What’s the difference between the ‘Normal’ and ‘Interlaced’ when saving a .gif in Adobe Photoshop?
And which one is better for an image for the web?
when you’re on a slower connection, you got the full effect of waiting for the image to come in. It can be torture sometimes. That’s where the brilliant Interlaced GIF89a idea came from.
Interlacing is the concept of filling in every other line of data, then going back to the top and doing it all again, filling in the lines you skipped. Your television works that way. The effect on a computer monitor is that the graphic appears blurry at first and then sharpens up as the other lines fill in. That allows your viewer to at least get an idea of what’s coming up rather than waiting for the entire image, line by line……Interlaced vs. Non-Interlaced GIF
People don’t like waiting. Today, even 5 seconds is a long time! The advantage of an interlaced image is that a viewer can start seeing the image as a whole (although not clear) from the very start of the page load.