[Qgis-psc] QEP Follow-up Report: Adopt wasm32-emscripten as a build target for QGIS

[Tim Sutton]

Thanks so much for this Michael! I think this also paves the way for us to
start introducing demonstrator projects into QGIS.org so that we can better
showcase QGIS cartography. I have asked Lova to start looking into creating
some initial prototypes.

Regards

Tim

On Mon, Jan 19, 2026 at 11:12 AM Michael Schmuki via QGIS-PSC <
qgis-psc at lists.osgeo.org> wrote:

> Dear PSC
>
> This email serves as the follow-up report for the "Adopt
> wasm32-emscripten as a build target for QGIS" QEP. The implementation
> phase took place between December 2025 and the first half of January
> 2026. Many thanks to Matthias for his contribution to the quest to
> bring QGIS to the browser and for carrying out most of the work.
>
> An update will be posted to the developers list once qgis-js 4.0.0 is
> officially released on npm. And I would love to give an update of the
> project in Laax.
>
> Thanks for supporting this QEP through the grant program.
>
> --
>
> Original QEP Date: 2025/03/10
> Author: Michael Schmuki (@boardend, michael at opengis dot ch)
> Follow-up Date: 2026/01/19
>
> Status
> - Approved: April 28, 2025
> - Discussion: https://github.com/qgis/QGIS-Enhancement-Proposals/pull/335
>
> Deliverables
> - Integration of qgis-js patches into main QGIS repository: Done
> - Adopting wasm32-emscripten as a build target in CMake/vcpkg: Done
> - CI test on Github Actions for Emscripten compatibility: Done
> - New major version of qgis-js based on QGIS 3.44/4.0: In Progress
>
> Upstream Changes
> All patches required for WebAssembly support have been merged into the
> QGIS repository (tracking issue:
> https://github.com/qgis/qgis-js/issues/39):
> - https://github.com/qgis/QGIS/pull/64075 - Make it optional to build
> with EXIV2 (@m-kuhn, merged 2025-11-27)
> - https://github.com/qgis/QGIS/pull/64109 - Add WITH_AUTH (@m-kuhn,
> merged 2025-12-04)
> - https://github.com/qgis/QGIS/pull/64114 - Allow compiling when Qt is
> built without the timezone feature (@m-kuhn, merged 2025-12-06)
> - https://github.com/qgis/QGIS/pull/64175 - Add missing includes
> (@m-kuhn, merged 2025-12-04)
> - https://github.com/qgis/QGIS/pull/64188 - More optional deps - Qt
> Positioning, PDAL (@m-kuhn, merged 2025-12-08)
> - https://github.com/qgis/QGIS/pull/64386 - Make core build with
> Emscripten for WASM (@m-kuhn, merged 2026-01-01)
> - https://github.com/microsoft/vcpkg/pull/49039 - [qtkeychain] fix
> emscripten build (@m-kuhn, merged 2025-12-22)
> - https://github.com/frankosterfeld/qtkeychain/pull/286 - Fix build
> with emscripten (@m-kuhn, merged 2026-01-06)
> - https://github.com/microsoft/vcpkg/pull/48489 - [libpq] explicitly
> disable emscripten support (@m-kuhn,  merged 2025-11-27)
>
> Pending (not yet merged):
> - https://github.com/qgis/QGIS/pull/64469 - WASM fixes and qgis_bench
> tests for browser & Node.js (@boardend, open)
> - https://github.com/qgis/qgis-js/pull/54 - Update to QGIS 4.0
> (@boardend, open (further testing ongoing))
> - https://github.com/microsoft/vcpkg/pull/49429 - [qtbase] Fix
> qt.toolchain.cmake corruption for Emscripten builds (@boardend, open)
> - https://github.com/microsoft/vcpkg/pull/49339 - [qtbase] Add new
> feature wasm-exceptions (@m-kuhn, closed)
>
> Summary of Changes
> - Emscripten build support - Complete integration including CI
> workflow, vcpkg configuration, and toolchain support
> - Optional authentication subsystem (WITH_AUTH) - Makes QCA dependency
> optional with stub implementations when disabled
> - Optional EXIV2 dependency (WITH_EXIV2) - EXIV2 is unavailable for
> Emscripten due to missing inih library support in vcpkg
> - Optional Qt Positioning and PDAL (WITH_QTPOSITIONING, WITH_PDAL) -
> More granular control over dependencies
> - Qt timezone compatibility - Allows compilation when Qt is built
> without timezone support (common in WASM builds)
> - Missing includes - Fixed header includes required for WASM compilation
>
> Outcome
> - QGIS now officially supports the wasm32-emscripten build target
> - All qgis-js patches have been upstreamed - qgis-js no longer
> requires any QGIS patches. This allows for easier creation of new
> qgis-js version in coordination with new QGIS versions.
> - GitHub Actions CI ensures ongoing Emscripten compatibility
> - Foundation laid for future WebAssembly-based QGIS applications
> - Collaboration with upstream (dependency packages) in order to
> improve the ecosystem and create sustainable fixes
>
> Next Steps
> - Release new major version 4 of qgis-js based on upstream QGIS, time
> aligned with QGIS 4.0.0 in February 26 (currently tracked in
> https://github.com/qgis/qgis-js/pull/54)
> - Explore expanded API surface for qgis-js
> - Community exploration of additional WASM possibilities (QGIS
> Processing, PyQGIS in browser, QgsQuick port)
>
> Funding
> The resources allocated through the QGIS Grant 2025 have been fully
> utilized. Development will continue, though the pace may vary
> depending on available funding.
> This is still early-stage work - laying the foundation and solving the
> initial challenges required to bring QGIS to the browser.
>
> --
>
> Michael Schmuki
>
> Full-Stack Developer
> Team QGIS & Industry Solutions
>
> michael at opengis.ch
> opengis.ch
> _______________________________________________
> QGIS-PSC mailing list
> QGIS-PSC at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/qgis-psc
>


-- 

Tim Sutton

*Kartoza Cofounder*Tim is a member of the QGIS Project Steering Committee

*T *: +27(0) 87 809 2702          *E *: tim at kartoza.com          *W* :
kartoza.com



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