Blue Crab

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“Blue Crab ($25) is a versatile program that you use to copy the contents of a website to your computer, in whole or in part.

* Conduct fast offline browsing and searching without an internet connection.
* 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 own computer.
* Check a site for broken links, or generate an HTML site map
* Perform batch downloads of URLs
* Create full page images of URLs (JPEG, BMP, TIFF, PNG, PSD, etc.)”

When I first looked, briefly, at the background information to Blue Crab for some reason I thought it would be a really useful application for grabbing images off a web site for the reviews and articles that I write. What I had in mind was a smart way of grabbing, for example, an image on a site that was made up of a number of separate images, a logo for example. To that extent Blue Grab was a little disappointing, but only because it does so much more. Without wanting to do a disservice to the technical capabilities of the application (detailed below), in short it grabs everything that there is on a web site (or parts of if so desired) and creates a copy on your Mac. As a result it does exactly what I wanted it to do in that it is easy to find the image from the folder on the Mac and tidy it up.

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What I hadn’t realised was just how useful it would be to have a full version of a web site on the Macs hard drive – excellent for creating a presentation of Almerimar Life for potential sponsors, useful for continuing a review or writing a report when traveling and without access to the internet, or just to capture a site to safeguard against future changes.

Easy to set up and use, with an excellent Read Me section and good online Tour this is a well presented, well constructed and very useful application.

Technical Details

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 PDFs.

Blue Crab has a special feature called the “Image Grabber” which you can use to easily download just the graphics on a website. Moreover, you can view a slide show of the images as they are downloaded. You also have the option of “flattening” the images, i.e. putting them all into one folder, or preserving the folder structure on the server (just as when downloading a complete website for offline viewing.)

Starting with a single URL Blue Crab begins traversing the site by following the links on the HTML pages it finds. 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.

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.

Major Features

* Unique URL extraction algorithms yield very complete downloads compared to other products of this type.
* You can download websites either for offline browsing, via re-linking of URLs, or to create virtual copies of them on your hard drive, i.e. backup a website 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.
* You can restrict a crawl to just the initial domain, or allow the program to “stray” into offsite URLs.
* Blue Crab can remap “dynamic” URLs which contain path and search arguments so that resulting disk files are navigable offline.
* Image URLs 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 screenshot yourself.
* Blue Crab provides its URL imaging ability as a service menu item available from other applications.
* URLs can be imaged into files, or onto the clipboard.
* Built-in directory search displays found files as a hierarchical list, with double-clickable entries.
* A “batch window” enables you to download your own list of files. Simply drag and drop URLs 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:
o Filter by size, date, file type or even content
o Filter by filename, extension or path
* Bookmarks window for storing frequently crawled websites.
* Supports form submissions to enable you to begin a crawl from a login page.
* Supports cookies for more accurate downloads.
* Generate site maps that consist of a hierarchical display of URLs. Such maps can be optionally filtered by extension.
* Find email addresses.
* Customizable user-agent (spoofing) enables you to download websites 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.

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