Reddit’s Secret API

John Musser, November 25th, 2008

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Every now and then a sharp developer uncovers a clue that leads to discovery of an undocumented, but quite real, web API. A case in point is the folks over at SEO services company Indexed Content, who noted in their blog yesterday that the popular social news web site Reddit has an API. But don’t go looking for any documentation, because it doesn’t look like there is any, at least not yet (for reference we’ve created a Reddit API summary in our directory and will update it if/when this becomes an officially supported API).

How did they find it?

Over the past few weeks I have been working on creating a tool to gather some social media metrics to track social media optimization campaigns. Friendfeed is your friend if you’re embarking on the same project. While looking for a native reddit API however I stumbled across a post on code.reddit.com that mentioned an API endpoint.

The post in question at code.reddit.com gives essentially all the documentation there is at this point:

In many applications, such as Socialite, it is valuable to look up information about a link on reddit. Currently, there are two good ways to do this using the JSON API:

Info call
Example: http://www.reddit.com/api/info.json?count=1&url=STORYURL

The API “info” call is an ideal way to look up reddit stories by URL. However, in some cases, looking up stories by URL alone presents problems:

1. URLs are not mapped to stories on a one-to-one basis. Since the same URL can be posted to many subreddits, when looking up stories by a URL, it becomes necessary to constrain the search by subreddit, e.g.: http://www.reddit.com/r/subreddit/api/info.json?count=1&url=STORYURL

This summary sufficies in many ways given how simple the REST-based API itself appears to be. It returns data in JSON and requires no authentication. Clicking on this link will get you the JSON-formatted version of Reddit’s page to A list of average IQ’s per occupation.

Are there other endpoints? A couple of quick tests to api.reddit.com, a url not documented anywhere, does indeed return a JSON-formatted representation of the current home page HTML contents. There may be more here from Reddit coming soon? In the meantime, guessing the wrong parameters gives the message below.

And in the world of Web mashups this type of discovery is part of a time honored tradition. Two years ago Niall Kennedy reverse engineered the Google Reader API. And it dates all the way back to the prototypical mashup HousingMaps in which Paul Rademacher reverse engineered the Google Maps service back in early 2005 before there was an “official API”. At the time it was just a set of underlying JavaScript functions that he dug through and built on. Google ultimately turned this hacking to their advantage, both by hiring Paul and turning those JavaScript functions into what’s become the most famous and successful of web APIs.