1. Luke Plant
  2. django-output-validator


django-output-validator /

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Django output validator

This app validates all the HTML (or potentially other data) that is generated by your Django project. This is meant to be used only in development.


  • Run setup.py to install the package into your python path, or use easy_install django-output-validator (or pip).

  • Add "output_validator" to your INSTALLED_APPS setting.

  • If you have removed "django.template.loaders.app_directories.Loader" from your TEMPLATE_LOADERS, you need to add the 'templates' folder to your TEMPLATE_DIRS setting.

  • Insert the middleware "output_validator.middleware.ValidatorMiddleware" near the beginning of the middleware list (which means it will get the the response object after everything else). It must be after every middleware that does post-processing, but mustn't be after GZip, since it can't handle gzipped HTML. ( I just disable the GZip middleware for development)

  • Alter your URL conf to include the URLs for the validator. You need this line inserted somewhere:

    (r'^validator/', include('output_validator.urls'))
  • Add a setting to tell the app where to find the 'validate' executable used for validation. This is a dictionary of mimetypes and corresponding validators, allowing this app to be extended to any other generated content:

      'text/html': '/usr/bin/validate',
      'application/xml+xhtml': '/usr/bin/validate',

    I usually use a small wrapper for this executable that pops up a message when it fails - the following works for GNOME (if you have the notify-send program installed):

    validate "$1" || {
        notify-send "Validation failed";
  • Finally, run the django admin script to set up the database tables:

    ./manage.py --settings="yourproject.settings" syncdb

    OR, if you are using South:

    ./manage.py --settings="yourproject.settings" migrate output_validator
  • Optionally, set the following settings:

    • OUTPUT_VALIDATOR_IGNORE_PATHS - this is a list of path prefixes that will be ignored. For example, if you have the admin at /admin/ you can ignore any errors in the admin with this:



When browsing any of your pages in development, all HTML will be validated. If it fails, it will be logged. You can see all failures at 'http://localhost:8000/validator/' (assuming local development and the URL conf suggested above). Use the app to delete old failures once they have been fixed.