Performance¶

Cache¶

We recommend Redis as a fast, persistent cache. Install Redis through your package manager (on Debian or Ubuntu: sudo apt-get install redis-server), add django-redis to your requirements.txt, and enable it as a cache backend:

CACHES = {
    'default': {
        'BACKEND': 'django_redis.cache.RedisCache',
        'LOCATION': 'redis://127.0.0.1:6379/dbname',
        # for django-redis < 3.8.0, use:
        # 'LOCATION': '127.0.0.1:6379',
        'OPTIONS': {
            'CLIENT_CLASS': 'django_redis.client.DefaultClient',
        }
    }
}

Caching image renditions¶

If you define a cache named ‘renditions’ (typically alongside your ‘default’ cache), Wagtail will cache image rendition lookups, which may improve the performance of pages which include many images.

CACHES = {
    'default': {...},
    'renditions': {
        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
        'LOCATION': '127.0.0.1:11211',
        'TIMEOUT': 600,
        'OPTIONS': {
            'MAX_ENTRIES': 1000
        }
    }
}

Image URLs¶

If all you need is the URL to an image (such as for use in meta tags or other tag attributes), it is likely more efficient to use the image serve view and {% image_url %} tag:

<meta property="og:image" content="{% image_url page.hero_image width-600 %}" />

Rather than finding or creating the rendition in the page request, the image serve view offloads this to a separate view, which only creates the rendition when the user requests the image (or returning an existing rendition if it already exists). This can drastically speed up page loads with many images. This may increase the number of requests handled by Wagtail if you’re using an external storage backend (for example Amazon S3).

Another side benefit is it prevents errors during conversation from causing page errors. If an image is too large for Willow to handle (the size of an image can be constrained with WAGTAILIMAGES_MAX_IMAGE_PIXELS), Willow may crash. As the resize is done outside the page load, the image will be missing, but the rest of the page content will remain.

The same can be achieved in Python using generate_image_url.

Search¶

Wagtail has strong support for Elasticsearch - both in the editor interface and for users of your site - but can fall back to a database search if Elasticsearch isn’t present. Elasticsearch is faster and more powerful than the Django ORM for text search, so we recommend installing it or using a hosted service like Searchly.

For details on configuring Wagtail for Elasticsearch, see Elasticsearch Backend.

Database¶

Wagtail is tested on PostgreSQL, SQLite and MySQL. It may work on some third-party database backends as well, but this is not guaranteed. We recommend PostgreSQL for production use.

Templates¶

The overhead from reading and compiling templates adds up. Django wraps its default loaders with cached template loader which stores the compiled Template in memory and returns it for subsequent requests. The cached loader is automatically enabled when DEBUG is False. If you are using custom loaders, update your settings to use it:

TEMPLATES = [{
    'BACKEND': 'django.template.backends.django.DjangoTemplates',
    'DIRS': [os.path.join(BASE_DIR, 'templates')],
    'OPTIONS': {
        'loaders': [
            ('django.template.loaders.cached.Loader', [
                'django.template.loaders.filesystem.Loader',
                'django.template.loaders.app_directories.Loader',
                'path.to.custom.Loader',
            ]),
        ],
    },
}]

Caching proxy¶

To support high volumes of traffic with excellent response times, we recommend a caching proxy. Both Varnish and Squid have been tested in production. Hosted proxies like Cloudflare should also work well.

Wagtail supports automatic cache invalidation for Varnish/Squid. See Frontend cache invalidator for more information.

Image attributes¶

For some images, it may be beneficial to lazy load images, so the rest of the page can continue to load. It can be configured site-wide Adding default attributes to all images or per-image More control over the img tag. For more details you can read about the loading='lazy' attribute and the 'decoding='async' attribute or this web.dev article on lazy loading images.

This optimisation is already handled for you for images in the admin site.