Recording looks blurry on Youtube but good in Screencastify
For larger recordings it can take a while for higher resolutions to get processed on Drive/Youtube. Directly after uploading, you might only be able to view the recording at a lower resolution. But after a while, HD resolutions will get available for viewing.
If the quality is still to low after HD resolutions get available, this might be because Youtube/Drive may re-encode videos at a slightly different resolution that the one it was originally recorded at.
Usually this isn't an issue, but especially with small text this slight re-scaling might be noticeable. If you wan't to avoid this entirely, make sure to record at a resolution that Youtube/Drive natively supports. The easiest way achieve this with Screencastify is to use the "Resize tab" option with Tab recording as shown below.
This way you'll get a recording at same resolutions and aspect ratio that Youtube/Drive uses.
view on Youtube
Another easy trick to get sharper text, is to zoom in the Chrome Tab a bit before recording (hit CTRL +/-). This way everything will appear larger in your recording. This effectively improves readability of text and will make your recording easier to view on smaller screens as well.