[PROJ] proj in the browser

[Thomas Knudsen]

Whoa, Javier! That is utterly awesome!

I needed this badly a few months back, when teaching a geodesy course for
people who would never consider installing PROJ on their PC. Next time
around, I will just point them to your work.

Thanks for this huge effort!

/Thomas Knudsen

Den man. 23. feb. 2026 kl. 11.25 skrev Javier Jimenez Shaw via PROJ <
proj at lists.osgeo.org>:

> Hi
>
> TL;DR: go to the links below and play :)
>
> Finally, after a long time and learning a lot during the process, I am
> getting a webpage that uses PROJ to perform coordinate transformations
> (similar to cs2cs), and another that replicates projinfo:
>
> tranform: https://jjimenezshaw.github.io/wasm-proj/transform.html
>
> projinfo: https://jjimenezshaw.github.io/wasm-proj/projinfo.html
>
> All runs in the browser with PROJ (current master as of yesterday), no
> server needed. It uses the wasm compilation with emscripten that is run in
> CI (I copied the two needed files into the project).
> It uses a very simple library to manage the memory allocation, trying to
> make it simple for the javascript developer. The library is still in
> development, but functional as you can see.
>
> The transformer is able to use grids: it downloads at execution time the
> part of grid needed (a feature PROJ already has). For that it needs some
> code to run in a web worker, but the library is doing that as well.
>
> For instance, this link
> https://jjimenezshaw.github.io/wasm-proj/transform.html?st=combo&tt=combo&sh=EPSG%3A6318&th=EPSG%3A6539&tv=EPSG%3A6360&p3d=1&net=1&coords=40.7789978+-73.9632654+-20.5
> uses the geoid model for NAVD88 (in this case, GEOID18)
>
> Tip for projinfo: add "&run=1" when you share the URL, and it will run
> directly the query. Both pages update the URL with the data to make it easy
> to share.
>
> Have fun!
>
> Cheers,
> Javier.
>
> PS. Yes, another one. There are at least two other. This was a personal
> challenge to efficiently use the grid files in the browser.
> PPS. Why these two, and not other things from PROJ? well, these are the
> two apps I use in a daily basis in the console. Now I can send a link to my
> colleagues that do not know how to use the command line. But more things
> can be done.
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