There is indeed a low limit on GET uploads. To solve that, don't use GET. See this stackoverflow question .
Servers may also impose an upload limit, which is usually higher by default (several MBs or more). If that's the problem, you need to check your server configuration and increase the limit, or tell us which server software you use.
EDIT Since your error specifically says url, it's probably not a server configuration issue. But you may run into that later if files get very large.