TopoJSON files are often smaller than GeoJSON and the conversion allows you to incrementally simplify a dataset, if you wish.
Glad you asked, oh handsome OP.
From the command line (Mac OSX 10.8, assumes homebrew installed):
brew install node.js npm install -g topojson
Convert The Data
topojson -o output.json input.json
If you feel better with Python, just install the library by running:
pip install pytopojson
And then run:
python geo2topo.py geojson_file
You can also use a quantization parameter. Just use the
-h argument to see how it works.
Let me know if this was helpful to you!
I have found pretty good online tool for simplifying geospatial data (including GeoJSON) and export to various formats (including TopoJSON) at https://geoprocessing.online/tool/simplify-polygons/. You can upload the GeoJSON, set simplification level and export to TopoJSON. For more information on data size reduction, see this article: https://kb.geoczech.org/knowledge-base/how-to-reduce-size-of-vector-data/