To download a file and save the request and response data to a WARC file, run this: bash wget "http://www.archiveteam.org/" --warc-file="at"

Extracting a WARC record

Once we’ve identified the offset and length of a particular record (in this case, an offset of 1260 bytes and a length of 1085 bytes), we can snip out an individual record like this:

$ tail -c +1261 hello-world.warc | head -c 1085

Making the WARC

To create a WARC, we used wget:

$ wget --warc-file hello-world http://iipc.github.io/warc-specifications/primers/web-archive-formats/hello-world.txt

…which created the compressed hello-world.warc.gz file. These special block-compressed files are often used directly, but in this primer, we uncompress it so we can see what’s going on:

$ gunzip hello-world.warc.gz

…leaving us with hello-world.warc.

import warc

from StringIO import StringIO
from httplib import HTTPResponse

class FakeSocket():
    def __init__(self, response_str):
        self._file = StringIO(response_str)
    def makefile(self, *args, **kwargs):
        return self._file

for record in warc.open("eada.warc.gz"):
    if record.type == "response":
        resp = HTTPResponse(FakeSocket(record.payload.read()))
        resp.begin()
        if resp.getheader("content-type") == "text/html":
            print record['WARC-Target-URI']

I sorted the output and came up with a nice list of URLs for the website. Here is a brief snippet:

http://mith.umd.edu/eada/gateway/winslow.php
http://mith.umd.edu/eada/gateway/winthrop.php
http://mith.umd.edu/eada/gateway/witchcraft.php
http://mith.umd.edu/eada/gateway/wood.php
http://mith.umd.edu/eada/gateway/woolman.php
http://mith.umd.edu/eada/gateway/yeardley.php
http://mith.umd.edu/eada/guesteditors.php
http://mith.umd.edu/eada/html/display.php?docs=acrelius_founding.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=alsop_character.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=arabic.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=ashbridge_account.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=banneker_letter.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=barlow_anarchiad.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=barlow_conspiracy.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=barlow_vision.xml&action=show
http://mith.umd.edu/eada/html/display.php?docs=barlowe_voyage.xml&action=show

$ wget --warc-file eada --mirror --page-requisites --adjust-extension --convert-links --wait 1 --execute robots=off --no-parent http://mith.umd.edu/eada/ > /dev/null 
WARC output does not work with timestamping, timestamping will be disabled.
Opening WARC file ‘eada.warc.gz’.

--2021-12-29 17:43:08--  http://mith.umd.edu/eada/
Resolving mith.umd.edu (mith.umd.edu)... 174.129.6.250
Connecting to mith.umd.edu (mith.umd.edu)|174.129.6.250|:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://mith.umd.edu/eada/ [following]

     0K                                                       100% 25,6M=0s

--2021-12-29 17:43:10--  https://mith.umd.edu/eada/
Connecting to mith.umd.edu (mith.umd.edu)|174.129.6.250|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://archive.mith.umd.edu/eada/ [following]

     0K                                                       100% 41,1M=0s

--2021-12-29 17:43:11--  https://archive.mith.umd.edu/eada/
Resolving archive.mith.umd.edu (archive.mith.umd.edu)... 174.129.6.250
Connecting to archive.mith.umd.edu (archive.mith.umd.edu)|174.129.6.250|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://eada.lib.umd.edu [following]

     0K                                                       100% 42,9M=0s

--2021-12-29 17:43:13--  http://eada.lib.umd.edu/
Resolving eada.lib.umd.edu (eada.lib.umd.edu)... 129.2.19.174
Connecting to eada.lib.umd.edu (eada.lib.umd.edu)|129.2.19.174|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 5210 (5,1K) [text/html]
Saving to: ‘mith.umd.edu/eada/index.html’

     0K .....                                                 100%  447M=0s

2021-12-29 17:43:13 (447 MB/s) - ‘mith.umd.edu/eada/index.html’ saved [5210/5210]

FINISHED --2021-12-29 17:43:13--
Total wall clock time: 5,2s
Downloaded: 1 files, 5,1K in 0s (447 MB/s)
Converting links in mith.umd.edu/eada/index.html... 2-7
Converted links in 1 files in 0,001 seconds.

WET Response Format

As many tasks only require textual information, the CommonCrawl dataset provides WET files that only contain extracted plaintext. The way in which this textual data is stored in the WET format is quite simple. The WARC metadata contains various details, including the URL and the length of the plaintext data, with the plaintext data following immediately afterwards.

WARC/1.0
WARC-Type: conversion
WARC-Target-URI: http://advocatehealth.com/condell/emergencyservices3
WARC-Date: 2013-12-04T15:30:35Z
WARC-Record-ID: 
WARC-Refers-To: 
WARC-Block-Digest: sha1:3SJBHMFPOCUJEHJ7OMGVCRSHQTWLJUUS
Content-Type: text/plain
Content-Length: 5765


...Text Content...

WAT Response Format

WAT files contain important metadata about the records stored in the WARC format above. This metadata is computed for each of the three types of records (metadata, request, and response). If the information crawled is HTML, the computed metadata includes the HTTP headers returned and the links (including the type of link) listed on the page.

This information is stored as JSON. To keep the file sizes as small as possible, the JSON is stored with all unnecessary whitespace stripped, resulting in a relatively unreadable format for humans. If you want to inspect the JSON file yourself, use one of the many JSON pretty print tools available.

The HTTP response metadata is most likely to be of interest to CommonCrawl users. The skeleton of the JSON format is outlined below.

    Envelope
        WARC-Header-Metadata
        Payload-Metadata
            HTTP-Response-Metadata
                Headers
                    HTML-Metadata
                        Head
                            Title
                            Scripts
                            Metas
                            Links
                        Links
        Container

WARC Format

The WARC format is the raw data from the crawl, providing a direct mapping to the crawl process. Not only does the format store the HTTP response from the websites it contacts (WARC-Type: response), it also stores information about how that information was requested (WARC-Type: request) and metadata on the crawl process itself (WARC-Type: metadata).

For the HTTP responses themselves, the raw response is stored. This not only includes the response itself, what you would get if you downloaded the file, but also the HTTP header information, which can be used to glean a number of interesting insights.

In the example below, we can see the crawler contacted http://102jamzorlando.cbslocal.com/tag/nba/page/2/ and received a HTML page in response. We can also see the page was served from the nginx web server and that a special header has been added, X-hacker, purely for the purposes of advertising to a very specific audience of programmers who might look at the HTTP headers!

WARC/1.0
WARC-Type: response
WARC-Date: 2013-12-04T16:47:32Z
WARC-Record-ID: 
Content-Length: 73873
Content-Type: application/http; msgtype=response
WARC-Warcinfo-ID: 
WARC-Concurrent-To: 
WARC-IP-Address: 23.0.160.82
WARC-Target-URI: http://102jamzorlando.cbslocal.com/tag/nba/page/2/
WARC-Payload-Digest: sha1:FXV2BZKHT6SQ4RZWNMIMP7KMFUNZMZFB
WARC-Block-Digest: sha1:GMYFZYSACNBEGHVP3YFQNOSTV5LPXNAU

HTTP/1.0 200 OK
Server: nginx
Content-Type: text/html; charset=UTF-8
Vary: Accept-Encoding
Vary: Cookie
X-hacker: If you're reading this, you should visit automattic.com/jobs and apply to join the fun, mention this header.
Content-Encoding: gzip
Date: Wed, 04 Dec 2013 16:47:32 GMT
Content-Length: 18953
Connection: close


...HTML Content...