F12 preview show me the page but through an iFrame and not the original file

[ZivoDesign]

F12 preview show me the page but through an iFrame and not the original file,

It happened lately and I don't know why instead of loading my local file from my computer it somehow renders it through iframe so when I came to edit it via Dev-Tools I can't really do anything

see image below 

[Nancy OShea · Accepted solution]

Yes, Real-Time / Device Preview uses an iframe.  To disable RTP, go to Preferences and select Default to Static Browser Preview.  See screenshot.

Edit > Preferences > Real-Time Preview

[ZivoDesign]

Thank you  Nancy OShea

Can you explain to me what is the purpose of the RTP

and what are the benefits of RTP over Default to Static Browser Preview

[Jon Fritz]

Real Time Preview is supposed to update the page in the browser as you work in DW, without needing to save your work.

It never worked correctly for a good number of people so Adobe added the option to default to a static preview to the Preferences a few releases back. 

[Nancy OShea]

What Jon said.  And Device Preview is for checking your progress on mobile devices in real-time.   I have a local testing server so I don't need Real-Time Preview.  Static browser preview is all I ever use.