Web video codec guide - Web media technologies
loss of sharpness the act of removing data in the process of encoding video requires that some details be lost.
... if enough compression is applied, parts or potentially all of the image could lose sharpness, resulting in a slightly fuzzy or hazy appearance.
... lost sharpness can make text in the image difficult to read, as text—especially small text—is very detail-oriented content, where minor alterations can significantly impact legibility.

BiquadFilterNode() - Web APIs
q: the sharpness of the phase transition at the center frequency.

CanvasRenderingContext2D.imageSmoothingEnabled - Web APIs
set this property to false to retain the pixels' sharpness.

MediaTrackConstraints - Web APIs
sharpness a constraindouble (a double-precision integer) specifying the intensity of edges.

Image file type and format guide - Web media technologies
it's particulary useful for photographs; applying lossy compression to content requiring sharpness, like diagrams or charts, can produce unsatisfactory results.