Common Crawl builds an open dataset containing over 100 billion unique items downloaded from the internet. Every month they use Apache Nutch to follow links accross the web and download over a billion unique items to Amazon S3, and have data back to 2008. This is like what Google and Bing do to build their search engines, the difference being that Common Crawl provides their data to the world for free.

But how do you find for a particular webpage in petabytes of data? Common Crawl provides two types of indexes for this: the Common Crawl Capture Index (CDX) and the Columnar Index. This article talks about the CDX Index Server and a future article will talk about the more powerful columnar index.

Common Crawl tries to do a broad search, getting a wide sample of the web rather than a deep sample of a few webistes, and respects robots.txt so not every page will be in there. It's useful to know whether Common Crawl even contains the information you're looking before you start, and the index will tell you where to look.

This article covers using the web interface for quickly checking what's there, using cdx_toolkit to get and download results from the command line or Python, and using the index and fetching with HTTP requests for custom usecases. There are other tools as well like the CDX Index Client for command line use and comcrawl from python, but they seem less flexible than the other options.

See the corresponding Jupyter notebook (raw) for more code examples.

Using the Web Interface

Go to the Common Crawl Index Server and select a Search Page from the left column. Note that the crawl names are CC-MAIN-<YYYY>-<WW> where <YYYY>-<WW> is the crawl ISO 8601 Week Date. Then you can type your website and can have a wildcard at the end of the URL or in the domain. It will then return JSON lines of results showing the URLs and the metadata you need to find them.

For example in the 2020-16 crawl if I type* I get 43 results. I can see the first result is, that the HTTP status was 200 (it was successfully retrieved) and that the archived HTML is available in segment 1585370497042.33.

I could also look for all subdomains of a particular domain. For example Learn Bayes Stats has a website which is a subdomain of We can find other websites created with anvil by searching for * giving 48 results.

CDX Toolkit

CDX Toolkit gives a way to search the indexes of both Common Crawl and Internet Archive in a straightforward way. It provides a useful command line and Python interface, and is highly flexible and relatively straightforward to use. I would recommend it as a starting point with Common Crawl, but haven't tested it's speed on large amounts of data. It's easy to install with python -m pip install cdx_toolkit.

CDX Toolkit in the Command Line

You can use it from the command line with cdxt. You can specify a range of dates in the form YYYYMM (not weeks like in the index files!), and whether to return a CSV (default) or lines of JSON:

cdxt --cc --from 202002 --to 202005 iter \

You can pass other arguments to filter the result or customise the fields returned. Here's an example to count the number of archived pages in dataisbeautiful fetched with 200 OK status between Feb and May 2020 (I removed query parameters with sed because here they are just tracking tags).

cdxt --cc --from 202002 --to 202005 \
     --filter '=status:200' iter \
     '*' \
     --fields url | \
  sed 's/\?.*//' | \
  sort -u | \
  wc -l

You can easily switch from Common Crawl with -cc to the Internet Archive's Wayback Machine with -ia (but it doesn't support all the same filters).

cdxt --ia --from 202002 --to 202005 iter \

You can download the Web Archive content using the warc subcommand.

cdxt --cc --from 202002 --to 202005 \
     --filter '=status:200' --limit 10 warc \
     --prefix DATAISBEAUTIFUL \

A bunch of Nones get printed to the screen and produces a file DATAISBEAUTIFUL-000000.extracted.warc.gz. A WARC is essentially the HTML preceeded by some headers containing metadata about the request and the response. It's simple enough that you could parse it manually, or you could use the Python warcio library.

Sample of WARC Output

CDX Toolkit in Python

You can also use the CDX Toolkit as a library in Python. The API for the CDXFetcher is similar to the CLI except from becomes from_ts:

import cdx_toolkit
cdx = cdx_toolkit.CDXFetcher(source='cc')
objs = list(cdx.iter(url, from_ts='202002', to='202006', 
                     limit=5, filter='=status:200'))
[ for o in objs]
urlkey timestamp status mime url languages filename length charset digest offset mime-detected
com,reddit)/r/dataisbeautiful/comments/718wt7/heatmap_of_my_location_during_last_2_years_living 20200330143847 200 text/html eng crawl-data/CC-MAIN-2020-16/segments/1585370497042.33/warc/CC-MAIN-20200330120036-20200330150036-00407.warc.gz 69934 UTF-8 K7RHDCY4H6XIAFL7SLFTMUV76XFOEM7K 1143289534 text/html
com,reddit)/r/dataisbeautiful/comments/7wcyiq/this_is_what_8_months_of_roulette_looks_like_oc 20200408190429 200 text/html eng crawl-data/CC-MAIN-2020-16/segments/1585371821680.80/warc/CC-MAIN-20200408170717-20200408201217-00043.warc.gz 85936 UTF-8 3VQ6OENLZIZGFNY7X3TIYNOYMGLABZFR 1099976248 text/html
com,reddit)/r/dataisbeautiful/comments/c89mz2/battle_dataviz_battle_for_the_month_of_july_2019/eskzdhd 20200403174615 200 text/html eng crawl-data/CC-MAIN-2020-16/segments/1585370515113.54/warc/CC-MAIN-20200403154746-20200403184746-00236.warc.gz 23114 UTF-8 IS4SLLIK7QHNEAJ23E7H4H5ZK2HEMME3 1080275232 text/html
com,reddit)/r/dataisbeautiful/comments/csl706/i_recorded_my_travels_as_a_professional_truck 20200404003226 200 text/html eng crawl-data/CC-MAIN-2020-16/segments/1585370518767.60/warc/CC-MAIN-20200403220847-20200404010847-00342.warc.gz 81851 UTF-8 3BP6SQLMDA3EHICA5TRBNFBCRNDPEOLT 1106586323 text/html
com,reddit)/r/dataisbeautiful/comments/dp5tda/oc_i_cycled_through_all_the_streets_central_london 20200331141918 200 text/html eng crawl-data/CC-MAIN-2020-16/segments/1585370500482.27/warc/CC-MAIN-20200331115844-20200331145844-00166.warc.gz 79999 UTF-8 POVTU3VOPDUU2CAB2OWZTTBVYGM7HMFX 1104520094 text/html

The raw archived HTML can be retrieved with .content:

from bs4 import BeautifulSoup
html = objs[0].content
soup = BeautifulSoup(html, 'lxml')

You can also get the warcio object with .warc_record


Using the index directly

The Capture Index (CDX) API is just a HTTP endpoint for a compressed text file giving describing the underlying Web Archives. Common Crawl use pywb to serve the index and have a great introductory blog post to CDX. You can access it directly with curl or the Python requests library.

Doing it yourself you have to find the right collections, deal with pagination and retrieve and decompress the content. This is what CDX toolkit handles for you, but sometimes it might be useful to do it directly.

Getting the available collections

First we need to know what indexes are available; this is stored in a JSON file called collinfo.json.

cdx_indexes = requests.get('').json()

This contains JSON data with the id, description, and API locations for each crawl.

id name timegate cdx-api
CC-MAIN-2020-24 May 2020 Index
CC-MAIN-2020-16 March 2020 Index
CC-MAIN-2020-10 February 2020 Index
CC-MAIN-2020-05 January 2020 Index
CC-MAIN-2019-51 December 2019 Index
... ... ... ...
CC-MAIN-2008-2009 Index of 2008 - 2009 ARC files

If we want to look through multiple collections we would have to query each API endpoint separately. Note that really old indexes use a different id format with a range of years.

Let's pick the most recent crawl's API endpoint.

api_url = cdx_indexes[0]['cdx-api']

Simple CDX Query

We can then use the cdx-api URL to query the relevant indexes.

r = requests.get(api_url,
                 params = {
                     'url': '',
                     'limit': 10,
                     'output': 'json'
records = [json.loads(line) for line in r.text.split('\n') if line]

The JSON records look the same as

urlkey timestamp offset status languages digest length mime-detected filename charset mime url redirect
com,reddit)/ 20200525024432 873986269 200 eng C6Y4VCGYLE3NGEWLJNONES6JMNA74IA3 40851 text/html crawl-data/CC-MAIN-2020-24/segments/1590347387155.10/warc/CC-MAIN-20200525001747-20200525031747-00335.warc.gz UTF-8 text/html nan
com,reddit)/ 20200526071834 787273867 200 eng PHMHCKU365PLDN5UQETZVR4UGMSPDXQJ 42855 text/html crawl-data/CC-MAIN-2020-24/segments/1590347390448.11/warc/CC-MAIN-20200526050333-20200526080333-00335.warc.gz UTF-8 text/html nan
com,reddit)/ 20200526163829 3815970 200 nan X67YXUXXE5GQPMJKMEE6555BNFPIER7L 35345 text/html crawl-data/CC-MAIN-2020-24/segments/1590347391277.13/robotstxt/CC-MAIN-20200526160400-20200526190400-00048.warc.gz nan text/html nan
com,reddit)/ 20200526165552 879974740 200 eng OSGHIVCFBI47ZSNMLG574K6SBZJ3LTBC 39146 text/html crawl-data/CC-MAIN-2020-24/segments/1590347391277.13/warc/CC-MAIN-20200526160400-20200526190400-00335.warc.gz UTF-8 text/html nan
com,reddit)/ 20200527211917 858583595 200 eng UHM2VERG5OUOELJFD7O25JVUBZVDPDLU 35751 text/html crawl-data/CC-MAIN-2020-24/segments/1590347396163.18/warc/CC-MAIN-20200527204212-20200527234212-00335.warc.gz UTF-8 text/html nan

Of course you can also query the endpoin directly with curl to get the JSON lines:

curl ''

Adding filters and options

We can add additional options like filters and selecting fields, in the same way exposed by cdx_toolkit. Here we filter to results with a status of 200, that were detected to have mime text/html and that have a URL matching the regex .*/comments/ (so have /comments/ somewhere in the URL).

r = requests.get(api_url,
                 params = {
                     'url': '*',
                     'limit': 10,
                     'output': 'json',
                     'fl': 'url,filename,offset,length',
                     'filter': ['=status:200', 
records = [json.loads(line) for line in r.text.split('\n') if line]

Handling zero results

When there are no results then the response is a 404 with a JSON error message "No Captures found ...".

r = requests.get(api_url,
                 params = {
                     'url': '*',
                     'output': 'json',
r.status_code  # 404
r.json()       # {'error': 'No Captures found for:*'}

Dealing with Pagination

The Common Crawl API by default returns around 15,000 records per page (it's 5 compressed blocks, which can vary in the number of actual records). You can choose the number of compressed blocks it returns (about 3,000 records per block) with pageSize and the page number with page.

To find the total number of pages you can use the showNumPages=True parameter, which gives back a JSON object containing the pageSize, blocks (total compressed blocks of data) and pages to return. The pageSize is in blocks, so pages = math.ceil(blocks/pageSize).

r = requests.get(api_url,
                 params = {
                     'url': '*',
                     'output': 'json',
                     'showNumPages': True,
r.json()  # {'pageSize': 5, 'blocks': 2044, 'pages': 409}

You can then iterate from page 0 to pages - 1.

r = requests.get(api_url,
                 params = {
                     'url': '*',
                     'output': 'json',
                     'page': 2,

When you go past the end of the pages you will get a HTTP 400 error response. You could use this to avoid having to ask the number of pages up front, just iterate until you get an error.

r = requests.get(api_url,
                 params = {
                     'url': '*',
                     'output': 'json',
                     'page': 409,
r.status_code   # 400

The response includes information telling you what went wrong (r.text):

<!DOCTYPE html>
<link rel="stylesheet" href="/static/__shared/shared.css"/>
<h2>Common Crawl Index Server Error</h2>
<b>Page 409 invalid: First Page is 0, Last Page is 408</b>


Retrieving Content

The CDX queries return a filename which is on S3 and accessible at They also contain a offset and length which tells you where in bytes the record data is and how long it is. We can use a Range header to get just this data (since each whole file is around 1GB).

record = records[0]
prefix_url = ''
data_url = prefix_url + record['filename']
start_byte = int(record['offset'])
end_byte = start_byte + int(record['length'])
headers = {'Range': f'bytes={start_byte}-{end_byte}'}
r = requests.get(data_url, headers=headers)

We then have to decompress the data since it is gzipped. The gzip library only works on files with headers, so we have to decompress using zlib. We need to set wbits to the right value for gzip, otherwise we get Error -3 while decompressing data: incorrect header check.

import zlib
data = zlib.decompress(r.content, wbits = zlib.MAX_WBITS | 16)

This then gives the WARC request headers, HTTP response headers and full HTML retrieved (I've truncated the output because there's a lot of HTML):

WARC-Type: response
WARC-Date: 2020-05-25T02:44:32Z
WARC-Record-ID: <urn:uuid:fa7c243e-d055-469b-bb4f-aa8580bc8330>
Content-Length: 238774
Content-Type: application/http; msgtype=response
WARC-Warcinfo-ID: <urn:uuid:2a234f6f-6796-4962-8c6f-84a6fe8b8945>
WARC-Concurrent-To: <urn:uuid:b7ec4524-bc4a-4da1-906b-6c53f9c9836e>
WARC-Identified-Payload-Type: text/html

HTTP/1.1 200 OK
Connection: keep-alive
X-Crawler-Content-Length: 41748
Content-Length: 237219
Content-Type: text/html; charset=UTF-8
x-ua-compatible: IE=edge
x-frame-options: SAMEORIGIN
x-content-type-options: nosniff
x-xss-protection: 1; mode=block
X-Crawler-Content-Encoding: gzip
cache-control: max-age=0, must-revalidate
X-Moose: majestic
Accept-Ranges: bytes
Date: Mon, 25 May 2020 02:44:32 GMT
Via: 1.1 varnish
X-Served-By: cache-wdc5543-WDC
X-Cache: MISS
X-Cache-Hits: 0
X-Timer: S1590374672.949570,VS0,VE950
Vary: accept-encoding
Set-Cookie: loid=00000000006kkgzyec.2.1590374671996.Z0FBQUFBQmV5ekVRNHBWX0ZOM3RJb0FRX0FHRzVzNVdlMXY2ejUwdFBxeHJkczRtLUlNR2o1SUxNUGlhSU12WnBsSjFfdmNkYl9fTm9GSUk2SHJHTmdmejUwblMzcnBESm0yZVlYUXBmekNqTVNuQXRTOUpHRndXek9zS1pvVVJxN05HdmVBUmFXZUI;; Max-Age=63071999; Path=/; expires=Wed, 25-May-2022 02:44:32 GMT; secure; SameSite=None; Secure
Set-Cookie: session_tracker=LwR2XV8052i86pF3B7.0.1590374671996.Z0FBQUFBQmV5ekVRZ2tNSkRpM0ZsYUlLcVJtRFBfOXRsREVCRlRPWElkRFpIUkJtODl3dnpnaDloZDM1NXplM0xMZEZialZxT0RhR250cEtTTTdfbXAyT2dqWGYyVVlSOV9TQ2paLUpITWloVkRibGw1SzhyMGo3b0RCdVhNT0tuN0pZSWU3ZE45Nkc;; Max-Age=7199; Path=/; expires=Mon, 25-May-2020 04:44:32 GMT; secure; SameSite=None; Secure
Set-Cookie: csv=1; Max-Age=63072000;; Path=/; Secure; SameSite=None
Set-Cookie: edgebucket=gwfpIQWim0qQ1ddmdP;; Max-Age=63071999; Path=/;  secure
Strict-Transport-Security: max-age=15552000; includeSubDomains; preload
Server: snooserv

<!doctype html><html xmlns="" lang="en" xml:lang="en"><head><title>reddit: the front page of the internet</title><meta name="keywords" content=" reddit,, vote, comment, submit " /><meta name="description" content="Reddit gives you the best of the internet in one place. Get a constantly updating feed of breaking news, fun stories, pics, memes, and videos...

Searching and fetching with Python and comcrawl

The comcrawl library makes it easy to search the index and download the data. The interface is a bit simpler than cdx_toolkit, but it doesn't allow you to pass filters, query the Internet Archive Wayback Machine, or retrieve the request/response metadata. You can install it with python -m pip install commcrawl.

You create an IndexClient with the indexes you want to search and call search

from comcrawl import IndexClient
# Only get results from these two crawls
# Passing no arguments does all crawls
client = IndexClient(['2020-10', '2020-16'])
# If using lots of indexes increase threads to speed it up'*', threads=1)

Then client.results is a list of dictionaries containing the data from the CDX. Here's the first few results in tabular form.

urlkey timestamp status mime url filename length redirect digest offset mime-detected languages charset
com,reddit)/r/dataisbeautiful/comments/2wlsvz/why_the_mlb_rule_changes_since_2004_game_time_is 20200217065457 301 unk crawl-data/CC-MAIN-2020-10/segments/1581875141749.3/crawldiagnostics/CC-MAIN-20200217055517-20200217085517-00493.warc.gz 679 3I42H3S6NNFQ2MSVX7XZKYAYSCX5QBYJ 13689701 application/octet-stream nan nan
com,reddit)/r/dataisbeautiful/comments/2wlsvz/why_the_mlb_rule_changes_since_2004_game_time_is 20200217065459 200 text/html crawl-data/CC-MAIN-2020-10/segments/1581875141749.3/warc/CC-MAIN-20200217055517-20200217085517-00108.warc.gz 74716 nan L4C22PRVUOGG22PXMKSB7KYVCWQUKEQ7 915522267 text/html eng UTF-8
com,reddit)/r/dataisbeautiful/comments/7f2sfy/natural_language_processing_techniques_used_to/dq9qzkh 20200223060640 200 text/html crawl-data/CC-MAIN-2020-10/segments/1581875145746.24/warc/CC-MAIN-20200223032129-20200223062129-00153.warc.gz 29470 nan GEWEQE4I2JOSKTL3QXPEI7FXVI3BP52O 884674375 text/html eng UTF-8
com,reddit)/r/dataisbeautiful/comments/7jbefu/four_years_of_initial_coin_offerings_in_one 20200217195615 200 text/html crawl-data/CC-MAIN-2020-10/segments/1581875143079.30/warc/CC-MAIN-20200217175826-20200217205826-00313.warc.gz 21516 nan 42HZLBLZI5DQYGQAZNUAQ5NRCMEEVERW 890110347 text/html eng UTF-8
com,reddit)/r/dataisbeautiful/comments/8f1rk7/united_states_of_apathy_2016_us_presidential 20200222202649 200 text/html crawl-data/CC-MAIN-2020-10/segments/1581875145713.39/warc/CC-MAIN-20200222180557-20200222210557-00466.warc.gz 95956 nan IDKDLHSVB7YH3L2AUIMKPJFER3VLBZRU 859518253 text/html eng UTF-8

Notice that the first result has a status 301; let's filter to the first 2 ok results and download their data. The download method downloads every record in results and adds a html field with the raw HTML Common Crawl fetched.

client.results = [res for res in client.results if res['status'] == '200'][:2]

You can then process the HTML with beautifulsoup or even display it in a Jupyter notebook with IPython.display.HTML (though this may fetch a bunch of assets from the internet, and the CSS may make your notebook funny):

from IPython.display import HTML

Reddit Data is Beautiful post inside a Jupyter notebook