What is Index.noindex in DerivedData? (Xcode's code index)
Quick answer
Index.noindex, inside each project's DerivedData folder, is Xcode's code index: what powers autocomplete, jump to definition, find references and the "Indexing" progress in the toolbar. It's safe to delete; Xcode re-indexes the project in the background, which can take a few minutes on big projects.
Where it is
~/Library/Developer/Xcode/DerivedData/<Project>-<hash>/Index.noindex. One per project.
When to delete it
- Jump to definition or autocomplete stopped working, or shows stale results.
- Indexing seems stuck.
- The project is old and you want its space back (then delete the whole project folder instead).
How
- Quit Xcode. While a project is open, Xcode's indexer keeps files in this folder open.
- Delete the folder for that project, or the whole project folder in DerivedData.
- Open the project again and let indexing finish.
Questions
Will deleting the index lose anything?
No, only the time it takes Xcode to rebuild it.
Why does Xcode keep "Indexing"?
Big projects, many packages, or a corrupted index. Deleting the project's DerivedData folder and reopening is the usual fix.