How to control cache of some js files ?

Hello, when I test the performances of my website I am having some errors like this :
cache.PNGWhat should I do ?
SniperCode ShevaAsked:
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None of those are yours so it is not clear what tests you are running and what you hope to accomplish.
The presumption by the analysis is that you have authorship rights of those ,js file, I believe all those .js file have a no-cache directive.
Shalom CarmelCTOCommented:

arnold is right - you do not have any control over these files, in fact they already come with their own cache control directives so a browser does cache them for the time specified in the report.
This file is already cached for 1200 seconds, like the report states. Maybe this report means that cache ttl can be longer, but it is out of your control anyway.

However, you can improve performance by using https in all references to these objects.  responds in a redirect to the same object but via a secure protocol, and using https upfront will improve the cumulative page load time by up to a second in some locations.

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You cannot control external resources. Facebook and Google are always fast to load.
Is the picture from ?
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SniperCode ShevaAuthor Commented:
OK, my OCR works well. You cannot control external resources at all, what you see is that your page resources are configured well. Those are tracking scripts and sites providing them use those short expiry times. You cannot change that at all.
SniperCode ShevaAuthor Commented:
Ah, thank you.
Is GtMetrix the best way to know the performance of a website or do you have another website which can help me more ?
It points configuration issues just fine in easy to assess form. It is free compared to holding a machine across one ocean to meter user experience for one single site.
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