What is an HDF5 file?

HDF5 (Hierarchical Data Format v5) is a self-describing binary container: groups behave like directories, datasets behave like multi-dimensional arrays, and both can carry arbitrary attribute metadata.

Why are previews truncated?

Datasets are routinely gigabytes (or terabytes). We show the first ~256 values so the page stays responsive. To slice further you'd use h5py, xarray, or PyTables on the original file.

Does this also open .mat (MATLAB) files?

MATLAB v7.3 .mat files are technically HDF5 and many will open here. Older v5/v6 .mat files use a different container — try the MAT viewer for those.

No. h5wasm runs entirely in your browser; the file is copied into the WASM heap and discarded when you leave the page.

Does it work on mobile?

Yes. The tree collapses above the detail panel on narrow viewports, and dataset previews scroll independently.

Scientific.h5 · .hdf5 · .he5

HDF5 viewer

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HDF5 · .h5 · .hdf5 · .he5

Open HDF5 files

Hierarchical scientific data.

Choose a fileor paste · ⌘V

About HDF5

Hierarchical scientific data.

HDF5 is the scientific data format — hierarchical groups, multi-dimensional datasets, rich metadata. It's the on-disk format behind NASA Earth data, NWB neurophysiology recordings, MATLAB v7.3 .mat files, Keras/TensorFlow checkpoints, and a large slice of particle physics output. h5wasm compiles the official HDF5 C library to WebAssembly so we can walk the full hierarchy directly in the browser. The left tree shows every group and dataset; selecting a dataset reveals its shape, dtype, attributes, and the first several values of its data.

FAQ

What is an HDF5 file?: HDF5 (Hierarchical Data Format v5) is a self-describing binary container: groups behave like directories, datasets behave like multi-dimensional arrays, and both can carry arbitrary attribute metadata.
Why are previews truncated?: Datasets are routinely gigabytes (or terabytes). We show the first ~256 values so the page stays responsive. To slice further you'd use h5py, xarray, or PyTables on the original file.
Does this also open .mat (MATLAB) files?: MATLAB v7.3 .mat files are technically HDF5 and many will open here. Older v5/v6 .mat files use a different container — try the MAT viewer for those.
Is my file uploaded?: No. h5wasm runs entirely in your browser; the file is copied into the WASM heap and discarded when you leave the page.
Does it work on mobile?: Yes. The tree collapses above the detail panel on narrow viewports, and dataset previews scroll independently.

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