Illegal graffiti refers to unauthorized markings on public or private property, often treated as vandalism and subject to penalties. It becomes illegal when done without the owner's permission, unlike authorized murals or street art. The Canton of Basel-Stadt supports street-art murals by providing designated walls to encourage artistic expression in appropriate locations. Quick removal of unsightly graffiti is crucial to prevent further damage or copycat defacement.

In October 2025, a total of 178 graffiti removals were recorded in the Canton of Basel-Stadt. This included 96 removals from public facilities (SprayEx) and 82 from private buildings (SprayOut). Compared to the average monthly graffiti removals of 142.8 recorded since November 2023, this number is considered to be very high.

The top five communities with the highest number of graffiti removals were Matthäus (26), Altstadt Grossbasel (24), Am Ring (21), Vorstädte (17), and St. Alban (11). Conversely, the communities with the least removals were Breite (1), Riehen (2), Bruderholz (2), Hirzbrunnen (3), and Kleinhüningen (3).

The monthly time series of graffiti removals shows an increase in numbers after October 2023, coinciding with the start of reporting graffiti removals on private buildings (SprayOut). This change explains the observed rise in removals, reflecting the canton’s expanded efforts to address graffiti on both public and private properties.

The Canton of Basel-Stadt is committed to maintaining cleanliness in public spaces. Illegal graffiti on public infrastructure is typically removed within 48 hours of being reported, helping to prevent further vandalism. Residents can report graffiti through a cleanliness hotline or an online form. The canton also financially supports private property owners in graffiti removal, covering a substantial portion of cleaning costs. Additionally, Basel promotes legal street art by providing advisory services, supporting property owners who wish to commission murals, designating walls for legal painting, and encouraging high-quality street art to beautify the city and reduce vandalism.