Give a photo the shallow depth of field of a fast lens. The background softens with a gradual, distance-aware falloff so the subject stands out without looking cut out and pasted on.
How the photo background blurrer works
Upload the photo and say how much blur you want, for example 'strong background blur like a wide aperture portrait lens' or 'subtle blur, keep the setting recognisable'. Run the tool and inspect the subject's edges, particularly hair and glasses, where halos show first. If the falloff looks abrupt, ask for a more gradual transition and run again on the same upload.
Tips for the best results
Photos with real distance between subject and background look most convincing. Name the strength in aperture terms or in plain words. Ask for a gradual falloff so nearer background objects blur less than distant ones. Always check hair and thin edges at full size.