The two things that actually determine quality
A video's quality comes down to two numbers: resolution, the pixel dimensions of the picture, and bitrate, how much data is spent per second to describe it. Instagram decides both when a Reel is uploaded and shared, based on the original file and its own processing. Nothing downstream, including any downloader, can add detail that was never encoded in the first place.
Why the same Reel can come back looking different
Instagram doesn't necessarily keep one single master file per post. Depending on load, region and internal decisions we don't control, its servers can hand back different renditions of the same content at different times. That's why re-downloading the same link an hour later occasionally produces a file with a different resolution or file size than the first time.
Why some downloads use a more efficient format instead of the classic one
For years, most Instagram videos traveled as H.264, a widely compatible format almost every app understands. More recently, Instagram increasingly serves some videos in more efficient formats built for streaming apps, which pack the same picture into a smaller file. They save bandwidth, and most modern browsers and apps play them fine, but a smaller set of basic players, notably some phones' default apps, can't. We wrote a full explainer on that specific problem, including the fix, in our guide on videos that won't open.
Does going through Pullgrab reduce quality?
No. Pullgrab never compresses, re-encodes or otherwise touches the picture itself. It requests the file Instagram makes available for that post and streams it to you unchanged. When it repackages a file, which happens only for the compatibility case described above, it changes the container, not the video or audio inside it.
What actually helps, and what doesn't
There's no toggle, setting or trick, on Pullgrab or anywhere else, that gets you a higher-quality version than the one Instagram's own servers hand back for that specific request. If a Reel looks soft, that's the quality Instagram itself is serving at that moment.