Zillow’s Transaction and Assessment Database (ZTRAX)
The Zillow Transaction and Assessment Dataset (ZTRAX) is the nation’s largest real estate database made freely available to U.S. academic, non-profit and government researchers.
Important Notice: ZTRAX Program Ended
With a heavy heart, Zillow has ended the ZTRAX program. While we greatly value independent research and understand that ZTRAX is the only free source of such rich housing data, we could no longer adequately service a growing group of researchers. We are proud to continue our focus on the creation of housing metrics, many of which are free to the public via our website and our API, and on Zillow’s own world-class housing market research.
In accordance with the ZTRAX Access Agreement, researchers must destroy and/or delete raw ZTRAX data from all systems and servers that hold these data by Sept. 30, 2023.
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The Zillow Transaction and Assessment Dataset (ZTRAX) is the country’s largest real estate database made available free of charge to U.S. academic, nonprofit and government researchers. Zillow makes the data — previously inaccessible and/or prohibitively expensive — available in the interest of greater transparency in the real estate market. They are used by dozens of institutions to further research across various disciplines and to address important policy questions.
ZTRAX is updated quarterly and is continually growing. Released data include:
- More than 400 million detailed public records across 2,750+ U.S. counties;
- More than 20 years of deed transfers, mortgages, foreclosures, auctions, property tax delinquencies and more, for both commercial and residential properties;
- Property characteristics, geographic information and prior valuations for approximately 150 million parcels in 3,100+ counties nationwide.
ZTRAX does not contain:
- Zestimates
- Rent data (such as rent prices)
- Listing data (such as time on market)
- User search data
Use of ZTRAX data
To access this real estate database, researchers must be named in a Data Use Agreement (DUA) signed by Zillow and their research institution. Researchers agree to:
- Protect the data from being shared beyond the researchers named in their organization’s DUA.
- Keep the details of their institution’s agreement confidential.
- Per Zillow’s Data Use Agreements, research organizations must provide Zillow with advanced written notice of publication and, unless otherwise instructed, include the following attribution on the first page of the publication, as a footnote or acknowledgement: “Data provided by Zillow through the Zillow Transaction and Assessment Dataset (ZTRAX). More information on accessing the data can be found at http://www.zillow.com/ztrax. The results and opinions are those of the author(s) and do not reflect the position of Zillow Group.” The live link must be live and “followed” whenever technically possible. There also will be a parenthetical citation with Zillow’s name and the year of data was accessed such as “(Zillow, 2020)” on each page where Zillow data are cited.
The following are inappropriate uses of ZTRAX data and will not be permitted:
- Research based on personally identifiable data taken from the public records, or any use of the data to contact or market to individuals.
- Research that combines ZTRAX data with any third-party data source to identify any individual.
- Research done for (or in conjunction with) a commercial enterprise.
- Use for a class project, textbook or other academic endeavor not aimed at publication or policy impact.
- Research not affiliated with a known educational institution, non-profit, government entity or policy organization.
- Use in any combination with any other databases without the correct attribution to ZTRAX.
ZTRAX Support
To provide a dataset with the widest research potential and applicability, all records are delivered essentially unaltered from their original sources. Data quality and availability vary by county. Researchers are responsible for all data cleaning and validating assumptions.
To assist in dataset creation, Zillow has provided example .R code for building a simple hedonic dataset using ZTRAX. We also ask that, in the interest of cooperation, ZTRAX researchers publish a dataset creation code in the living repository to assist future researchers: https://github.com/zillow-research/ztrax.
While we are unable to provide personal support for working with ZTRAX data, you might find useful tips in our FAQ section.
