Generate unique ID for URL

[Richard]

So the use case - I'm storing webpages on disk and want a quick retrieval system based on URL. 
I can't store the files in a single directory because of OS limitations so have been using a sub folder structure.
For example to store data at URL "abc": a/b/c/index.html
This data is also viewed locally through a web app.

If you can suggest a better approach I would welcome it.