Search indexing in Windows

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.

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 the correct music files for the search term "Beethoven" in a fraction of a second, versus the minutes it could take without an index.

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 adds all emails synced to your machine to the index by default and uses the index for searching within the app.

Many of the built-in apps on your PC use the index in some way. File Explorer uses 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 when running in offline mode.

Your Windows 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.

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.

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 Settings  > Privacy & Security > Searching Windows > Advanced indexing options, select Modify.

Yes! To improve your search results, Copilot+ PCs perform semantic indexing along with traditional indexing. Supported file formats include .txt, .pdf, .docx, .doc, .rtf, .pptx, .ppt, .xls, .xlsx for documents and .jpg/.jpeg, .png, .gif, .bmp, .ico for images. Semantic indexing makes your searches more powerful since items that are close and related to your search terms would also be included in your search results. For instance, if you searched for pasta you might also get results for lasagna, including images that contain pasta or lasagna.  

All data gathered from semantic indexing is stored locally on your PC. None of it is ever sent to Microsoft or used to train AI models. Semantic indexing is enabled by default on Copilot+ PCs. If you want to disable indexing and searching for specific locations or file types, you can do so by selecting the appropriate options under Settings  > Privacy & Security > Searching Windows > Advanced indexing options.

The traditional indexing and search continues to work seamlessly for all supported language packs on Windows. However, the improved search is optimized only for these languages: English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified). 
The following table can be a good reference on what to expect from Windows Search across languages: 

System language	Search input language	Indexable content language	Search results
English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	Improved (semantic + lexical)
All other languages	English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	Improved (semantic + lexical)
English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	All other languages	Traditional (lexical)
English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	All other languages	English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	Traditional (lexical)​​​​​​​
English (US, CA, AU, GB), French (FR, CA), German (DE), Spanish (ES, MX), Japanese (JP) & Chinese (Simplified)	All other languages	All other languages	Traditional (lexical)
All other languages	All other languages	All other languages	Traditional (lexical)

For a list of file types that can be indexed, go to Settings  > Privacy & Security > Searching Windows > Advanced indexing options, select Advanced, then select the File types tab.

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 Settings  > Privacy & Security > Searching Windows > Advanced indexing options, select Advanced, then select the File types tab.