- Checkins can optionally contain photos or notes.
- Photos and notes (as comments) can also be added to existing checkins.
- Only the author of the checkin may add photos, but any of their friends may add comments.
- Foursquare provides a web hook that can run every time a user checks in. 
Foursquare supports creating and sharing lists of venues. By default, Foursquare starts you off with a "to-do" list. It is possible to create lists with any name, so there are many examples of lists of favorite places, collecting places to visit in another city, or lists of places that have something in common.
Checkin notes have a length limitation of 200 characters.
Foursquare has feed files and an API that can be used for export.
Foursquare provides feed files of all your checkins in multiple formats: RSS, KML and ICS.
- https://foursquare.com/feeds/ when logged in will show customized feed URLs that use special tokens for access (do not share them)
- Set up a Foursquare Developer account at https://developer.foursquare.com/
- Either write your own script or use the one Michael Owens wrote to extract all of your Foursquare data to your local file system. The script works by connecting to Foursquare, counting how many checkins you have to determine the total number of pages of data it needs to download, and then it makes periodic calls to the Foursquare API to download the files to your local machine or server, staying within the Foursquare rate limits.
- Convert your Foursquare API JSON files into h-entry h-as-checkin files by writing a second script to construct meaningful HTML representations of the checkins. The script mko wrote will handle most of the conversion from a Foursquare JSON object to a h-entry JSON object. Since he uses Indie.js, the script has a decent amount of data relevant only to his purposes at this time, but it would not be difficult to convert the script into a generic converter if needed.
- Michael Owens has exported all his Foursquare checkins, and has also
imported all of my posted photos, likes, and comments, though the likes and comments haven't been converted into IndieWeb mentions yet.
- ... first check-in on werd.io that POSSEd to Foursquare?
If I check in via my site, it'll check me in via Foursquare and ignore the push response for the checkin (so I don't get duplicate checkins).Michael also supports PESOS from Foursquare:
I've got a push endpoint on my site, so anytime I check-in on Foursquare through the app, it'll check me in via my site as well.
Foursquare does some amount of tracking of what events are happening at venues in their venue database.
The result is that others seeing your checkin see that you also checked in at a specific event at the venue, e.g.:
See also analysis of the Foursquare API by Social Web WG:
Foursquare provides the ability for someone officially associated with a venue to "claim" that venue which then gives that person more authority over the venue, including the ability to associate events with the venue (as documented above)
- someone from the venue has to go to https://foursquare.com/venue/claim
- and claim it as a venue they manage
- they make you give a phone number to "receive a call to verify your claim". The call asks you to record a sentence stating your name and relationship to the venue. The call appears to not be manually screened, but presumably is archived.
- they'll either mail you a postcard, or you can pay $1-20 (depending on city) with a credit card to "verify" it