# Searching Across Multiple Files

A single document is easy to search once you have opened it. Multi-file search lets you
ask a question across every document in your library at once, so you do not have to open
each file individually to find what you need.

## Searching across your library

Start a search from your library instead of from a single document. Keyline searches
every processed file at once and returns the passages, figures, and tables most relevant
to your question, each with a citation back to its source document and page.

## How the multi-file index works

Every file you upload is added to a shared search index as part of
[processing](/docs/keyline/getting-started). This index is what makes cross-file search
fast: instead of re-reading every document at search time, Keyline searches the index and
then confirms the most relevant matches directly against the source pages.

## Grouping results into bundles

When a search turns up a useful set of files, you can group them into a bundle so you can
come back to that same set later without searching again. See
[Organizing your library](/docs/keyline/organizing-your-library) for more on bundles.