Regardless of whether the home is for sale, if you type any street address into Zillow, Redfin, or Trulia, they will often tell you the square footage, the last-sold-date, the taxable value, and often some other official information. Here is one example address across all three services:

Has anyone had any luck reproducing their underlying data? I'm not so concerned with getting up-to-the-minute home sales. If data are a few years old, that's no problem for my purposes. It would just be nice to have basic structural data nationwide like: address square footage last sold date sale value tax assessment number of bedrooms

I suppose I could write scraping algorithms for all of the counties with recorder databases online, but did Redfin/Zillow/Trulia all seriously show up at all of the other county recorder offices and scan things in by hand?

I found a bit of discussion, most of it makes me think this would be a massive undertaking:

  • Here are one, two uninspiring discussion threads on the topic of where these three websites pulled these data from.

  • Here's an eight-year-old blog post saying that pulling this information is hard.

  • Here's a website that appears to point to all 3,000+ county recorder of deeds pages.

  • They likely get their data from an MLS... at least the asking prices. The property prices may be based in part by state assessment records. – Joe May 13 '14 at 16:26
  • Good question. Out of curiosity, is there something you're hoping to accomplish by reproducing the data that you can't by just using the Zillow / RedFin / Trulia developer API? – UpQuark Apr 10 '15 at 18:25
  • @UpQuark howdy. i want a nationwide data set, not specific queries for specific addresses. is there a way to download everything from the api? one neighborhood of addresses isn't too useful. – Anthony Damico Apr 10 '15 at 23:19
  • Conceptually, you could use an API to rip their data, but that definitely violates their ToS and dev APIs generally have use limits to curtail this. However, depending on what you're doing, you can probably just use their API to create queries in the same way as you would if you had that info in a local DB. What sort of queries are you expecting to make? Very large scale stuff might be a little tricky, but not impossible. There is data that you can request at city / neighborhood levels and you could use this to acquire data from all of the U.S. (or a representative sample) – UpQuark Apr 16 '15 at 15:27
  • @UpQuark let's just say i wanted the most recent sale price of every dwelling in the country. or the taxable value. whichever is easier. – Anthony Damico Apr 16 '15 at 15:33

I don't know specifics on how Zillow, etc acquired their data - other than assuming they (or 3rd party) obtains the data on a per county basis.

As cities/counties open up open data portals, this data will become more accessible to developers.

When searching these portals, you want to look for tax lots, property tax, or parcels.

A lot of these datasets are still in Shapefile formats, but some are being provided in more readable formats (CSV). Some examples:

Denver, CO
http://data.denvergov.org/dataset/city-and-county-of-denver-parcels

Madison, WI
https://data.cityofmadison.com/Property/Assessor-Property-Information/u7ns-6d4x

New York, NY
http://www.nyc.gov/html/dcp/html/bytes/dwn_pluto_mappluto.shtml

Vancouver, BC
ftp://webftp.vancouver.ca/OpenData/csv/property_tax_report_csv.zip

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