What are these little black dots on my windowsill? With pics

[garlicandsapphires]

Window faces onto a busy road. They look like tiny squashed flies but it’s not that. It’s tacky/ sticky to touch and it appears every few weeks. Have to really scrub to get rid! What can it be?!

Spider poo.

Yes spider poo.

Fly shit

insect/spider 'manure' or mould.

If you wipe it with a damp cloth is the resultant smudge brown or black?
If it's brown I'd say frass (insect/creature poo) if it's black I'd say road/traffic soot.
Usually insect poo appears in clusters though not evenly spread like that.

The windows look like not fully sealed so I’d say it’s soot /pollution coming in from outside,

Spiders have been rubbing their willies on your windowsill

Did you ever find out what it was, I have the same issue but in much smaller amounts.