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HotCakeX's avatar
HotCakeX
MVP
Jan 21, 2020
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Can i please get some explanation and information about the things written in the Local State file?

The file is located here: %localappdata%/Microsoft\Edge SxS\User Data for Edge canary   can be viewed from browser too: edge://local-state/   some of them are obvious like this   "browser": ...
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  • Thraetaona's avatar
    Thraetaona
    Jan 22, 2020

    HotCakeX 

     

    You're welcome, by the way 'EME' stands for Encrypted Media Extensions.

     

    The '"experimentation_and_configuration_service_control"' should be related to the A/B feature rollout as you've mentioned.

     

    '"fre"' Is supposed to state weather the user has seen the splash screen that runs the first time Edge is started, I Assume it stands for something like "First Run Experience"

     

    '"UpdateClientData"' Should be related to syncing the PWA's (apps); Judging by the pattern, it seems like I have the exact fields, although a few more entries. Not sure https://support.google.com/analytics/answer/6158745?hl=en

     

     

    Most chromium fields are equal, if you want further info about the experience metrics, you could find a full list along with comments here: https://chromium.googlesource.com/chromium/src/components/metrics/+/refs/heads/master/metrics_pref_names.cc

     

     

     

     

     

    Regarding CFR's, I remember having random flags added to the browser during the day despite the browser being fully updated. Hard to try and manually add those 'experiments', as the documentations are sparse at the moment.

Thraetaona's avatar
Thraetaona
Iron Contributor
Jan 22, 2020

HotCakeX 

 

 

Those custom policies are enforced to ensure backwards compatibility between the new chromium based edge and legacy EdgeHTML/IE.

 

 

In this case its most likely for proprietary DRM's.

 

In addition to certain user agent overrides, this makes sure that a website built to use a prefixed API will continue working on the new Edge.

 

Browser vendors usually have prefix's for experimental technologies.

 

Consider the new backdrop filter CSS property. (Prefixed and normal) 

 

-webkit-backdrop-filter: blur(5px) saturate(125%);
backdrop-filter: blur(5px) saturate(125%);

 

Both works flawlessly across all major web browsers.

HotCakeX's avatar
HotCakeX
MVP
Jan 22, 2020
Thanks, I also thought that they would be somehow related to user agents but couldn't figure out what "ExposePrefixedEME" was, still can't tbh, is it a built in policy and is there any way to access it to see more details?

also do you know what this part is?
"experimentation_and_configuration_service_control": 2"

I tried playing with it and setting it to 1 or 0 caused some of the controlled feature rollout items in Edge canary to disappear/appear. I couldn't find a reliable pattern for it though

my main reason for learning the specifics in that file is to find a way to enable features that are locked behind CFRs

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