Shared edges stored once
Neighbouring polygons reference the same arc rather than each holding their own copy of the boundary between them.
Convert GeoJSON to TopoJSON Online
Convert GeoJSON to TopoJSON so shared boundaries are stored once instead of twice. For ward, village or district layers where neighbours share edges, the file usually comes out dramatically smaller.
GeoJSON from
TopoJSON to
Drag a GeoJSON file here
or
Accepts .geojson, .json · no size limit · nothing is uploaded
POSMove over the map to read coordinates
How to convert GeoJSON to TopoJSON
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1
Choose your GeoJSON file
Drag it onto the panel or browse for it. Several files at once is fine, and each is read straight from your disk rather than uploaded.
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2
Check the preview
Features draw on a map with their attributes. A polygon that came through inside out, or a file that turns out to be empty, shows up here rather than later in QGIS.
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3
Download the TopoJSON
Press download and the file is written straight to your downloads folder. Adjust precision or other settings first if you need to.
What comes across
GeoJSON carries more than geometry, and most converters drop the rest. This one does not.
Attributes intact
Properties travel with the geometries and survive a round trip back to GeoJSON.
Exact coordinates by default
No quantisation unless you ask for it, so nothing moves on the way through.
Frequently asked questions
How much smaller will my file get?
It depends entirely on shared boundaries. A set of adjoining village or ward polygons can drop by half or more, because every shared edge is stored once rather than in both neighbours. A scatter of unrelated points saves almost nothing, since there is nothing to share.
What is quantisation and should I use it?
Quantisation snaps coordinates onto a grid before encoding, which shrinks the file further but moves every point slightly. It is off by default here because survey data should not be moved without you asking. Turn it on for web display, leave it off for anything measured.
Do attributes survive?
Yes. Feature properties are carried onto the TopoJSON geometries and come back intact when you convert the other way.
What reads TopoJSON?
D3 and most web mapping stacks read it directly. QGIS reads it too. If a tool will not take it, convert back to GeoJSON here.
Is my file uploaded anywhere?
No. The topology is built in your browser and never sent anywhere.
All our converters
Every conversion below is live. Pick a starting format and go.
GeoJSON
KML
KMZ
GPX
CSV
Excel
Shapefile
WKT
TopoJSON
GeoJSONSeq
DXF
SVG is an export format only — you can convert any layer into it, but not back out again. A drawn map has no coordinates to recover, only shapes on a page.