Illegal graffiti refers to the unauthorized marking of public or private property and is commonly treated as vandalism, often subject to fines or other penalties. Graffiti becomes illegal when it is created without the owner's permission, whereas works produced with consent, such as approved murals or street art, are considered legal. The key distinction therefore lies in the authorization of the property owner. Unsightly or unwanted graffiti should be removed as quickly as possible to prevent further damage or copycat defacement. At the same time, the canton of Basel-Stadt actively supports the creation of street-art murals by providing designated walls and encouraging artistic expression in appropriate locations.

In May 2026, a total of 110 graffiti removals were recorded. This total is broken down into 49 removals from public facilities, categorized as SprayEx, and 61 removals from private buildings, categorized as SprayOut. Compared to the average monthly graffiti removals of 147.2 recorded since November 2023, this number is considered to be high.

The top five communities with the highest number of graffiti removals in May 2026 were St. Johann (15), Matthäus (14), Wettstein (13), Am Ring (11), and Vorstädte (11). The bottom five communities, where the least removals were required, were Kleinhüningen (1), Bruderholz (2), Rosental (2), Breite (2), and Bachletten (3).

The monthly time series of graffiti removals shows a notable trend. From 2018 through most of 2023, monthly removals typically ranged between 30 and 90, with occasional spikes. A significant and sustained increase began in November 2023, when removals jumped to 200. This level has generally been maintained, with monthly totals often exceeding 130 and reaching as high as 212 in March 2026. This increase is explicitly explained by the fact that reporting of graffiti removals on private buildings, the SprayOut category, only started in October 2023. The inclusion of these private building removals accounts for the higher overall numbers observed after that date.

The Canton of Basel-Stadt maintains cleanliness in public spaces through a dedicated approach. Illegal graffiti on public infrastructure is typically removed within 48 hours of being reported, which helps prevent further vandalism. Residents can report graffiti through the cleanliness hotline or by completing the online form. Additionally, the canton financially supports private property owners in removing graffiti, covering a substantial portion of cleaning costs. Basel actively 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 as a way to beautify the city and reduce vandalism.