Things wrt IO never seem to stabilize, there is always the N+1 formats. Here is a rundown as of Feb 2026:
- XDMF: currently the preferred format for reading in meshes in parallel, as it uses hdf5 to store heavy data. However, the format has not been maintained since ~2021, and supports limited visualization of higher order fields/DG fields.
- VTX (.bp): Scalable output format similar to xdmf, but uses adios2 for the IO. Not good for reading in meshes, ref: VTK support for unstructured grids with global arrays. · Issue #3688 · ornladios/ADIOS2 · GitHub. Supports higher order visualization of continuous and discontinuous fields.
- VTK (.pvd): store data in many files making it tediuous for large problems and reading in data. Supports the same visualization as VTX.
- VTKHDF (.vtkhdf): the «new» format from kitware. Uses HDF5 with a specific ordering to be possible to visualize in Paraview. Hopefully the future format. Slightly less flexible with respect to multiple grids with different time stepping than xdmf, but supports higher order fields. An initial implementation exists in DOLFINx with a more complex reader/writer (including meshtags) at: Support writing time dependent meshes to vtkhdf by jorgensd · Pull Request #199 · jorgensd/adios4dolfinx · GitHub
- Exodus: old-school format that has implemented some new abstractions in VTK: Discontinuous Galerkin elements and other novel cell-types/function-spaces - Development - VTK . We don’t have a writer for this, as we hope that the DGCell will be implemented in VTKHDF.
The latest update of vtkhdf from kitware is at https://www.kitware.com/vtkhdf-file-format-2025-status-update/