Question

The reason for this “escapes” me.

JSON escapes the forward slash, so a hash {a: "a/b/c"} is serialized as {"a":"a\/b\/c"} instead of {"a":"a/b/c"}.

Why?

Answer 1

JSON doesn’t require you to do that, it allows you to do that. It also allows you to use "\u0061" for "A", but it’s not required, like Harold L points out:

The JSON spec says you CAN escape forward slash, but you don’t have to.

_{Harold L answered Oct 16 ’09 at 21:59}

Allowing \/ helps when embedding JSON in a <script> tag, which doesn’t allow </ inside strings, like Seb points out:

This is because HTML does not allow a string inside a <script> tag to contain </, so in case that substring’s there, you should escape every forward slash.

_{Seb answered Oct 16 ’09 at 22:00}

Some of Microsoft’s ASP.NET Ajax/JSON API’s use this loophole to add extra information, e.g., a datetime will be sent as "\/Date(milliseconds)\/". (Yuck)