The homeowner's reading room
How to use CookViewer to compare Cook County properties
CookViewer is Cook County's public property map. Use it to check your property record and find similar properties, then review whether the comparisons actually support your research question.
1. Open the official map and find your property
Open the official CookViewer map
This article is an independent walkthrough from Check the County, not the county map itself. In CookViewer, search for your address or PIN and select the matching result. Check the identifier before relying on any values. Our PIN guide can help you find the right number.
The map's built-in Help explains its search and property-detail tools. If your screen differs from this walkthrough, use that current help rather than guessing which control to choose.
2. Open the property comparison tool
CookViewer's help directs users to Compare Properties in the Property Details panel, or the Compare tool in the map toolbar. Your selected property provides the starting characteristics for finding similar properties.
Review the comparison settings for property class, neighborhood, building size, and age. Start with homes that resemble yours. Widening a search can produce more results, but it does not make those properties equally useful.
The Assessor recommends CookViewer in its comparable-property explanation. Review that guidance alongside the map.
3. Compare the facts before the numbers
Make a short note for each candidate: PIN, property type, building size, age, location, and any important difference you can verify. Keep the source and assessment year with the figures. An adjacent property can still be a poor match.
For example, if your home has 1,600 square feet and a candidate has 2,800, write down the difference before comparing their values. Do not treat the lower total assessment as sufficient evidence by itself. This is a hypothetical comparison, not a county rule about acceptable size differences.
The Assessor's residential appeal guidance explains that very different homes will not be accepted as comparables. Check the receiving office's current requirements for your property and tax year.
4. Keep assessments and sale prices separate
An assessed value is a tax-assessment figure. A recorded sale price describes a transaction. Label them separately in your notes and avoid comparing one directly with the other. Our assessment notice walkthrough includes a worked residential example.
A useful worksheet has separate columns for assessment year, assessed value, sale date, and sale price. Leave a field blank when you have not verified it. A price without a date or a value without a year is easy to misuse.
Check the County's free home check focuses on nearby recorded sales. CookViewer helps you inspect property records and comparisons. Neither a map result nor our automated check files an appeal or guarantees a reduction.
5. Save your research and check filing instructions
Keep the candidate PINs, source links, research date, and your explanation of why each property is comparable. Record differences as well as similarities. Do not remove inconvenient facts just to make a comparison look stronger.
The Assessor's current appeal rules explain requirements for comparison evidence and supporting documents. Use the rules for the office where you plan to file; finding properties on a map is only the research stage.
Next, read our comparable-sales guide or check your township's appeal information. Confirm the official filing window before preparing a submission.