Here’s a quick trick I learned to compare raster extents in R visually.
r1 <- raster("raster1.tif")
r2 <- raster("raster2.tif")
plot(r1)
plot(extent(r1),add=T,col='blue')
plot(extent(r2),add=T,col='blue')
This will show the extent of both rasters with the first raster being shown in the background.
Quick and easy!