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.
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.
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:
ZTRAX does not contain:
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:
The following are inappropriate uses of ZTRAX data and will not be permitted:
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.