The cracked tip of a new fly line. A beginner fly fisher tried casting without a leader and noticed the line made a cracking noise.
The loop is probably still fine, I’d go on using it until something worse happened. Then replace the loop, just the loop.

A fly line cracked at the loop still has plenty of life left in it.

I have a theory! Have you noticed welded loops becoming more and more common on new fly lines?

It seems that anglers like the simplicity of having loops ready made on fly lines. Then, when a welded loop cracks line makers like that anglers assume their line is broken and needs to be replaced. Now this is my theory, so ‘Big Fly Line’ has a sales feature which both sells their lines and which shortens the ‘life’ of a fly line – it’s great marketing!

Damage to a welded-loop is not terminal, never terminal. No fly-line ever died when a welded loop became damaged. We can snip off the loop and attach a braided loop, learn to tie a nail-knot, experiment with shrink tube… there are more options, but these are the simplest. If the fly-line is fairly fresh, we can DIY re-weld the tip… and discover how astonishingly simple it was to make that welded loop in the first place.

Fly lines are consumable., and we will replace them…but maybe not as often as ‘Big fly Line’ likes us to believe.