Identify pale fringes around a removed background and choose between a better source, manual edge repair or a different composition.
Understand the mixed edge
At a soft boundary, one pixel can contain both subject and background color. If the original background was white, that mixed color may remain after the model changes the pixel's transparency. This creates a pale fringe when the cutout is placed on a dark surface. A halo is therefore not always a strip of fully retained background.
Diagnose with a contrasting color
Choose a dark custom background and inspect the edge. Compare the same region in the original. Look particularly around hair, fabric and motion-blurred contours. Then switch to white: if the defect nearly disappears, a background-colored fringe is a likely explanation. A white outline added intentionally is different; set White subject outline to Off while diagnosing.
Choose a repair proportionate to the job
For a small graphic on white, the fringe may not be visible at the actual output size. For a dark thumbnail, choose a cleaner source or use an editor with edge color correction and masking controls. Cropping the mask inward can remove useful detail, so it needs careful review rather than an aggressive global adjustment.
Reprocessing a downloaded cutout does not guarantee fringe removal. Keep the original available and inspect the final PNG on the actual destination color. A preview that looks good on the checkerboard is only one test, not evidence that the edge works everywhere.