Prerender adheres to google's
_escaped_fragment_ proposal, which we recommend you use. It's easy:
- Just add <meta name="fragment" content="!"> to the <head> of all of your pages
- If you use hash urls (#), change them to the hash-bang (#!)
Prerender includes lots of plugins, for example using Amazon S3 to cache your prerendered HTML. Prerender also starts multiple phantomjs processes to maximize throughput.
This is a list of middleware available to use with the prerender service:
- prerender-node (Express)
- prerender_rails (Rails)
Request more middleware for a different framework in this issue.
How it works
This is a simple service that only takes a url and returns the rendered HTML (with all script tags removed).
Note: you should proxy the request through your server (using middleware) so that any relative links to CSS/images/etc still work.
If you are trying to test Prerender with your website on localhost, you'll have to run the Prerender server locally so that Prerender can access your local dev website.
If you are running the prerender service locally. Make sure you set your middleware to point to your local Prerender server with:
export PRERENDER_SERVICE_URL=<your local url>
$ git clone https://github.com/prerender/prerender.git $ cd prerender $ npm install $ node server.js // also supports heroku style invocation using foreman $ foreman start
Prerender will now be running on http://localhost:3000. If you wanted to start a web app that ran on say, http://localhost:8000, you can now visit the URL http://localhost:3000/http://localhost:8000 to see how your app would render in Prerender.
Keep in mind you will see 504s for relative URLs because the actual domain on that request is your prerender server. This isn't really an issue because once you proxy that request through the middleware, then the domain will be your website and those requests won't be sent to the prerender server. For instance if you want to see your relative URLS working visit
Deploying your own on heroku
$ git clone https://github.com/prerender/prerender.git $ cd prerender $ heroku create $ git push heroku master
If you are installing Prerender under a Windows environment and you encounter errors related to 'node-gyp', you may need to follow these additional steps: https://github.com/nodejs/node-gyp#installation
You can clone this repo and run
npm install prerender --save to create an express-like server with custom plugins
We use a plugin system in the same way that Connect and Express use middleware. Our plugins are a little different and we don't want to confuse the prerender plugins with the prerender middleware, so we opted to call them "plugins".
Plugins are in the
lib/plugins directory, and add functionality to the prerender service.
Each plugin can implement any of the plugin methods:
beforePhantomRequest(req, res, next)
onPhantomPageCreate(phantom, req, res, next)
afterPhantomRequest(req, res, next)
beforeSend(req, res, next)
You can enable the plugins in
server.js by uncommenting the corresponding lines.
If you want to only allow access to your Prerender server from authorized parties, enable the basic auth plugin.
You will need to add the
BASIC_AUTH_PASSWORD environment variables.
export BASIC_AUTH_USERNAME=prerender export BASIC_AUTH_PASSWORD=test
Then make sure to pass the basic authentication headers (password base64 encoded).
curl -u prerender:wrong http://localhost:1337/http://example.com -> 401 curl -u prerender:test http://localhost:1337/http://example.com -> 200
For example, if you rendered the HTML of an angular page but left the angular scripts in there, your browser would try to execute the angular routing and rendering on a page that no longer has any angular bindings.
This plugin implements the
beforeSend funtion, therefore cached HTML pages still contain scripts tags until they get served.
Add these tags in the
<head> of your page if you want to serve soft http headers. Note: Prerender will still send the HTML of the page. This just modifies the status code and headers being sent.
Example: telling prerender to server this page as a 404
<meta name="prerender-status-code" content="404">
Example: telling prerender to serve this page as a 302 redirect
<meta name="prerender-status-code" content="302"> <meta name="prerender-header" content="Location: http://www.google.com">
If you only want to allow requests to a certain domain, use this plugin to cause a 404 for any other domains.
You can add the whitelisted domains to the plugin itself, or use the
ALLOWED_DOMAINS environment variable.
If you want to disallow requests to a certain domain, use this plugin to cause a 404 for the domains.
You can add the blacklisted domains to the plugin itself, or use the
BLACKLISTED_DOMAINS environment variable.
GET request will check S3 for a cached copy. If a cached copy is found, it will return that. Otherwise, it will make the request to your server and then persist the HTML to the S3 cache.
POST request will skip the S3 cache. It will make a request to your server and then persist the HTML to the S3 cache. The
POST is meant to update the cache.
You'll need to sign up with Amazon Web Services and export these 3 environment variables.
$ export AWS_ACCESS_KEY_ID=<aws access key> $ export AWS_SECRET_ACCESS_KEY=<aws secret access key> $ export S3_BUCKET_NAME=<bucket name>
Warning! Your keys should be kept private and you'll be charged for all files uploaded to S3.
If Prerender is hosted on a EC2 instance, you can also take advantage of IAM instance roles so that you don't need to export your AWS credentials.
You can also export the S3_PREFIX_KEY variable so that the key (which is by default the complete requested URL) is prefixed. This is useful if you want to organize the snapshots in the same bucket.
By default, s3HtmlCache works with the US Standard region (East), if your bucket is localized in another region you can config it with an environment variable :
$ export AWS_REGION=<region name>
For example :
$ export AWS_REGION=eu-west-1
Note The in memory cache is per process so if you have multiple Prerender workers then they do not share a cache. For higher traffic websites, use a common cache like redis.
An in memory cache but you can easily change it to any caching system compatible with the
cache-manager nodejs package.
For example, with the request:
First time: Overall Elapsed: 00:00:03.3174661
With cache: Overall Elapsed: 00:00:00.0360119
This will show console.log's from the phantomjs page in your local console. Great for debugging.
The MIT License (MIT)
Copyright (c) 2013 Todd Hooper <firstname.lastname@example.org>
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.