How to use HDF5 / H5 / NeXus Data Viewer: a practical file-check workflow
Open a real file with HDF5 / H5 / NeXus Data Viewer and check important fields, output, format boundaries, and local privacy.
When to use it
Use this read-only tool when an instrument or program produced H5/NeXus and you only need to verify groups, dataset paths, shape, dtype, and a small value sample. HDF5 is widely used for research, instrument output, and machine-learning data. The viewer reads hierarchy and bounded slices instead of loading entire arrays.
Practical example
In a NeXus file, locate a 2D count matrix under /entry/data, inspect shape=[1024,2048], dtype, and units, then read only [0:100,0:100] as a heatmap. Do not load a multi-gigabyte array for a preview.
Steps
- Choose an HDF5, H5, HDF, NeXus, or HDF5-based NetCDF4 file.
- Expand the group tree and select a dataset.
- Inspect shape, dtype, compression, chunks, and attributes.
- Set a bounded slice for a table, line, or 2D heatmap preview.
Result checklist
- Root groups and expected dataset paths exist
- Shape, dtype, and endianness match the producer contract
- Chunks, compression, and fill value are readable
- Slice bounds match dimensions and CSV export is limited to the current small 2D slice
First troubleshooting checks
A .nc file still will not open
Check the file signature; classic NetCDF3 is not HDF5 and needs a different parser.
The dataset exists but preview fails
It may use a custom filter, object references, or complex compound dtype; keep the source and use HDFView/Python.
Real limitations
- Classic NetCDF3 is unsupported even when the extension is .nc
- Object references, custom filters, and some compound types may not preview
- Large arrays are sliced; whole-database export is unavailable
Privacy and file safety
Parsing runs in the current browser tab and the file is not uploaded to FreeTool to use this tool. Still use a trusted device for customer, engineering, research, or medical material. Keep the original unchanged and clear downloads, screenshots, and browser data after a shared device.