Which video quality should you download?
Higher is not automatically better. The right resolution depends on the screen you will watch it on and the connection you are downloading over.
What the numbers mean
The number is the height of the picture in pixels. 1080p is 1080 rows tall, 720p is 720, and so on. More rows means more detail and a proportionally larger file.
Roughly: one minute of 1080p runs 8–12 MB, 720p runs 4–6 MB, 480p around 3 MB, and 360p around 1.5–2 MB. Doubling the resolution roughly quadruples the data, because both dimensions grow.
Match the quality to the screen
On a phone held at arm’s length, most people cannot reliably separate 720p from 1080p, and many struggle to separate 480p from 720p. The screen is small and the pixels are already dense.
On a laptop, 720p is comfortable and 1080p is noticeably crisper. On a television, 1080p is the sensible floor and 4K earns its size on a large panel.
When the highest option is the wrong one
If the source was filmed at 720p, a 1080p version is the same footage stretched. The file is bigger and the detail is not there — no process can add information that was never recorded.
Text-heavy content is the exception worth paying for. Slides, code, spreadsheets and maps become unreadable fast at low resolutions, so take the highest quality available for those even on a phone.