chronozarr

chronozarr turns a georeferenced raster time series into an interactive dataset that anyone can open with a link. In a web browser, the series plays or scrubs like a video. You zoom and pan the map, and a click on a pixel shows its values over time. In Python, the same files return the exact numbers you stored. No tile server runs anywhere.

Live demo: 117 monthly Sentinel-2 composites of the Ucayali River in Peru, read directly from a storage bucket. Documentation: chronozarr.org.

Quickstart

Install uv, then the chronozarr command:

uv tool install --python 3.13 'chronozarr[geo]==0.4.1'

chronozarr supports Python 3.11 and newer. --python 3.13 makes uv use 3.13 even when an older Python comes first on your computer. With pip, in an environment with Python 3.11 or newer:

python -m pip install 'chronozarr[geo]==0.4.1'

Use a folder with one GeoTIFF per date, with the date in each file name, such as ndvi_2024-01.tif. All files share one grid. To try it without your own files, export twelve months of the public demo as GeoTIFFs:

chronozarr export-cog https://data.chronozarr.org/ucayali_santa_maria_v03 sample --level 2 --times 2024-01..2024-12

Then convert the folder, look at it, and share it:

chronozarr convert sample my_store --dry-run
chronozarr convert sample my_store
chronozarr preview my_store
chronozarr share my_store

The dry run checks every file and writes nothing. convert writes the store. preview opens it in your browser. share prints a temporary link that a colleague opens in a browser; it needs cloudflared and works only while the command runs.

The full quickstart has a sample dataset, the expected output of each command and the pip route.

Share a store

The recipient needs only a web browser. chronozarr.org serves the viewer page and stores no data. See Share a temporary link and Publish a permanent link.

Read the values

import xarray as xr

ds = xr.open_dataset("my_store", engine="chronozarr")

A store is a Zarr v3 group, so xarray, zarr-python and GDAL 3.13 also read it without chronozarr. See Analyze a store in Python.

JavaScript

npm install chronozarr@0.4.1

The npm package has a DOM-free reader, a MapLibre layer, a GeoLibre plugin and the full viewer for self-hosting. See the JavaScript reader.

Versions

The Python and npm packages are 0.4.1. The store format specification is v0.3.0, a draft. A package upgrade does not change existing v0.3 stores. To use a v0.2 store, convert it with chronozarr convert OLD_STORE NEW_STORE. Release notes for 0.4.1.

Documentation

The pages are written in docs/ and published to chronozarr.org. To contribute, see CONTRIBUTING.md.

License

See LICENSE.