IL HB5871

Prohibits landlords from using algorithmic devices that incorporate or were trained with nonpublic competitor data when setting residential rent amounts or determining rent increases for lease renewals.

Defines "algorithmic device" as a tool using algorithms to calculate rental pricing data, but excludes monthly trade association reports with aggregated anonymous data and products used for affordable housing program guidelines.

Defines "nonpublic competitor data" as information not widely available to the public, including actual rent prices, occupancy rates, and lease dates derived from competing landlords.

Classifies violations as unlawful practices under the Consumer Fraud and Deceptive Business Practices Act.

Applies to all residential rental agreements executed on or after the bill's effective date.