What is indexing?

Indexing is the process of looking at files, email messages, and other content on your PC and cataloging their information, such as the words and metadata in them. When you search your PC after indexing, it looks at an index of terms to find results faster.

When you first run indexing, it can take up to a couple hours to complete. After that, indexing will run in the background on your PC as you use it, only re-indexing updated data.

How does indexing make my searches faster?

Much like having an index in a book, having a digital index allows your PC and apps to find content faster by looking for terms or common properties such as the date a file was created. A fully built index can return answers to searches such as "Show all songs by Coldplay" in a fraction of a second, versus the minutes it could take without an index.

What information is indexed?

By default, all the properties of your files are indexed, including file names and full file paths. For files with text, their contents are indexed to allow you to search for words within the files.

Apps you install may also add their own information to the index to speed up searching. For example, Outlook 2016 adds all emails synced to your machine to the index by default and uses the index for searching within the app.

Which apps use the index?

Many of the built-in apps on your PC use the index in some way. File Explorer, Photos, and Groove all use it to access and track changes to your files. Microsoft Edge uses it to provide browser history results in the address bar. Outlook uses it to search your email. Cortana uses it to provide faster search results from across your PC.

Many apps in the Microsoft Store also depend on the index to provide up-to-date search results for your files and other content. Disabling indexing will result in these apps either running slower or not working at all, depending on how heavily they rely on it.

Why does indexing automatically run on my PC at all times?

Your Windows 10 PC is constantly tracking changes to files and updating the index with the latest information. To do this, it opens recently changed files, looks at the changes, and stores the new information in the index.

Where is the index information stored?

All data gathered from indexing is stored locally on your PC. None of it is sent to any other computer or to Microsoft. However, apps you install on your PC may be able to read the data in the index, so be careful with what you install and make sure you trust the source.

How much space is used by the index?

A rule of thumb is that the index will be less than 10 percent of the size of the indexed files. For example, if you have 100 MB of text files, the index for those files will be less than 10 MB.

The index can take up a larger percentage if you have lots of very small files (<4 KB) or if you're indexing computer code. In both cases, the index size will increase dramatically in proportion to the size of the files. If you have lots of small files and need to save space on your PC, consider removing the location of those files from indexing by going to the Indexing Options control panel page and selecting Modify.

What languages can be indexed?

All language packs installed with Windows include the information for indexing content in that language. If you have files or other content in a language that isn't installed on your PC, the index will try to make it searchable, but that isn't always possible.

To install more language packs to make sure the language is searchable on your PC, go to Settings > Time & Language  > Region & language, and then select Add a language .

Which file types can be indexed?

For a list of file types that can be indexed, go to the Indexing Options control panel page and select Advanced > File Types.

Can I change how much of a file's information is indexed?

Yes. There are two options for how much of a file to index: either properties only, or properties and content. For properties only, indexing will not look at the contents of the file or make the contents searchable. You'll still be able to search by file name—just not file contents.

Choosing not to index the contents of files can reduce the size of the index, but it makes files harder to find in some cases.

To choose an option for each file type, go to the Indexing Options control panel page and select Advanced > File Types.