Observed arrival · 2026-09-29

Mosaic, a redistricting program

mosaicapp.org Visit website

Editorial interest 78/100 Selection signal · not a rating of the site

Mosaic is desktop software for computer-assisted redistricting, using recombination and simulated annealing to explore district maps.

Landing page captured for the 2026-09-29 issue.

For: People creating or refining district maps
Worth noticing: Mosaic normally redraws two neighboring districts at a time, with optional three-district moves and single-precinct flips.

Field notes

The described workflow starts with a shapefile and user-selected goals, then updates a live map while the search tries proposed district changes. Users can inspect score histories and district metrics, compare goals that align or compete, and return to the best plan found during a run. The page says assignments and metrics can be saved as CSV, with map exports in PNG or PDF; installation is offered for Windows 10/11 and Apple Silicon Macs.

Observed signals

Read the marks

Editorial observations of this landing page, not a rating.

○OpenPublic substance visible

✦PrettyNotable craft visible

●ProPolished or operationally mature

◎NicheUnusually specific use

◉HumanPersonal, local, civic, or handmade

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