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TopoJSON to GML

TopoJSON to GML Converter Online | GeoDataViewer

Quick answer: Convert TopoJSON to GML online for free. Open your TopoJSON data, inspect the map preview, and download GML output locally in your browser — no upload required. TopoJSON is a topology-aware JSON format that reduces redundancy by storing shared geometry arcs once instead of repeating them for every feature.

Before converting TopoJSON to GML

Prepare the input

Choose a complete TopoJSON dataset (.topojson, .json). Keep required sidecar files together and check the source coordinate reference system.

Know what you download

GML output is downloaded as a file, or ZIP when the driver generates sidecars. Compare the result against the source before sharing.

Limits and troubleshooting
  • Converting TopoJSON to GML can change field types, metadata and presentation. A successful download does not prove every source element survived.
  • Browser memory varies by device. There is no guaranteed unlimited file size; split large datasets or use a desktop GIS when memory or WASM initialization fails.

If something goes wrong

  • Empty or partial preview: confirm the source contains supported vector geometry and compare the source layers with the preview.
  • Wrong continent or distorted geometry: inspect the source CRS, axis order and a known location. Valid syntax alone does not guarantee valid placement.
  • Conversion cannot start: reload while online so processing libraries and WebAssembly can load, then retry a smaller known-good sample. File contents are still processed locally.
  • Incomplete export: compare source/output counts, geometry families and key fields. Inspect warnings and keep the original file.
Source Format Guide

What is TopoJSON?

TopoJSON is a topology-aware JSON format that reduces redundancy by storing shared geometry arcs once instead of repeating them for every feature.

TopoJSON is especially valuable for web-delivered boundary and polygon datasets where neighboring features share edges and repeated coordinates would otherwise bloat the file.

Its topology model makes it efficient for delivery, but many editing and GIS workflows still prefer to convert TopoJSON into ordinary feature collections before working with it.

Common Workflows

Common use cases

  • Country, state, county, district, or service-area boundary layers on the web.
  • Thematic maps where many adjacent polygons share borders.
  • Preprocessed browser assets that need smaller download sizes than plain GeoJSON.
Ecosystem

Where you will encounter it

  • Browser map assets and thematic web cartography.
  • Boundary-heavy data publishing workflows.
  • Developer toolchains that care about compact JSON payloads.
Strengths

Why teams choose TopoJSON

  • Topology-aware encoding can be smaller than equivalent GeoJSON for shared-edge data.
  • Good fit for compact web delivery of boundary layers.
  • Still JSON-based, which keeps it approachable in developer tooling.
Limitations

Where TopoJSON gets awkward

  • Topology adds complexity that many desktop GIS editing workflows do not want directly.
  • Not every conversion target writes TopoJSON, so it often acts as an input rather than a round-trip editing format.
  • Teams commonly need to expand it back into ordinary features before analysis or manual QA.
Conversion steps

How to convert TopoJSON to GML online

  1. 1. Add your TopoJSON file

    Drop the source data into the converter above. Keep any required sidecar files together when your dataset uses them.

  2. 2. Check the map preview

    Inspect the geometry and attributes before exporting so you can spot missing layers or coordinate-system issues.

  3. 3. Download GML

    Run the conversion and save the generated GML output directly from your browser. Your source file stays on your device.

File Structure

Common file extensions and sidecar files

.topojson
Common extension used for TopoJSON documents containing shared arcs and objects.
.json
Generic JSON extension sometimes used when a pipeline does not preserve the more explicit .topojson suffix.
arcs / objects
Core TopoJSON structures that store shared geometry and feature collections separately.
Conversion Rationale

Why convert TopoJSON to GML?

Teams commonly convert TopoJSON into GML when they need an XML-based standards workflow that fits formal data exchange requirements.

  • Teams convert TopoJSON when they need ordinary features for editing, export, or compatibility with tools that do not understand topology-aware JSON.
  • They also convert into TopoJSON when web delivery size matters and the source dataset contains many shared polygon boundaries.
  • GML is commonly used where schema-driven exchange and standards compliance matter more than file size.
  • It is a frequent target in enterprise, government, and specification-heavy environments.
FAQ

Frequently asked questions about TopoJSON to GML

What do I need before converting TopoJSON to GML?

Choose a complete TopoJSON dataset (.topojson, .json). Keep required sidecar files together and check the source coordinate reference system.

What exactly is in the GML download?

GML output is downloaded as a file, or ZIP when the driver generates sidecars. Compare the result against the source before sharing.

How large a TopoJSON file can I convert?

The practical limit depends on browser memory, geometry complexity and the conversion driver. Start with a small sample. There is no guaranteed unlimited size and no cloud fallback or payment tier for large files.

Are my TopoJSON files sent to a server?

File parsing and conversion run on your device. The page, WebAssembly and map basemaps can make network requests; choosing a file does not upload its contents. Load the required libraries before attempting offline work.

Format workflow cluster

More TopoJSON and GML workflows

Use the related viewer, tools, guides, and conversion paths to continue the same GIS task without losing the source format context.