Blue Crab
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Abstract
Blue Crab is a versatile program that you use to copy the contents of a web site to your computer, in whole or in part.
- Conduct fast offline browsing and searching without an internet connection.
- Create a snapshot of a web site 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 own computer.
- Check a site for broken links, or generate an HTML site map
- Perform batch downloads of URL's
- Create full page images of URL's (JPEG, BMP, TIFF, PNG, PSD, etc.)
With Blue Crab you can download all the content including HTML, PDF, 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 JPEG images Blue Crab finds, or just the PDF's. Blue Crab also supports "batch downloading" where you can collect a bunch of URLs (say by dragging them out of a browser window) then downloading them all at once:
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Starting with a single URL 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 download the whole web! Moreover, you can restrict Blue Crab to a subset of the given website by specifying strings that must match parts of the URL. 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 same path of the starting URL. Use the Configuration editor to modify the behavior of a grab:
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Blue Crab has a special feature called the "Media Grabber" which you can use to easily download 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 complete website for offline viewing.)
Blue Crab sports two types of "grabbers" for crawling a website. The first kind, called "classic" since it was the initial grabber type in Blue Crab, uses the original methods provided by the Mac OS for downloading URLs. The classic grabber shows very detailed progress statistics, and in particular the server's HTTP response headers in log format (which provides information like server type.) The alternative "quick" grabber is the newer type, and forms the basis of the "download one page" and "media" grabbers. The term "quick" comes from the fact this grabber uses newer Mac OS technology and doesn't provide as much progress statistics as the classic version. In benchmark testing it can be up to 20% faster. In addition, for certain websites, one type of grabber may yield better results than another.
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As an alternative to crawling a website sometimes you may just want to download a collection of independent URLs. You might be surfing the web and as you go along find relevent PDFs or images for, say, a research project. Using the batch downloader simply drag the URLs into the batch download window to collect them. When you are done just click the "Start" button to download them all at once.
Once you download a collection of files you can searcg them with the built in text search window, which display found result hierarchically:
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Finally, Blue Crab is gentle on the server. It processes only one URL at a time and may be configured to grab resources at preset time intervals. Considering the stress such programs can put on websites by downloading all of their content it is only fair that they do so in small increments over a longer periods of time. (If you've ever looked at your web logs you'll see that robots like Google are highly intermittent.)
A small tour is available that quickly introduces you to the many features of Blue Crab. If you would like to take the tour now click on the link below.
Major Features
Unique URL extraction algorithms yield very complete downloads compared to other products of this type.
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You can download web sites either for offline browsing, via re-linking of URL's, or to create virtual copies of them on your hard drive, i.e. backup a web site as-is.
Supports both HTTP, HTTPS protocols as well as server realms. Detailed Grabber window shows server HTTP header response fields.
Optionally display web pages as they are crawled using either your own web browser or Blue Crabs own web window.
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You can restrict a crawl to just the initial domain, or allow the program to "stray" into offsite URL's
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Blue Crab can remap "dynamic" URL's which contain path and search arguments so that resulting disk files are navigable offline.
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Image URL's into JPEG files (or any other graphic file type supported by Quicktime) to create complete pictures of web pages not possible simply by taking a single screen shot yourself.
Blue Crab provides its URL imaging ability as a service menu item available from other applications.
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URL's can be imaged into files, or onto the clipboard.
Built-in directory search displays found files as a hierarchical list, with double-clickable entries.
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A "batch window" enables you to download your own list of files. Simply drag and drop URL's into the batch window, or import them from an HTML file , or text file.
Grabbing in "images-only" mode just downloads image files, optionally "flattening" the results (i.e. putting all images into one folder.)
Reusable configuration settings control what is grabbed, saved or crawled:
- Filter by size, date, file type or even content
- Filter by filename, extension or path
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Bookmarks window for storing frequently crawled web sites
Supports form submissions to enable you to begin a crawl from a login page.
Supports cookies for more accurate downloads.
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Generate site maps that consist of a hierarchical display of URL's Such maps can be optionally filtered by extension.
Find email addresses.
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Customizable user-agent (spoofing) enables you to download web sites which are platform specific.
Optionally receive email notifications of Blue Crab's progress during a lengthy crawl.
Dock badging provides visual feedback or progress when the program is in the background.
Boolean Search and Blue Crab
You can use Blue Crab to download web sites and then index and search them with Boolean Search.
| Product | Rating | Downloads | |
|---|---|---|---|
| Blue Crab | add a comment | ||
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