test your analytics. make sure your own browsing and testing is being properly ignored.
i view my site on every sort of device and every browser i can get my hands on. with max sized windows and really tiny ones.
i use chrome to view the site with a simulated slow connection. don’t ask me how i have to figure it out every time, but it’s in the dev tools somewhere.
there are sites and chrome extensions that allow you to view your site in a simulation of what people see with various forms of color blindness. do that too.
check that videos load and links work. click on everything. there are automated tools for this too — but one last human check is always a good thing and will definitely catch things that an automated tool can’t.
open the dev console in chrome click through your site and look for errors and warnings.
read the copy from top to bottom out loud, this always helps me catch the last few grammatical and copy editing typos.
Also try to find some tools that allow you to check your meta data, page descriptions, etc. in a “bulk” format (rather than page by page.) Sitemap plus can help (Site Organization button) - Meta Mate is (was) great at this but I’m not sure how well it is still supported.
If you are showing on Search Engines make sure the text that is showing is what you want. I am surprised that so many web pages have page titles that don’t make any sense at all or don’t tell what the page is (what showsin browser history, etc.).
The ‘yawn’ bit. Try and get a PC to check all is well on Edge or IE
it’s so tough to do all that platform testing. there really are so many things now. but if you’re trying to reach a broad market then you’ll want to hit all the basics:
iphone mobile safari + a couple iOS versons back if you an find a device for that
remember with mobile to test in both orientations. some folks like to browse in landscape mode
chrome, edge, firefox. remember to test on a very small screen (as well as 1080p) as some of the windows tablets have limited screensizes.
chrome, safari, firefox. yes you should hit firefox. it’s become a good browser again. really, give it a try. i’m using firefox right now. it’s crazy fast.
chrome on mac should just about cover chromium on linux except for the available fonts and a few other random. honestly, i’ve not once tested on linux before launch – and i’m a regular linux user. LOL.
there are some more exotic scenarios like web browsing TVs and such – but these are very market specific and often require herculean effort to get great results – so only go there if you must.
lastly: use chrome or safari dev tools responsive mode to test A LOT of different screen sizes. even just with apple devices there are a simply stunning number of possibilities. there are some destops with smaller screens than some iOS devices there iOS sidebars that a new twist, and zoom modes that change the overall resolution.
an iPhone SE (still currently sold i think) has a screen size of 1136x640 and an iMac Pro has a native resolution of 5120×2880. if i did my math right that’s about 20,000% the number of pixels. your design is going to need to be a bit flexible.
In addition to what @manofdogz said, checking the box on a page by page basis, you can use a robots.txt file on your site.
There are many posts about robots.txt files, the significant advantages are you can keep all the noindex stuff in one place, and Google has a useful testing tool to make sure it works.