# Meaning of \_definst\_ in links to media files

**URL:** <https://community.wowza.com/t/meaning-of-definst-in-links-to-media-files/45350>\
**Category:** Wowza Streaming Engine\
**Created:** [August 12, 2015, 12:18pm UTC](https://community.wowza.com/t/meaning-of-definst-in-links-to-media-files/45350 "2015-08-12T12:18:30Z")\
**Posts on this page:** 1\
**Showing post:** 1

<div class="post-metadata">

**Author:** ![Anton\_Tremetzberger](https://avatars.discourse-cdn.com/v4/letter/a/f05b48/32.png) [@Anton\_Tremetzberger](https://community.wowza.com/u/Anton_Tremetzberger)\
**Post date:** [August 12, 2015, 12:18pm UTC](https://community.wowza.com/t/meaning-of-definst-in-links-to-media-files/45350/1 "2015-08-12T12:18:30Z")

</div>

Dear wowza community,

I am not shure about the meaning of the “_definst_” in links to media files and I hope you can help me:

I set up a video on demand application called “vod”. If I open a media file, e.g:

```auto
rtmp://[wowza-ip-address]:1935/vod/_definst_/mp4:subfolder/subsubfolder/sample.mp4

```

the file will be played.

If I change the link to e.g.:

```auto
rtmp://[wowza-ip-address]:1935/vod/video123/mp4:subfolder/subsubfolder/sample.mp4

```

the file will also be played. If I remove “_definst_”, the file will not be played, e.g.:

```auto
rtmp://[wowza-ip-address]:1935/vod/mp4:subfolder/subsubfolder/sample.mp4

```

My questions are:

What happens if I use “video123”, “audio123” or any other string instead of "_definst_? Is there any side effect (eg video could not be played in some players or on some devices?) Are there any limitations to the name of the string?

Is der any possibility to remove “_definst_”?

So, the link will be

```auto
rtmp://[wowza-ip-address]:1935/vod/mp4:subfolder/subsubfolder/sample.mp4

```

thank you & best regards,

Anton

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