How to send requests to Splash HTTP API?

The recommended way is to use application/json POST requests, because this way you can preserve data types, and there is no limit on request size.

Python, using requests library

requests library is a popular way to send HTTP requests in Python. It provides a shortcut for sending JSON POST requests. Let’s send a simple Lua script to run endpoint:

import requests

script = """
return splash:png()
resp = requests.post('http://localhost:8050/run', json={
    'lua_source': script,
    'url': 'http://example.com'
png_data = resp.content

Python + Scrapy

Scrapy is a popular web crawling and scraping framework. For Scrapy + Splash integration use scrapy-splash library.

R language

There is a third-party library which makes it easy to use Splash in R language: https://github.com/hrbrmstr/splashr


curl --header "Content-Type: application/json" \
     -X POST \
     --data '{"url":"http://example.com","wait":1.0}' \


httpie is a command-line utility for sending HTTP requests; it has a nice API for sending for JSON POST requests:

http POST localhost:8050/render.png url=http://example.com width=200 > img.png


You can embed Splash results directly in HTML pages. This is not the best, as you’ll be rendering the website each time this HTML page is opened. But still, you can do this:

<img src="http://splash-url:8050/render.jpeg?url=http://example.com&width=300"/>

I’m getting lots of 504 Timeout errors, please help!

HTTP 504 error means a request to Splash took more than timeout seconds to complete (30s by default) - Splash aborts script execution after the timeout. To override the timeout value pass ‘timeout’ argument to the Splash endpoint you’re using.

Note that the maximum allowed timeout value is limited by the maximum timeout setting, which is by default 60 seconds. In other words, by default you can’t pass ?timeout=300 to run a long script - an error will be returned.

Maximum allowed timeout can be increased by passing --max-timeout option to Splash server on startup (see Passing Custom Options):

$ docker run -it -p 8050:8050 scrapinghub/splash --max-timeout 3600

If you’ve installed Splash without Docker, use

$ python3 -m splash.server --max-timeout 3600

The next question is why a request can need 10 minutes to render. There are 3 common reasons:

1. Slow website

A website can be really slow, or it can try to get some remote resources which are really slow.

There is no way around increasing timeouts and reducing request rate if the website itself is slow. However, often the problem lays in unreliable remote resources like third-party trackers or advertisments. By default Splash waits for all remote resources to load, but in most cases it is better not to wait for them forever.

To abort resource loading after a timeout and give the whole page a chance to render use resource timeouts. For render.*** endpoints use ‘resource_timeout’ argument; for execute or run use either splash.resource_timeout or request:set_timeout (see splash:on_request).

It is a good practive to always set resource_timeout; something similar to resource_timeout=20 often works well.

2. Splash Lua script does too many things

When a script fetches many pages or uses large delays then timeouts are inevitable. Sometimes you have to run such scripts; in this case increase --max-timeout Splash option and use larger timeout values.

But before increasing the timeouts consider splitting your script into smaller steps and sending them to Splash individually. For example, if you need to fetch 100 websites, don’t write a Splash Lua script which takes a list of 100 URLs and fetches them - write a Splash Lua script that takes 1 URL and fetches it, and send 100 requests to Splash. This approach has a number of benefits: it makes scripts more simple and robust and enables parallel processing.

3. Splash instance is overloaded

When Splash is overloaded it may start producing 504 errors.

Splash renders requests in parallel, but it doesn’t render them all at the same time - concurrency is limited to a value set at startup using --slots option. When all slots are used a request is put into a queue. The thing is that a timeout starts to tick once Splash receives a request, not when Splash starts to render it. If a request stays in an internal queue for a long time it can timeout even if a website is fast and splash is capable of rendering the website.

To increase rendering speed and fix an issue with a queue it is recommended to start several Splash instances and use a load balancer capable of maintaining its own request queue. HAProxy has all necessary features; check an example config here. A shared request queue in a load balancer also helps with reliability: you won’t be loosing requests if a Splash instance needs to be restarted.


Nginx (which is another popular load balancer) provides an internal queue only in its commercial version, Nginx Plus.

How to run Splash in production?

Easy Way

If you want to get started quickly take a look at Aquarium (which is a Splash setup without many of the pitfalls) or use a hosted solution like ScrapingHub’s.

Don’t forget to use resource timeous in your client code (see 1. Slow website). It also makes sense to retry a couple of times if Splash returns 5xx error response.

Hard Way

If you want to create your own production setup, here is a small non-exhaustive checklist:

  • Splash should be daemonized and started on boot;
  • in case of failures or segfaults Splash must be restarted;
  • memory usage should be limited;
  • several Splash instances should be started to use all CPU cores and/or multiple servers;
  • requests queue should be moved to the load balancer to make rendering more robust (see 3. Splash instance is overloaded).

Of course, it is also good to setup monitoring, configuration management, etc. - all the usual stuff.

To daemonize Splash, start it on boot and restart on failures one can use Docker: since Docker 1.2 there are --restart and -d options which can be used together. Another way to do that is to use standard tools like upstart, systemd or supervisor.


Docker --restart option won’t work without -d.

Splash uses an unbound in-memory cache and so it will eventually consume all RAM. A workaround is to restart the process when it uses too much memory; there is Splash --maxrss option for that. You can also add Docker --memory option to the mix.

In production it is a good idea to pin Splash version - instead of scrapinghub/splash it is usually better to use something like scrapinghub/splash:2.0.

A command for starting a long-running Splash server which uses up to 4GB RAM and daemonizes & restarts itself could look like this:

$ docker run -d -p 8050:8050 --memory=4.5G --restart=always scrapinghub/splash:3.1 --maxrss 4000

You also need a load balancer; for example configs check Aquarium or an HAProxy config in Splash repository.

Ansible Way

Ansible role for Splash is available via third-party project: https://github.com/nabilm/ansible-splash.

Website is not rendered correctly

Sometimes websites are not rendered correctly by Splash. Common reasons:

  • not enough wait time; solution - wait more (see e.g. splash:wait);
  • non-working localStorage in Private Mode. This is a common issue e.g. for websites based on AngularJS. If rendering doesn’t work, try disabling Private mode (see How do I disable Private mode?).
  • Sometimes content is lazy-loaded, or loaded only in a response for user actions (e.g. page scrolling). Try increasing viewport size to make everything visible, and waiting a bit after that (see splash:set_viewport_full). You may also have to simulate mouse and keyboard events (see Interacting with a page).
  • Missing features in WebKit used by Splash. Splash now uses https://github.com/annulen/webkit, which is much more recent than WebKit provided by Qt; we’ll be updating Splash WebKit as annulen’s webkit develops.
  • Qt or WebKit bugs which cause Splash to hang or crash. Often the whole website works, but some specific .js (or other) file causes problems. In this case you can try starting splash in verbose mode (e.g. docker run -it -p8050:8050 scrapinghub/splash -v2), noting what resources are downloaded last, and filtering them out using splash:on_request or Request Filters.
  • Some of the crashes can be solved by disabling HTML 5 media (splash.html5_media_enabled property or html5_media HTTP API argument) - note it is disabled by default.
  • Website may show a different content based on User-Agent header or based on IP address. Use splash:set_user_agent to change the default User-Agent header. If you’re running Splash in a cloud and not getting good results, try reproducing it locally as well, just in case results depend on IP address.
  • Website requires Flash. You can enable it using splash.plugins_enabled.
  • Website requires IndexedDB. Enable it using splash.indexeddb_enabled.
  • If there is no video or other media, use html5_media Splash HTTP argument or splash.html5_media_enabled property to enable HTML5 media, or splash.plugins_enabled to enable Flash.
  • Website has compatibility issues with Webkit version Splash is using. A quick (though not precise) way to check it is to try opening a page in Safari.

If you have troubles making Splash work, consider asking a question at https://stackoverflow.com. If you think it is a Splash bug, raise an issue at https://github.com/scrapinghub/splash/issues.

How do I disable Private mode?

With Splash>=2.0, you can disable Private mode (which is “on” by default). There are two ways to go about it:

  • at startup, with the --disable-private-mode argument, e.g., if you’re using Docker:

    $ sudo docker run -it -p 8050:8050 scrapinghub/splash --disable-private-mode
  • at runtime when using the /execute endpoint and setting splash.private_mode_enabled attribute to false

Note that if you disable private mode then browsing data may persist between requests (cookies are not affected though). If you’re using Splash in a shared environment it could mean some information about requests you’re making can be accessible for other Splash users.

You may still want to turn Private mode off because in WebKit localStorage doesn’t work when Private mode is enabled, and it is not possible to provide a JavaScript shim for localStorage. So for some websites (AngularJS websites are common offenders) you may have to turn Private model off.

Why was Splash created in the first place?

Please refer to this great answer from kmike on reddit.

Why does Splash use Lua for scripting, not Python or JavaScript?

Check this GitHub Issue for the motivation.

render.html result looks broken in a browser

When you check http://<splash-server>:8050/render.html?url=<url> in a browser it is likely stylesheets & other resources won’t load properly. It happens when resource URLs are relative - the browser will resolve them as relative to http://<splash-server>:8050/render.html?url=<url>, not to url. This is not a Splash bug, it is a standard browser behaviour.

If you just want to check how the page looks like after rendering use render.png or render.jpeg endpoints. If screenshot is not an option and you want to display html with images, etc. using a browser then you may post-process the HTML and add an appropriate <base> HTML tag to the page.

baseurl Splash argument can’t help here. It allows to render a page located at one URL as if it is located at another URL. For example, you can host a copy of page HTML on your server, but use baseurl of the original page. This way Splash will resolve relative URLs as relative to original page URL, so that you can get e.g. a proper screenshot or execute proper JavaScript code.

But by passing baseurl you’re instructing Splash to use it, not your browser. It doesn’t change relative links to absolute in DOM, it makes Splash to treat them as relative to baseurl when rendering.

Changing links to absolute in DOM tree is not what browsers do when base url is applied - e.g. if you check href attribute using JS code it will still contain relative value even if <base> tag is used. render.html returns DOM snapshot, so the links are not changed.

When you load render.html result in a browser it is your browser who resolves relative links, not Splash, so they are resolved incorrectly.