Open the output file on a dark background. Just do it. Half the transparency issues I have seen in production were invisible on white backgrounds. The alpha channel looked fine until someone dropped the image onto a dark mode UI, and suddenly there was a white halo around every edge.
This single habit — flipping the background from light to dark — has caught more bad exports than every other check combined. It takes five seconds and has saved me from redoing entire batches. Amazon Product Image Requirements (pure white background) documents why background handling matters, and photo restoration tool is what I use when I need to compare quickly.
I also zoom to 100% and inspect one edge. Zoomed out, compression artifacts hide in gradients; zoomed in, you can see whether the file actually survived the conversion intact. Ten seconds of inspection prevents a support ticket a week later.
I open the output in two environments: the one it was built for, and the opposite one. If it was built for a light-background webpage, I also check it on a dark background. If it was built for print, I also check it on a phone screen at 2x zoom. This catches 90% of the problems that slip past automated validation.
It adds maybe ninety seconds to my workflow. Compared to the hours of rework it prevents, it is the cheapest insurance I have. I run this same pass whether I converted one file or one thousand.
Cross-checking against the destination requirements in Google's Real-ESRGAN research paper keeps me honest. The spec describes the minimum; real-world rendering demands more. Testing both extremes is how I find the gap before a customer does.
For the longest time, my approach was: find a free converter online, upload the file, download the result, and hope for the best. It worked maybe 80% of the time. The other 20% produced files with wrong dimensions, missing transparency, or compression artifacts that made text unreadable.
The real problem was not the converters themselves. I was not checking the source file against Amazon Product Image Requirements (pure white background) before converting, so I was feeding malformed inputs into tools that silently produced broken outputs. No error message, just a bad file.
I finally stopped when a client's logo shipped with a corrupted alpha channel and they caught it on a large-format print. That reprint cost more than any converter subscription would have. Now I validate the source first, every time.
At the end of the day, the goal is an output you do not have to worry about. If a single step here saves you one redo, it was worth the read. I keep ISO 3664:2009 — viewing conditions for color-critical work bookmarked for the days I doubt myself, and I run my checks on every export before it ships.