"Acid3, in particular, contains some controversial tests and no longer reflects the consensus of the Web standards it purports to test" acidtests.org

The only difference I get when comparing Firefox Quantum to Chrome stable on Linux (updated Arch) is Test 71, which takes too much time in Firefox and thereby gets a 'warning'.

Obviously, you need to be on Firefox Quantum to see its test results. You can click the A to see test failures (Shift-Click it to open in a new tab).

Edit: I get a 97/100, with the following errors:

  Failed 3 of 100 tests.
  Test 23 failed: expected '14' but got '5' - wrong exception for createElementNS('null', ':div')
  Test 25 failed: wrong exception
  Test 26 passed, but took 50ms (less than 30fps)
  Test 35 failed: expected '0' but got '1' - root element, with no parent node, claims to be a :first-child
  Test 69 passed, but took 2 attempts (less than perfect).
  Test 71 passed, but took 214ms (less than 30fps)
  Total elapsed time: 1.57s

On my Android I see this: https://drive.google.com/file/d/1V7LHP1arMMEKnCaPIWjZvZKFhq1...

That's the same score I get on Ubuntu 14.04/amd64 with Firefox 56 though. Let's see what I get after the update...

After the update, I get 97/100 - That's +2/100. BTW it does feel a lot snappier.

Chrome also is failing at 97/100

Safari also fails at 98/100

Opera used to pass the Acid3 test.

And that version has been discontinued, the team disbanded, etc.