Raster publications provide one alternative to database-based technologies, and despite their limitations, they may be used in the presentation of data having spatial reference. Image browser performance can have a particular impact on the comfort of its use. The aim of the present work is to analyse the relationships between the degree of raster compression and the performance of the map application. The research was carried out in an informal manner, under conditions of typical use, in the form of ad-hoc tests. The measurement was performed using three applications that automate tests: (1) Cloudinary Website Speed Test Image Analysis Tool, (2) GTmetrix, and (3) Dareboost. It has been shown that in applications based on raster maps, which are of an illustrative, temporary and at the same time ad-hoc nature (ad-hoc maps), maintaining high quality images at the expense of application performance is not justified.