Safari 14 Web Inspector Extremely Slow

Safari 14's web inspector is extremely slow to boot up, laggy, and often crashes the page on my 2016 15" MacBook Pro 2.7Ghz.

It's made my job (web developer) extremely difficult since the issues started first in Catalina. I use Safari because it's the most commonly used browser on my web properties. I was excited for Big Sur because I thought it would resolve the issue as Apple usually does but the issue persists in Big Sur. I think I'm working at a third of the pace I was previously working at. I just want to stress, I'm talking about a really bad lag.

Safari Tech Preview is only slightly better so I've been using that. Please let me know that the issue is acknowledged because I first sent feedback to Apple when Safari 14 was first released and posted on the Apple Community Forums. I've just discovered this forum so I thought I'd try here.

==EDIT==
Happy to add that it's currently in all of its glory.
Here's specific examples:
Open Network Tab and reload to see network transfer details, I'll consistently get "This page was reloaded because a problem occurred." Then it will do that multiple times in a row and I'll get an error page "A problem repeatedly occurred with <URL>." Luckily this is a consistent issue so it should definitely be reproducible for Apple.
What's tremendous is the inspector will still show and look like it's working but it'll be disconnected from the current page and be showing a previous page. I'll have to close it and reopen it which takes about 20 seconds.

Just a small rant: I have been a tremendous advocate for Safari due to its performance, I've been using Safari as my primary browser since 2010/11. Since the Chrome team pulled out, Safari has been slow to adopt new web standards, developing on Safari has now become a pain, and Safari is the most used browser in the US. All credit to the Safari team, Safari still is the best web browsing experience for today's internet, it's faster at the simpler tasks than Chrome, more secure, and uses less memory. But the lack of new feature implementation, developer experience, and being the biggest fish in the pond is a familiar story for any web developer that's been around for Internet Explorer.
Hello h_b, thanks for writing.

It sounds like you are hitting a crash in the page that's being inspected, not in Web Inspector itself. Does this happen for a specific page, or lots of pages? And, does this happen in a recent release of Safari Technology Preview?

Either way, please file a report at https://feedbackassistant.apple.com and we'll take a look. Please include a sysdiagnose and the URL(s) where you are encountering this issue.

Thanks!
BJ
Hi BJ,
Unfortunately, the performance of the web inspector is an issue on most pages I visit. An exception, for example might be google.com or apple.com where the DOM structure is relatively small so the web inspector boots much faster.
However, most websites do not share those qualities.

The issue started in Safari 14.0 in Catalina. I then noticed that Tech Preview was slightly faster (very slightly). I can't speak to whether or not this was a slowdown for Tech Preview but it's still really slow in both Tech Preview and Safari for any use case.

Best,
Henry
Safari 14 Web Inspector Extremely Slow
 
 
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