I think I made a mistake and would like to see the map before a certain change set, is that possible?
(or am I thinking too much in GIT terms now… ?)
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Yes, with achavi - Augmented OSM Change Viewer [attic] you can see how streets/buildings/areas were drawn before, deleted/added nodes. Just suffix your change set number at the end of the given link. Click on or mouse hover over the object and it will tell the tags before and after.
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ok thank you 
Overpass can render the map of a certain date, see Overpass API/Overpass API by Example - OpenStreetMap Wiki.
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If you’re comfortable with installing the OSM map style, I made a tool to generate these images easily: GitHub - amandasaurus/osm-mapping-party-before-after: Generate images of an area in OSM before & after, to show your mapping progress
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Thank you all for the feedback, I’ll try these options