level domain. **If you pass in https://example.com/category/*, then the URL https://example.com will be included in the starting URL set.
  • Path excluding wildcards. FetchFox will also guess URLs based on the pattern you pass in. It will do this by removing the wildcards and constructing URLs. For example, https://example.com/a/b/* will yield the guesses https://example.com/a/b and https://example.com/a .
  • Sitemap files. If the target domain has a sitemap file, FetchFox may include those URLs in the starting URL set.
  • **Known URLs from previous crawls. **If FetchFox has crawled a domain before, it will pull a sample of known URLs from the database and add those to the starting URL set.

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Explicitly setting the starting URLs

The start_urls parameter lets you explicitly set the starting URLs for a crawl. If you set the starting URLs in this way, FetchFox will use only those URLs as a starting point, and will not add URLs to the set you provide. Setting the starting URLs is helpful for crawling specific parts of large sites. It is especially useful in combination with the max_depth parameter, which limits the maximum depth of a crawl. You can use these two parameters to find links only from a specific set of pages. For example, suppose you are scraping commits on specific repos on GitHub. You can pass in the target repos in start_urls, and limit the depth to 0, as shown in the example below. 
curl -X POST https://api.fetchfox.ai/api/crawl \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $FETCHFOX_API_KEY" \
-d '{
    "pattern":"https://github.com/*/commit/*",
    "start_urls": [
      "https://github.com/bitcoin/bitcoin/commits/master/",
      "https://github.com/torvalds/linux/commits/master/"
    ],
    "max_depth": 0
}'
The call above will find commit URLs for the target repos, without wasting time on irrelevant parts of the site.