# Assets & Asset Filters

Understand how MK.IO assets map to cloud storage and how asset filters change the manifests delivered to players.

## What is an asset?

An **asset** in MK.IO is a logical pointer to a location in your cloud storage. It is not a copy of your files: it is a reference that tells MK.IO where to find, process, and stream content.

Every asset maps to exactly one storage location:

- **Azure Blob Storage** → a container (or a subfolder within a container)
- **Amazon S3** → a bucket or prefix

The files themselves live in your cloud storage. MK.IO reads from and writes to that location on your behalf. This is why:

- Creating an asset does not move or copy any files
- An asset can appear empty if the storage location is empty or the container name is incorrect
- Deleting an asset in MK.IO can delete the associated files from storage (depending on the deletion setting chosen at creation time)

![Assets Overview](/images/assetfilters.png)

## What goes into an asset?

Assets contain information about digital files stored in cloud storage, including:

- **Source files**: the original uploaded video, audio, or image files
- **Encoded output**: adaptive bitrate segments and manifests produced by encoding jobs
- **Subtitle and caption files**: VTT, SRT, TTML
- **Thumbnails and images**
- **Log files**: generated during processing jobs

On the input side, an **encoding job** or a **live output** references an asset as its source or destination. On the output side, a **streaming locator** references an asset to generate playback URLs.

## Naming files within an asset

File names within an asset must follow both:

- [Azure blob name requirements](https://learn.microsoft.com/en-us/rest/api/storageservices/naming-and-referencing-containers--blobs--and-metadata) and [NTFS name requirements](https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file) (for Azure storage)
- [AWS bucket naming rules](https://docs.aws.amazon.com/AmazonS3/latest/userguide/bucketnamingrules.html) (for S3 storage)

### Reserved characters

The output URL for streaming content is built from the asset file name. File names must not contain any of the following percent-encoding-reserved characters: `!*'();:@&=+$,/?%#[]"`. There can also be only one `.` for the file extension. File names must be 260 characters or fewer.

> **Warning:** Deleting an asset in MK.IO may also delete the underlying files in your cloud storage, depending on the `containerDeletionPolicy` set when the asset was created — `Delete` removes the storage container's contents along with the asset record, `Retain` leaves your files in place. Check this setting before deleting.

## Asset Filters and Account Filters

Filters let you trim the timeline or restrict the tracks and bitrates exposed by a streaming locator without re-encoding the content.

**Asset Filter**: Applied to a specific asset. Lets you define start/end times or filter by track type (video only, specific audio language, etc.) for that individual asset.

**Account Filter**: Applied at the account level and reusable across multiple assets. Enforces consistent delivery rules across your entire library without configuring each asset individually.

Filters are specified by name when creating a streaming locator, and can be combined (asset filter + account filter). See [Create an asset filter](/mkio/how-to/content-management/create-an-asset-filter) for step-by-step instructions.

## See also

- [Reference existing cloud storage](/mkio/how-to/content-management/add-an-asset-in-mkio/reference-existing-storage): Point MK.IO at content already in Azure or S3 and avoid common empty-asset issues.
- [Add assets into MK.IO](/mkio/how-to/content-management/add-an-asset-in-mkio): Overview of all the ways to create assets in MK.IO.