A standard pipeline for running open source scanning tools on domains to measure things like speed, accessibiity, and HTTPS.
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A domain scanner

Scans domains for data on their HTTPS configuration and assorted other things.

Most of the work is farmed out to other command line tools. The point of this project is to coordinate those tools and produce consistent data output.

Can be used with any domain, or CSV where domains are the first column, such as the official .gov domain list.


The requirements here can be quite diverse, because this tool is just a coordinator for other tools. Communication between tools is handled via CLI and STDOUT.

The overall tool requires Python 3. To install dependencies:

pip install -r requirements.txt

The individual scanners each require their own dependencies. You only need to have the dependencies installed for the scanners you plan to use.

  • inspect scanner: Ruby and site-inspector, version 1.0.2 only.
  • pshtt scanner: Python 2 and pshtt, ideally installed with pyenv via pip install pshtt.
  • tls scanner: Go and ssllabs-scan, stable branch.
  • sslyze scanner: Python 2 and sslyze, ideally installed with pyenv via pip install sslyze.
  • pageload scanner: Node and phantomas, installed through npm.
Setting tool paths

By default, domain-scan will expect the paths to any executables to be on the system PATH.

If you need to point it to a local directory instead, you'll need to set environment variables to override this.

You can set environment variables in a variety of ways -- this tool's developers use autoenv to manage environment variables with a .env file.

However you set them:

  • Override the path to the site-inspector executable by setting the SITE_INSPECTOR_PATH environment variable.

  • Override the path to the ssllabs-scan executable by setting the SSLLABS_PATH environment variable.

  • Override the path to the sslyze.py executable by setting the SSLYZE_PATH environment variable. An env var of PYENV_VERSION=2.7.11 is passed by default, override version with SSLYZE_PYENV.

  • Override the path to the phantomas executable by setting the PHANTOMAS_PATH environment variable.


Scan a domain. You must specify at least one "scanner" with --scan.

./scan whitehouse.gov --scan=inspect

Scan a list of domains from a CSV. The CSV's header row will be ignored if the first cell starts with "Domain" (case-insensitive).

./scan domains.csv --scan=inspect

Run multiple scanners on each domain:

./scan whitehouse.gov --scan=inspect,tls

It's important to understand that scans run in parallel by default, and so the order of result data is unpredictable.

By default, each scanner will run up to 10 parallel tasks, which you can override with --workers.

Some scanners may limit this. For example, the tls scanner, which hits the SSL Labs API, maxes out at 5 tasks at once (which cannot be overridden with --workers).

To disable this and run sequentially through each domain (1 worker), use --serial.

Parallelization will also cause the resulting domains to be written in an unpredictable order. If the row order is important to you, disable parallelization, or use the --sort parameter to sort the resulting CSVs once the scans have completed. (Note: Using --sort will cause the entire dataset to be read into memory.)



  • inspect - HTTP/HTTPS/HSTS configuration.
  • pshtt - HTTP/HTTPS/HSTS configuration with the python-only pshtt tool.
  • tls - TLS configuration, using the SSL Labs API.
  • sslyze - TLS configuration, using the local sslyze command line tool.
  • analytics - Participation in an analytics program.
  • pageload - Page load and rendering metrics.
  • a11y - Accessibility data with the pa11y CLI tool via AWS Lambda (requires an AWS account and some additional setup, described further down this document).

General options:

  • --scan - Required. Comma-separated names of one or more scanners.
  • --sort - Sort result CSVs by domain name, alphabetically. (Note: this causes the entire dataset to be read into memory.)
  • --serial - Disable parallelization, force each task to be done simultaneously. Helpful for testing and debugging.
  • --debug - Print out more stuff. Useful with --serial.
  • --workers - Limit parallel threads per-scanner to a number.
  • --output - Where to output the cache/ and results/ directories. Defaults to ./.
  • --force - Ignore cached data and force scans to hit the network. For the tls scanner, this also tells SSL Labs to ignore its server-side cache.
  • --suffix - Add a suffix to all input domains. For example, a --suffix of virginia.gov will add .virginia.gov to the end of all input domains.

Scanner-specific options

  • --analytics - For the analytics scanner. Point this to either a file or a URL that contains a CSV of participating domains.


All output files are placed into cache/ and results/ directories, whose location defaults to the current directory (./). Override the output home with --output.

  • Cached full scan data about each domain is saved in the cache/ directory, named after each scan and each domain, in JSON.

Example: cache/inspect/whitehouse.gov.json

  • Formal output data in CSV form about all domains are saved in the results/ directory in CSV form, named after each scan.

Example: results/inspect.csv

You can override the output directory by specifying --output.

It's possible for scans to save multiple CSV rows per-domain. For example, the tls scan may have a row with details for each detected TLS "endpoint".

  • Scan metadata with the start time, end time, and scan command will be placed in the results/ directory as meta.json.

Example: results/meta.json

Using with Docker

If using Docker Compose, it is as simple as cloning this GitHub repository and running:

docker-compose up

Then to scan, prefix commands with docker-compose run, like:

docker-compose run scan <domain> --scan=<scanner>

Gathering hostnames

This tool also includes a facility for gathering domain names that end in a given suffix (e.g. .gov) from various sources.

By default, only fetches third-level and higher domains (excluding second-level domains).


./gather [source] [options]

Where source is one of:

  • censys - Walks the Censys.io API, which has hostnames gathered from observed certificates. Censys provides certificates observed from a nightly zmap scan of the IPv4 space, as well as certificates published to public Certificate Transparency logs.
  • url - Given a path to a CSV, reads it and applies deduping and filtering logic. Its only option is --url, which can be a URL (starts with http: or https:) or a local path.

General options:

  • --suffix: Required. suffix to filter on (e.g. .gov)
  • --parents: A path or URL to a CSV whose first column is second-level domains. Any subdomain not contained within these second-level domains will be excluded.
  • --include-parents: Include second-level domains. (Defaults to false.)
  • --debug: display extra output

censys: the Censys.io API

To configure, set two environment variables from your Censys account page:

  • CENSYS_UID: Your Censys API ID.
  • CENSYS_API_KEY: Your Censys secret.


  • --start: Page number to start on (defaults to 1)
  • --end: Page number to end on (defaults to value of --start)
  • --delay: Sleep between pages, to meet API limits. Defaults to 5s. If you have researcher access, shorten to 2s.


Find .gov certificates in the first 2 pages of Censys API results, waiting 5 seconds between pages:

./gather censys --suffix=.gov --start=1 --end=2 --delay=5

a11y setup

Because scanning 1,000+ domains with pa11y takes a prohibitively long time, we're relying on AWS Lambda to provide parallelization.

This requires:

1) An AWS account with access to Lambda 2) A pa11y-lambda function (follow the instructions here).

Once those are set up, copy the .env.example file, rename it .env and fill in the following values:

  • AWS_REGION_NAME (us-east-1 should work fine)
  • AWS_LAMBDA_PA11Y_FUNCTION_NAME (whatever you ended up naming the Lambda function)

A brief note on redirects:

For the accessibility scans we're running at 18F, we're using the inspect scanner to follow redirects before the accessibility scan runs. Pulse.cio.gov is set up to show accessibility scans for live, non-redirecting sites. For example, if aaa.gov redirects to bbb.gov, we will show results for bbb.gov on the site, but not aaa.gov.

However, if you want to include results for redirecting site, note the following. For example, if aaa.gov redirects to bbb.gov, pa11y will run against bbb.gov (but the result will be recorded for aaa.gov).

In order to get the benefits of the inspect scanner, all a11y scans must include it. For example, to scan gsa.gov:

./scan gsa.gov --scanner=inspect,a11y

Because of domain-scan's caching, all the results of an inspect scan will be saved in the cache/inspect folder, and probably does not need to be re-run for every single ally scan.

Public domain

This project is in the worldwide public domain. As stated in CONTRIBUTING:

This project is in the public domain within the United States, and copyright and related rights in the work worldwide are waived through the CC0 1.0 Universal public domain dedication.

All contributions to this project will be released under the CC0 dedication. By submitting a pull request, you are agreeing to comply with this waiver of copyright interest.