Move Peekthru to Applications, open it once, and use Help → Peekthru Help & Quick Look Setup. Enable the extension in System Settings. If another preview extension handles the same format, check the enabled extensions; opening defaults are separate from preview selection.
Common issues
A limit notice means the preview is intentionally bounded. Open the file in Peekthru for richer inspection.
Unsupported HDF5 datatypes and compression filters may prevent value previews. Metadata can still be available. External links and external/virtual dataset storage are deliberately not read.
The HDF5 table displays a selected hyperslab rather than loading a complete large dataset. Indices are zero-based.
Find searches visible notebook content. Reveal outputs or metadata using the notebook toolbar, and reveal per-cell outputs in the cell outline.
Reload with Command-R if a producing application updates or replaces a file. Automatic reload is intentionally avoided while you inspect content.
Unsupported formulas remain source text. Math requires no network connection.
If a recent file moved or lost its permission, select it again through Open.
Reporting a problem
Include Peekthru version, macOS version, processor type, format, and reproduction steps. A small synthetic example is preferable to private or large research files. State whether the issue occurs in the application, Finder Quick Look, or both.