Why does Squarespace enlarge the file size of an already compressed image?

Hey,
I just got a message from a client ( a photographer)

"....I thought was odd because I limited EVERY file to less tham 740kb at 3000px..This file was showing as 2500px and was saying it was 1.5mb So then I recompressed it and made it 2500px sent it through tiny JPG and got it to 442kb..I uploaded it to Squarespace and now its showing as 666kb…SO squarespace in resizing my images has made them ALL larger which is making the site fail speed test which is certainly going to effect my performance. "
 

That sounded strange so I ran another test myself (screenshot attached)
1) example File I received 2500x2500 with 1.5MB and after compression 442KB
2) Double-checking the compression on tinyjpg.com and Photoshop Webexport
3) I uploaded the file to Squarespace and right-click downloaded it agin and the file was 666kb

Seeme the difference can be even bigger.
 

I'm very concerned. thanks for yor help.



PS: What do you think @paul2009 or @tuanphan
I know Google Page Speed and Squarespace are not best friends but what't the best pratice here?
 

PS: Google Pagespeed recommends to "improve the file size"

5 hours ago, ArminB said:

Squarespace in resizing my images has made them ALL larger

I have seen exactly the same situation on Squarespace 7.1 and believed that a built-in image compression feature had been added to speed up download because images download more quickly and uploading already compressed images made things worse.

However, I was wrong. Further testing showed that the image CDN was doing something strange and undocumented. For example, ?format=original is downloading a 2500px wide image, not the original image. 

I stopped compressing images uploaded to 7.1 because it was counter productive. A compressed image of 715px was downloading as 739px - at a lower resolution. I'm going to contact Customer Support to ask for more information.

I didn't know that, really helpful, thank you @paul2009!!!

Are you sure, @paul2009?

I dropped an un-optimized thumbnail into my 7.1 site and it turned out to be far heavier than the tinyJPG-version. Perhaps are png's and/or thumbnails not optimized by Squarespace?

Thanks Paul.
I appreciate it!

Dear @paul2009
Thanks for this info. So it sounds I'm kind of stuck in a situation on 7.0 with e.g. the Google PageSpeed tool that recommends a heavier file compression?

@rodvaldr It's difficult to say what's going on! I'm logging a ticket with Sqs. Others may want to do the same. 

Was there any reply to this issue. It seem to be really bad.

On 5/15/2020 at 12:24 PM, paul2009 said:

@rodvaldr It's difficult to say what's going on! I'm logging a ticket with Sqs. Others may want to do the same. 

Did you hear anything back? I'm running an AMA on using images with Squarespace this month and it would be great to address this issue. I use JPG mini and had assumed Squarespace must have some enterprise version of a similar application on their servers. 

Any update from Squarespace?

Bump.

Any further news on this?