Blue Crab

Blue Crab

The personal web crawling app for downloading and searching websites.

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System Requirements:

macOS 10.14



Blue Crab Screenshot


Blue Crab is a versatile app that you use to download the contents of a website to your Mac, in whole or in part. With Blue Crab you can:

• Conduct fast offline browsing and searching of a website.

• Create a snapshot of a website for historical archiving.

• Collect specific types of resources such as images or email addresses.

• Search current content more thoroughly than a search engine right on your Mac.

• Check a website for broken links, or generate a site map.

• Download groups of URL links at one time.


To get started with Blue Crab, check out the Blue Crab Tour. Read the full documentation for more information.

With Blue Crab you can download all the content including HTML, PDFs, graphics, video, file archives, etc., or use selective filtering to restrict downloads to specific kinds of files. For example, you can choose to save only the images Blue Crab finds, or just the PDFs. Blue Crab also supports "batch downloading" where you can collect a bunch of URLs, say by dragging them out of a browser window into Blue Crab, and then download them all at once. Use the Batch Download window for that.


Blue Crab Screenshot


Starting with a single webpage address Blue Crab begins traversing the site by following the links on the textual pages it finds, HTML, CSS, etc. Blue Crab does not stray off the domain of the starting URL; in other words it won't try to download the whole web! You can restrict Blue Crab to a subset of the given website by specifying strings that restrict which URLs are grabbed. There is also a convenient "stay in folder" option in every grabber window which restricts the crawl to URLs whose path must begin with the path of the starting URL. Use the Configuration Editor to modify the behavior of the crawling process.


Blue Crab has a special feature called the "Media Grabber" for easily downloading just the graphics, movies or PDFs on a website. When finding images, you can view a mini slide show as they are downloaded. You also have the option of "flattening" the download directory, i.e. putting all the downloaded images into one folder, or preserving the folder structure on the server, just as when downloading a whole website.


Once you download a collection of files you can search them with the built in text search window, which displays found files hierarchically, matching their location on the website. Blue Crab can search any file type supported by Spotlight, such as PDF or RTF, and provides convenient thumbnail previews. You can even view the index associated with each individual found file.


Blue Crab Screenshot


Finally, Blue Crab is gentle on the server. It processes only one URL at a time and may be configured to grab resources at delayed time intervals to further slow it down. This is important because it reduces stress on the server.